TY - JOUR A1 - Scheurell, K. A1 - Hoppe, E. A1 - Brzezinka, Klaus-Werner A1 - Kemnitz, E. T1 - Bulk and surface properties of highly dispersed VOx/ZrO2, VOx/SiO2 and VOx/TiO2/SiO2 systems and their relevance for propane oxidation N2 - Highly dispersed vanadium-doped metal oxides such as VOx/ZrO2, VOx/SiO2 and VOx/TiO2/SiO2 with vanadium contents between 0 and 25 mole% were prepared by special bulk preparation methods (coprecipitation and sol–gel, followed by freeze-drying). Bulk and surface properties of the obtained mixed oxide solid solutions were thoroughly investigated by different analytical methods (Raman and FTIR spectroscopy, TPD, H2-TPR, oxygen isotope measurements etc.). Moreover, the catalytic behaviour of the oxides was studied for the example of the oxidative dehydrogenation (ODH) of propane to propylene. Independent of the preparation method, the catalytic behaviour of vanadium-doped ZrO2 and TiO2 phases is very similar. Both metal oxide solid solutions are very active in propane ODH whereas the catalytic activity of VOx/SiO2 is relatively low. On the other hand, the reduction of the catalytic activity is accompanied by an improved selectivity for the formation of propylene. The correlation between the catalytic activity and the acidity of the oxide systems is discussed. Oxidation experiments with 18O2 clearly show that the ODH reaction occurs according to the Mars–van Krevelen mechanism. KW - Vanadium-doped metal oxides KW - Solid solutions KW - Coprecipation KW - Sol-gel-method KW - Propan oxidation KW - Catalytic activity KW - Oxygen mobility PY - 2004 DO - https://doi.org/10.1039/b402924k SN - 0959-9428 SN - 1364-5501 VL - 14 IS - 16 SP - 2560 EP - 2568 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-4152 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wiedemann, H. G. A1 - Brzezinka, Klaus-Werner A1 - Witke, Klaus A1 - Lamprecht, I. T1 - Thermal and Raman-spectroscopic analysis of Maya Blue carrying artefacts, especially fragment IV of the Codex Huamantla N2 - Maya Blue, a pigment composed of very low concentrations of natural indigo and the clay mineral palygorskite, is one of the most brilliant blue dyes, intensively used for more than 2000 years in Mesoamerica. It is extremely stable against environmental attacks and was applied by the Indians for inside and outside mural paintings, ceramics, textiles and for colouring their famous codices. In the present paper it was studied as a powder (compared with modern synthetic indigo) and as colour on tissues, a Maya clay head, and fragment IV of the famous Codex Huamantla. Investigations using Raman spectroscopy in the visible and near-infrared range showed a high degree of correspondence among all Maya Blue-carrying samples and a good agreement with synthetic indigo. Additional spectral lines may be explained by a transformation of the planar indigo molecule when binding to the palygorskite lattice. Thermal investigations of the original “amatl” paper of the codex and of recent paper from fig-trees showed a high similarity and thus proved that this tree was chosen for paper making by Mayas, Aztecs and other Indian tribes. This was also true for the codex. KW - Art KW - Codices KW - Differential scanning calorimetry KW - Mesoamerica KW - Raman spectroscopy KW - Thermogravimetry PY - 2007 SN - 0040-6031 SN - 1872-762X VL - 456 IS - 1 SP - 56 EP - 63 PB - Elsevier CY - Amsterdam AN - OPUS4-14794 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brzezinka, Klaus-Werner A1 - Wachsmann-Hogiu, S. A1 - Dreyer, J. A1 - Elsaesser, T. A1 - Werncke, W. A1 - Vodchits, A.I. T1 - Ultrafast intramolecular electron transfer studied by stationary vibrational and time-resolved resonance raman spectroscopy combined with ab initio calculations PY - 2000 VL - 1 PB - Transworld Research Network CY - Trivandrum AN - OPUS4-1032 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mach, Reinhard A1 - Klotz, Hans-Dieter A1 - Oleszak, Franz A1 - Maneck, Heinz-Eberhard A1 - Goering, Harald A1 - Brzezinka, Klaus-Werner T1 - Synthesis and characterization of nanoscaled and nanostructured carbon containing materials produced by thermal plasma technology N2 - Single-walled carbon nanotubes (SWNT) and carbon nitride films are synthesized by a direct current (dc) arc discharge at slightly reduced pressure and by an inductively coupled r.f. plasma (ICP) at atmospheric pressure, respectively. By treatment with nitric acid SWNT are purified from by-products and characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. ICP allows the deposition of carbon nitride films on steel substrate. The deposition of the films creates a relatively strong radial symmetric profile. The structure of the films are rather independent of the distance between substrate and plasma. Raman, Fourier transform infrared (FTIR), and energy dispersive X-ray (EDX) spectroscopy are used for analyzing the carbon nitride materials. T2 - 11th Conference on Applied Surface Analysis (AOFA) CY - Leipzig, Germany DA - 2000-09-24 KW - Single-walled carbon nanotubes KW - Carbon nitride films KW - Arc discharge KW - Inductively coupled r.f.plasma PY - 2001 DO - https://doi.org/10.1016/S0169-4332(01)00253-7 SN - 0169-4332 SN - 1873-5584 VL - 179 IS - 1-4 SP - 1 EP - 7 PB - North-Holland CY - Amsterdam AN - OPUS4-1023 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brzezinka, Klaus-Werner A1 - Trunschke, A. A1 - Hoang, D. L. A1 - Radnik, J. A1 - Brückner, A. A1 - Lieske, H. T1 - Transition metal oxide/carbon composite catalysts for n-alkane aromatization: Structure and catalytic properties N2 - Nanocrystalline particles of high temperature pretreated titania, zirconia or hafnium oxide, embedded in a carbon matrix, have been found to catalyze the aromatization of n-octane into ethylbenzene (EB) and o-xylene (OX) with high selectivity. The carbon matrix itself is catalytically not active, but seems to co-operate with the transition metal oxides in such a way that the various metal oxide/carbon composite materials exhibit equal selectivity patterns. In detail, the carbon component stabilizes a high dispersion of the oxides during the high temperature pretreatment procedure. This thermal treatment results in a destruction of surface acidity of the oxides, which would otherwise be responsible for undesirable consecutive and parallel reactions. Moreover, the carbon component is involved in the deep dehydrogenation of alkanes to multiple unsaturated alkenes. This is explained by the ability of surface carbon atoms to interact with hydrogen. The bulk and surface structure of the catalysts have been characterized by XRD, specific surface area measurements, XPS, UPS, Raman spectroscopy, in situ ESR and DRIFT spectroscopy. KW - Aromatization KW - Dehydrocyclization KW - n-Octane KW - Monofunctional catalysts KW - Zirconia KW - Titania KW - Oxide/carbon composites PY - 2001 DO - https://doi.org/10.1016/S0926-860X(00)00736-5 SN - 0926-860X SN - 1873-3875 VL - 208 IS - 1-2 SP - 381 EP - 392 PB - Elsevier CY - Amsterdam AN - OPUS4-1083 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Geißler, Heinz A1 - Peuker, Christel A1 - Brzezinka, Klaus-Werner A1 - Gaber, Martin A1 - Kohl, Anka T1 - OD bands in the IR spectra of a deuterated soda-lime-silica glass PY - 2001 SN - 0946-7475 VL - 74 IS - 7 SP - 210 EP - 214 PB - Verl. d. Dt. Glastechn. Ges. CY - Offenbach AN - OPUS4-1146 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kozich, V. A1 - Werncke, W. A1 - Dreyer, J. A1 - Brzezinka, Klaus-Werner A1 - Rini, M. A1 - Elsaesser, T. T1 - Vibrational excitation and energy redistribution after ultrafest internal conversion in 4-nitroaniline N2 - Nonequilibrium vibrational excitations of para-nitroaniline (PNA, 4-nitroaniline) occurring after internal conversion from the photoexcited charge transfer state are studied by picosecond anti-Stokes Raman scattering. Vibrational excess populations with distinctly different picosecond rise and decay times are found for a number of modes with frequencies between 860 and 1510 cm–1, including the overtone of a non-Raman active mode. A nonthermal distribution of vibrational populations exists up to about 6 ps after photoexcitation. The time-resolved experiments are complemented by steady-state infrared and Raman measurements as well as calculations based on density functional theory, providing a detailed analysis of the steady-state vibrational spectra of PNA and two of its isotopomers. A weakly Raman active vibration at about 1510 cm–1 displays the fastest rise time and a pronounced excess population and—thus—represents the main accepting mode. We suggest that an out-of-plane mode giving rise to the overtone Raman band at this frequency acts both as coupling and accepting mode in the internal conversion process. PY - 2002 DO - https://doi.org/10.1063/1.1482698 SN - 0021-9606 SN - 1089-7690 VL - 117 IS - 2 SP - 719 EP - 726 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-1637 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Richter, M. A1 - Trunschke, A. A1 - Bentrup, U. A1 - Brzezinka, Klaus-Werner A1 - Schreier, E. A1 - Schneider, M. A1 - Pohl, M.-M. A1 - Fricke, R. T1 - Selective Catalytic Reduction of Nitric Oxide by Ammonia over Egg-Shell MnOx/NaY Composite Catalysts N2 - A novel composite catalyst system for the selective catalytic reduction (SCR) of NOx by NH3 is described operating at temperatures lower than 470 K in the presence of water with NO conversions of 80–100% at space velocities of 30,000–50,000 h-1. The catalyst is prepared by egg-shell precipitation of MnO2 on the external surface of zeolite NaY. Structural and thermal stability of precipitated MnO2 as well as of the MnO2/NaY composite catalyst were characterized by N2 adsorption, X-ray diffraction, laser Raman spectroscopy, temperature-programmed reduction, and electron microscopy. MnO2 precipitated on zeolite NaY (15 wt% loading) retained its amorphous state up to calcination temperatures of 775 K. The zeolite component remained structurally intact. Calcination at higher temperatures destroyed the zeolite structure and transformed MnO2 into Mn3O4. DRIFT spectroscopic investigations revealed the presence of symmetric O=N—O—N=O species formally corresponding to N2O3 on the composite catalyst after contact with NO. Catalytic measurements under integral flow conditions showed that the catalyst performance is associated with a close coupling of nitrite formation and its drain off from equilibria with NO/NO2 and nitrate by ammonia. Several results are in line with the “diazotation” mechanism, including NH3 protonation to NH4+, whereas prevailing Lewis acid sites should enable NH3 activation via amide species, thus leading to a parallel “amide/nitrosamide” SCR reaction route. The activity-temperature profile fulfills the requirements of a low-temperature NOx reduction catalyst for mobile diesel engines if an ammonia supply is implemented “on board,” e.g., by urea decomposition. PY - 2002 DO - https://doi.org/10.1006/jcat.2001.3468 SN - 0021-9517 SN - 1090-2694 VL - 206 SP - 98 EP - 113 PB - Acad. Press CY - San Diego, Calif. AN - OPUS4-1638 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kautek, Wolfgang A1 - Rudolph, Pascale A1 - Brzezinka, Klaus-Werner A1 - Wäsche, Rolf ED - Meunier, M. T1 - Physical chemistry of the femtosecond and nanosecond laser-material-interaction with SiC and a SiC-TiC-TiB2 composite ceramic compound N2 - The interaction of nanosecond laser pulses in the ultraviolet wavelength range and femtosecond laser pulses in the near-infrared region with the direct semiconductor SiC and the composite compound SiC-TiC-TiB2 was investigated in respect to resulting physicochemical processes. Surface analytical techniques, such as XPS, µ-Raman, and EDX were used to identify the chemical changes between untreated and laser-treated areas. Single-pulse irradiation led to material modifications in the condensed state in most instances. Multi-pulse results differed depending on the pulse duration. In the nanosecond case, melting of the surface and redeposited material (debris) were observed. With femtosecond pulses instead, only negligible melting and few debris could be detected. Additionally, periodic structures (ripples) appeared, with parallel orientation and in most cases two different periodicities for a particular material. Laser ablation of all the studied compound materials exhibited preferential ablation of the lighter component elements. Crystal structure changes of the irradiated surface were observed as a consequence of laser-induced melting and resolidification. An oxidation process interfered with all this processes so that unstoichiometric oxides were formed. T2 - Symposium D - European Materials Research Society CY - Strasbourg, France DA - 2002-06-18 PY - 2002 UR - http://www.emrs-strasbourg.com/files/pdf/2002_SPRING/02_Prog_Dv2.pdf N1 - Serientitel: Applied surface science – Series title: Applied surface science VL - 208/209.2003,1 IS - 1 SP - 1 PB - Elsevier CY - Amsterdam AN - OPUS4-1732 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Brzezinka, Klaus-Werner A1 - Schick, C. T1 - Behaviour of polymers confined to nanoporous glasses studied by dielectric, thermal and vibrational spectroscopy - Cut - off length scale for glass transition? T2 - Frühjahrstagung des Arbeitskreises Festkörperphysik bei der DPG CY - Regensburg, Germany DA - 2002-03-11 PY - 2002 SN - 0420-0195 SN - 0372-5448 SN - 0343-9216 IS - CPP 7.2 SP - 428 CY - Bad Honnef AN - OPUS4-2029 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Geißler, Heinz A1 - Peuker, Christel A1 - Brzezinka, Klaus-Werner A1 - Kohl, Anka A1 - Pilz, Walter T1 - OH- und H2O-Schwingungsbanden in den IR- und Raman-Spektren von Gläsern T2 - 74. Glastechnische Tagung CY - Ulm, Deutschland DA - 2000-05-29 KW - Raman-Spektren KW - IR-Spektren PY - 2000 SP - 164 EP - 167 PB - DGG, Dt. Glastechn. Ges. CY - Frankfurt/M. AN - OPUS4-889 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brzezinka, Klaus-Werner A1 - Gross, Thomas A1 - Unger, Wolfgang A1 - Ramm, M. A1 - Ata, M. T1 - Studies of amorphous carbon using X-ray photoelectron spectroscopy, near-edge X-ray-absorption fine structure and Raman spectroscopy KW - Amorphous materials KW - Carbon KW - Plasma processing and deposition KW - Structural properties PY - 1999 SN - 0040-6090 VL - 354 SP - 106 EP - 110 PB - Elsevier CY - Amsterdam AN - OPUS4-891 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Böhning, Martin A1 - Wald, Oliver A1 - Turky, Gamal A1 - Goering, Harald A1 - Brzezinka, Klaus-Werner A1 - Schartel, Bernhard A1 - Schönhals, Andreas T1 - Dielectric Relaxation and Gas Transport Properties in Polypropylene Based Nanocomposites T2 - ACS 2002 Biennial Symposium "Polymeric Nanomaterials" CY - Rohnert Park, CA, USA DA - 2002-11-17 PY - 2002 SP - 1(?) EP - 3(?) AN - OPUS4-2035 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Böhning, Martin A1 - Tidjani, Adams A1 - Wald, Oliver A1 - Turky, Gamal A1 - Goering, Harald A1 - Brzezinka, Klaus-Werner A1 - Schartel, Bernhard A1 - Schönhals, Andreas T1 - Polypropylene/Clay Nanocomposites - Gas Transport Characteristics and Molecular Mobility T2 - Polydays 2002 CY - Berlin, Germany DA - 2002-09-30 PY - 2002 SP - 1(?) EP - 2(?) AN - OPUS4-2038 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kautek, Wolfgang A1 - Pentzien, Simone A1 - Conradi, Andrea A1 - Krüger, Jörg A1 - Brzezinka, Klaus-Werner T1 - Pulsed-laser deposition and boron-blending of diamond-like carbon (DLC) thin films KW - Pulslaser KW - Bor KW - Dünnfilmtechnologie KW - Dünnfilm, diamantartig PY - 1996 SN - 0169-4332 SN - 1873-5584 VL - 106 SP - 158 EP - 165 PB - North-Holland CY - Amsterdam AN - OPUS4-630 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Böhning, Martin A1 - Goering, Harald A1 - Fritz, Andreas A1 - Brzezinka, Klaus-Werner A1 - Turky, Gamal A1 - Schönhals, Andreas A1 - Schartel, Bernhard T1 - Dielectric Study of Molecular Mobility in Poly(propylene-graft-maleic anhydride)/Clay Nanocomposites N2 - Polymer/clay nanocomposite materials based on poly(propylene-graft-maleic anhydride) (PPgMAH) and two different organophilic modified clays were investigated by dielectric relaxation spectroscopy (DRS). In contrast to ungrafted polypropylene (PP), PPgMAH shows a dielectrically active relaxation process which can be assigned to localized fluctuations of the polar maleic anhydride groups. Its relaxation rate exhibits an unusual temperature dependence, which could be attributed to a redistribution of water molecules in the polymeric matrix. This is confirmed by a combination of Raman spectroscopy and thermogravimetric experiments (TGA) with real-time dielectric measurements under controlled atmospheres. In the nanocomposites this relaxation process is shifted to higher frequencies up to 3 orders of magnitude compared to the unfilled polymer. This indicates a significantly enhanced molecular mobility in the interfacial regions. In the nanocomposite materials a separate high-temperature process due to Maxwell-Wagner-Sillars (MWS) polarization was observed. The time constant of this MWS process can be correlated with characteristic length scales in nanocomposites and therefore provides additional information on dispersion and delamination/exfoliation of clay platelets in these materials. These properties also influence the diffusivity of the water molecules as revealed by real-time dielectric investigations. KW - Polymer clay nanocomposites KW - Molecular mobility KW - Dielectric relaxation spectroscopy PY - 2005 DO - https://doi.org/10.1021/ma048315c SN - 0024-9297 SN - 1520-5835 VL - 38 IS - 7 SP - 2764 EP - 2774 PB - American Chemical Society CY - Washington, DC AN - OPUS4-7281 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Böhning, Martin A1 - Tidjani, Adams A1 - Wald, Oliver A1 - Brzezinka, Klaus-Werner A1 - Turky, Gamal A1 - Goering, Harald A1 - Schartel, Bernhard A1 - Schönhals, Andreas T1 - Dielectric and gas transport properties of polypropylene-clay nanocomposites T2 - Frühjahrstagung des Arbeitskreises Festkörperphysik bei der DPG CY - Regensburg, Germany DA - 2002-03-11 PY - 2002 SN - 0420-0195 SN - 0372-5448 SN - 0343-9216 IS - CPP 5.4 SP - 425 CY - Bad Honnef AN - OPUS4-2036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gaber, Martin A1 - Müller, Ralf A1 - Brzezinka, Klaus-Werner A1 - Peuker, Christel A1 - Langer, A. T1 - Analyse von Wasserstoff in Quarzglas T2 - 76. Glastechnische Tagung CY - Bad Soden, Deutschland DA - 2002-05-27 PY - 2002 SP - 242 EP - 245 PB - DGG, Deutsche Glastechnische Gesellschaft e.V. CY - Frankfurt/M. AN - OPUS4-1636 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Müller, Bernd R. A1 - Ekenhorst, Derk A1 - Brzezinka, Klaus-Werner A1 - Hentschel, Manfred P. ED - Krenkel, W. T1 - Fiber Induced Failure of Carbon/Carbon Composites T2 - 4th International Conference on High Temperature Ceramic Matrix Composites ; 4th HT-CMC Conference CY - Munich, Germany DA - 2001-10-01 PY - 2001 SN - 3-527-30320-0 VL - 4 SP - 175 EP - 180 PB - Wiley-VCH CY - Weinheim AN - OPUS4-1289 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -