TY - JOUR A1 - Beck, Uwe A1 - Hübert, Thomas A1 - Kleinke, Helga T1 - Amorphous and nanocrystalline SrTiO3 thin films JF - Journal of non-crystalline solids KW - Schicht, dünn KW - Schicht, amorph KW - Schicht, nanokristallin KW - SrTiO3 PY - 1996 SN - 0022-3093 VL - 196 SP - 150 EP - 154 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-652 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Massiot, D. A1 - Müller, D. A1 - Hübert, Thomas A1 - Schneider, M. A1 - Kentgens, A. A1 - Coté, B. A1 - Coutures, J. A1 - Gessner, W. T1 - Double rotation and magic-angle spinning nuclear magnetic resonance study of 27Al: reexamination of the aluminium borate 9Al2O3 · 2B2O3 JF - Solid state nuclear magnetic resonance N2 - 27Al nuclear magnetic resonance spectra of polycrystalline aluminium borate 9Al2O3 · 2B2O3 have been measured in double rotation at 11.7 and 7.0 T and high-speed magic-angle spinning at 7.0, 9.4, 11.7, 14.1 and 17.6 T. Spinning sidebands from the satellite transitions were observed at 7.0 and 14.1 T. Each of the four structural aluminium sites [Al(IV), Al(V)(1), Al(V)(2) and Al(VI)] are observed, characterised and assigned in the spectra. The obtained parameter set gives a fully consistent interpretation in agreement with the crystal structure of the compound. KW - Aluminium KW - Kernresonanz, magnetisch KW - Winkel, magisch KW - Doppelrotation PY - 1995 DO - https://doi.org/10.1016/0926-2040(95)00021-H SN - 0926-2040 SN - 1527-3326 VL - 5 IS - 2 SP - 175 EP - 180 PB - Academ. Press CY - Orlando, Fla. AN - OPUS4-639 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas T1 - Humidity-Sensing Materials JF - MRS bulletin KW - Humidity-Sensing PY - 1999 DO - https://doi.org/10.1557/S0883769400052519 SN - 0883-7694 SN - 1938-1425 VL - 24 IS - 6 SP - 49 EP - 54 PB - Materials Research Society CY - Pittsburgh, Pa. AN - OPUS4-810 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mosel, Günter A1 - Willfahrt, Manfred A1 - Banach, Ulrich A1 - Hübert, Thomas T1 - An extended X-ray absorption fine structure investigation on the local environment of niobium ions in Nb2O5-doped SrTiO3 glass ceramics JF - Journal of materials science PY - 1997 SN - 0022-2461 SN - 1573-4803 VL - 32 SP - 1591 EP - 1597 PB - Springer Science + Business Media B.V. CY - Norwell, Mass. AN - OPUS4-2045 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Schuffenhauer, W. A1 - Wernecke, R. T1 - Selbstüberwachendes und -regenerierendes System zur Online-Spurenfeuchtemessung in chemischen Prozessgasen JF - Chemie - Ingenieur - Technik PY - 2000 DO - https://doi.org/10.1002/1522-2640(200011)72:11<1376::AID-CITE1376>3.0.CO;2-C SN - 0009-286X SN - 1522-2640 VL - 72 IS - 11 SP - 1380 EP - 1382 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-2048 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Mosel, Günter A1 - Witke, Klaus T1 - Structural Elements in Borovanadate Glasses JF - Glass physics and chemistry N2 - The structure of glasses in the Li2O–B2O3–V2O5and ZnO–B2O3–V2O5systems of a high modifier content ([Li2O, ZnO]/[B2O3] ratio > 1) and 10 to 50 mol % V2O5are investigated by V-KEXAFS and Raman spectroscopy. In the glasses investigated, VO4tetrahedra are the predominant coordination polyhedra for the vanadium ions. The symmetry of the tetrahedra is more or less distorted in comparison with crystalline substances. The VO4tetrahedra can be either directly connected to each other or incorporated into the borate groupings of the BO3and BO4units. An increase in the vanadium content in the glasses reduces the interconnection of structural units and, therefore, the glass transition and crystallization temperatures. T2 - International Conference "Thermodynamics and Chemical Structure of melts and Glasses" CY - St. Petersburg, Russia DA - 1999-09-07 PY - 2001 DO - https://doi.org/10.1023/A:1011376225695 SN - 1087-6596 SN - 1608-313X VL - 27 IS - 2 SP - 114 EP - 120 PB - Pleiades Publ. CY - New York, NY AN - OPUS4-2049 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Polyakova, Irina A1 - Hübert, Thomas T1 - Thermal stability of TiN thin films investigated by DTG/DTA JF - Surface and coatings technology N2 - The paper demonstrates the scope of the differential thermal analysis coupled with the thermal gravimetry as an express method for estimation of thin film protecting ability and oxidation kinetics. Oxidation of an iron foil protected by the PVD titanium nitride thin film coating was investigated as well as non-isothermal oxidation of PVD thin films of TiN (two types of the preparation procedure), (Ti,Nb)N and (Ti,Al)N isolated from a substrate by dissolving them in an acid. Additions of aluminium and niobium are expected to improve chemical, thermal and biomedical properties of thin films for their technical application. It was established that the addition of niobium decreases, whereas the addition of aluminium not only increases the thermal stability of TiN coatings, but also changes the oxidation mechanism. It was demonstrated that the TiN film oxidation is a many-staged process depending on the heating rate. An opportunity of a quite formal treatment for getting Kissinger's estimation of kinetics parameters of different oxidation stages is also demonstrated. PY - 2001 DO - https://doi.org/10.1016/S0257-8972(01)01042-8 SN - 0257-8972 VL - 141 IS - 1 SP - 55 EP - 61 PB - Elsevier Science CY - Lausanne AN - OPUS4-2050 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Willfahrt, Manfred A1 - Witke, Klaus A1 - Reich, Peter T1 - Low Frequency Raman Investigations of Lead Borate and Lead Alumino Borate Glasses JF - Journal of molecular structure PY - 1995 SN - 0022-2860 SN - 1872-8014 SN - 0377-046X VL - 349 SP - 373 EP - 376 PB - Elsevier CY - Amsterdam AN - OPUS4-3776 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Schuffenhauer, W. A1 - Wernecke, R. T1 - Self-Monitoring and Self-Regenerating System for On-line Measuring of Moisture Traces in Chemical Process Gases JF - Chemical engineering & technology PY - 2002 DO - https://doi.org/10.1002/1521-4125(200205)25:5<492::AID-CEAT492>3.0.CO;2-L SN - 0930-7516 SN - 1521-4125 VL - 25 IS - 5 SP - 492 EP - 494 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-3777 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Schwarz, J. A1 - Oertel, B. T1 - Sol-gel alumina coatings on stainless steel for wear protection JF - Journal of sol gel science and technology N2 - The aluminium oxide films on austenitic steel are prepared from sols of re-dispersed boehmite nano powders in water. After dip-coating of the sol, a heat treatment including drying, calcination and annealing in vacuum at temperatures up to 1100°C is performed to obtain crack-free coatings of a thickness up to 6 µm. XRD measurements detect α- and γ-alumina, a TiOx-phase at the metal/coating interface and a gradient of phase formation in the coating. The strong adhesion on the substrates is due to the layered assembly and gradient composition of the coating caused by an inter-diffusion of metal cations and oxygen in the metal/oxide interface during heat treatment. Residual stress measurements by X-rays result in compressive stresses of 2–4 GPa in the alumina coatings. The pin-on-disc test shows a remarkable improvement of wear resistance obtained by sol-gel coatings. The α-alumina content and the compressive stress of the coatings correlate with wear resistance of the coatings. KW - Alumina KW - Sol-gel KW - Coating KW - Wear protection KW - Residual stress PY - 2006 DO - https://doi.org/10.1007/s10971-006-6470-7 SN - 0928-0707 SN - 1573-4846 VL - 38 IS - 2 SP - 179 EP - 184 PB - Kluwer Academic Publ. CY - Dordrecht AN - OPUS4-12435 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Bauroth, F. A1 - Oertel, B. A1 - Svoboda, S. T1 - Aluminiumoxid-Sol/Gel-Schutzschichten auf Metallen JF - Ceramic Forum International : cfi PY - 1995 SN - 0173-9913 SN - 0196-6219 VL - 10 IS - 4 SP - 60 EP - 66 PB - Göller CY - Baden-Baden AN - OPUS4-5680 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lippitz, Andreas A1 - Hübert, Thomas T1 - XPS investigations of chromium nitride thin films JF - Surface and coatings technology N2 - Cr–N film coatings were prepared by magnetron sputter deposition at different nitrogen partial pressures. The film characterisation by XRD and DTG gives average bulk compositions of Cr2N and CrN for the coatings. Highly sensitive XPS investigations were performed and the chemical and phase compositions of a film surface range of about 10 nm thickness was estimated quantitatively from the deconvoluted peak intensities. It is demonstrated that the composition of the surface of chromium nitride thin films differs from the core and is more complex in constitution. Not only chromium nitrides (Cr2N and CrN) but also chromium oxynitrides and chromium oxides (CrOx and CrOxHy) were detected. Metallic chromium was also found in films prepared at higher nitrogen flow. The concentration of the estimated phases shows dependence on film preparation and additional heat treatment. KW - XPS KW - ESCA KW - Physical vapour deposition (PVD) KW - CrN thin films PY - 2005 DO - https://doi.org/10.1016/j.surfcoat.2005.02.091 SN - 0257-8972 VL - 200 IS - 1-4 SP - 250 EP - 253 PB - Elsevier Science CY - Lausanne AN - OPUS4-10865 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gerlitzke, A.-K. A1 - Nörthemann, K. A1 - Lang, M. A1 - Milstrey, M. A1 - Kaufer, R. A1 - Woratz, M. A1 - Banach, Ulrich A1 - Hübert, Thomas A1 - Moritz, W. T1 - Long-term stability of the low energy hydrogen sensor T2 - IMCS 2012 - 14th International meeting on chemical sensors N2 - A silicon MIS-structure prepared with thin layers of the super-ionic conductor LaF3 and Pd is used to detect hydrogen. The sensor is able to detect hydrogen in a concentration range from below one ppm to the lower flammable limit in air which is 4 vol.-%. The chip operates at room temperature which results in an extremely low energy consumption compared to other hydrogen sensors. Only once per day a short heating pulse is necessary to reactivate the sensor chip. In cooperation with the BAM, a long-term experiment was carried out. The duration of the measurement was about three months, with a hydrogen exposure every two weeks. The sensor signal remained stable over the measured period. T2 - IMCS 2012 - 14th International meeting on chemical sensors CY - Nuremberg, Germany DA - 20.05.2012 KW - Hydrogen detection KW - Long-term measurement KW - MIS-structure KW - Low energy sensor PY - 2012 SN - 978-3-9813484-2-2 DO - https://doi.org/10.5162/IMCS2012/P2.5.1 SP - 1571 EP - 1574 PB - AMA Service GmbH CY - Wunstorf AN - OPUS4-26177 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tiebe, Carlo A1 - Hübert, Thomas A1 - Lorek, A. A1 - Wernecke, R. T1 - New planar trace humidity sensor T2 - IMCS 2012 - 14th International meeting on chemical sensors N2 - A new planar sensor element for continuous coulometric trace humidity measurements in industrial gases has been developed. In order to ensure precise measurements a calibration facility including a precision dew point hygrometer as a reference device was developed. The sensor can measure the humidity in the frost point temperature range of -20 °C to -80 °C and has an expanded uncertainty of 2 K, a fast reaction time and a settling time of the entire system from 15 to 30 min. T2 - IMCS 2012 - 14th International meeting on chemical sensors CY - Nuremberg, Germany DA - 2012-05-20 KW - Trace humidity KW - Coulometric principle KW - HUMITRACE sensor KW - Humidity measurement PY - 2012 SN - 978-3-9813484-2-2 DO - https://doi.org/10.5162/IMCS2012/3.4.2 SP - 294 EP - 297 PB - AMA Service GmbH CY - Wunstorf AN - OPUS4-27570 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nie, Yaru A1 - Hübert, Thomas T1 - Effect of carbon nanofiber (CNF) silanization on the properties of CNF/epoxy nanocomposites JF - Polymer International N2 - Carbon nanofibers (CNFs) were functionalized by a multistage process including oxidation, reduction and silanization. The chemical modifications were examined by Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry, Raman spectroscopy and thermogravimetric analysis. The silanized CNFs were then added into an epoxy resin (EPON 828) to study the effect of the surface modification of CNFs on the properties of nanocomposites. For comparison, nanocomposites containing original unmodified CNFs were also investigated. Scanning electron microscopy indicates better dispersion of modified fibers in the epoxy polymer matrix; the mechanical and thermal properties of composites are also improved; the electrical conductivity of the composites is reduced. KW - Carbon nanofibers KW - Epoxy composites KW - Silanization KW - Electrical conductivity KW - Thermal conductivity KW - Mechanical properties PY - 2011 DO - https://doi.org/10.1002/pi.3124 SN - 0959-8103 SN - 1097-0126 SN - 0007-1641 VL - 60 IS - 11 SP - 1574 EP - 1580 PB - Wiley InterScience CY - Chichester, West Sussex AN - OPUS4-25865 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Brita A1 - Bücker, Michael A1 - Reinsch, Stefan A1 - Hübert, Thomas T1 - Chemical aspects of wood modification by sol-gel-derived silica JF - Wood science and technology N2 - It has been shown that tetraethoxysilane-derived precursors are suitable solutions for impregnating pine sapwood to improve its dimensional stability. Tailored sol–gel syntheses result in precursors with nano-scaled silica species which are able to penetrate into the cell walls of wood. The physical fixation of those species inside the cell walls was verified by ESEM/EDX investigations. There is evidence that the silica species are chemically bonded to wood components. Nonreacted alkoxy groups can exist in the wood composites after impregnation. The amount of these organic residues depends on the composition of the precursors, especially their condensation degree and reactivity. Treatments for finishing the composites after the impregnation step to get clean products and stable properties are discussed in this context. An explanation of the complex relationship between solids content in the impregnation solutions and percentage weight gain and bulking of the composites is given. It can be demonstrated that high WPG values (>20 %) are pre-conditions for an effective protection of the resulting composites but they only guarantee efficient improvements if connected with the incorporation of the inorganic component inside the cell walls. Therefore, the sol–gel syntheses have to be carried out in such a manner that very small (<2 nm) as well as reactive species are sufficiently available. This demands syntheses using sub-stoichiometric water contents (H2O/TEOS <4, better <2). KW - Silica-wood composites KW - Sol-gel derived precursors KW - Curing KW - Fixation of silica KW - Dimensional stability PY - 2013 DO - https://doi.org/10.1007/s00226-012-0486-7 SN - 0043-7719 SN - 1432-5225 VL - 47 IS - 1 SP - 83 EP - 104 PB - Springer CY - Berlin AN - OPUS4-26258 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shimamura, Aki A1 - Hübert, Thomas A1 - Thust, H. T1 - Characterization of sol-gel derived glass composite thin films JF - Surface and interface analysis N2 - A comprehensive analysis of composition and structure is essential for the development of new materials with tailored properties. We will demonstrate the application of SEM, XPS and XRD for the development of thin films containing nano-scaled electrical conductive particles for application in hybrid resistors. The films were prepared using the sol-gel process and precursor solutions were synthesized from an acid hydrolysis of a mixture of TEOS, water and ethanol. Alcoholic solutions of ruthenium chloride were then allocated to obtain up to 30 vol% filler in the films. The films were precipitated by dip-coating on silicon, silica or glass sheets and heat treated at up to 600°C in air or nitrogen atmospheres. A nano-structured morphology could be identified consisting of homogeneously dispersed crystalline RuO2 particles of 10 to 180 nm in size, in an amorphous SiO2 matrix. Film morphology can be varied using the synthesis process. The resistivity of the films was measured by an I-V measurement system. It changes drastically from 109·cm to 10-2·cm according to the amount of dispersed conductive particles. The results show that composition-structure-property relations can be described by use of sophisticated analytical methods. T2 - 10th European Conference on Applications of Surface and Interface Analysis (ECASIA '03) CY - Berlin, Germany DA - 2003-10-05 KW - Sol-gel KW - Thin film KW - Nano-structure KW - Electrical resistivity KW - RuO2 PY - 2004 DO - https://doi.org/10.1002/sia.1877 SN - 0142-2421 SN - 1096-9918 VL - 36 IS - 8 SP - 1207 EP - 1209 PB - Wiley CY - Chichester AN - OPUS4-4753 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Shimamura, Aki A1 - Klyszcz, Andreas T1 - Electrical Properties of Carbon Black and Ruthenium Dioxide Embedded Silica Films JF - Journal of sol gel science and technology N2 - The electrical properties of sol–gel-derived films can be tailored by embedding conductive particles of ruthenium dioxide or carbon black in an insulating amorphous SiO2 silica matrix. The preparation process included an acid hydrolysis of tetraethoxysilane and methyltrimethoxysilane. Then alcohol solutions of ruthenium chloride or carbon black were added. Films of filler concentration up to 60 vol.% were prepared by dip coating and then dried and heat-treated at various temperatures up to 600_°C. The D.C. resistance of the films can be varied within the range of 109 to 10–2 OHgr sdot cm. A non-linear dependence on filler composition in the films was observed for both systems, which is explained by a modified percolation theory. A percolation threshold of 5.5 vol.% for SiO2-RuO2 or 50 vol.% for SiO2-C films, whereby the resistance drastically decreases, was determined. Moreover the temperature dependency of resistance and the current-voltage characteristics of the films can also be explained by this geometric model. KW - Sol-gel KW - Thin films KW - Carbon black KW - Ruthenium dioxide KW - Percolation phenomena PY - 2004 DO - https://doi.org/10.1007/s10971-004-5777-5 SN - 0928-0707 SN - 1573-4846 VL - 32 SP - 131 EP - 135 PB - Kluwer Academic Publ. CY - Dordrecht AN - OPUS4-6909 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Shimamura, Aki A1 - Klyszcz, Andreas T1 - Carbon-silica sol-gel derived nanomaterials JF - Materials science : international journal N2 - The preparation of sol-gel derived silica-based nanomaterials containing electrical conductive carbon fillers in an extensive composition range is described and their electrical properties are presented. Nanomaterials of carbon filler concentrations up to 60% (v/v) were obtained by dip coating or screen-printing from precursors of hydrolysed alkoxysilanes. Nanostructured morphology could be identified to consist of homogeneously dispersed carbon black particles or carbon fibres of 30 to 500 nm in size in a modified silica matrix. The electrical resistivity of the films changes drastically from 1010 to 10?1 O?cm, according to the amount of dispersed conductive particles. A threshold between 5 and 50% (v/v), at which the resistance abruptly decreases, was determined. A geometrical model related to percolation theory explains this non-linear dependence on the filler composition in the materials. Moreover the temperature dependence of resistance and the current-voltage characteristics of the nanomaterials can also be illustrated using this geometric model. KW - Sol-gel KW - Nanomaterials KW - Carbon black KW - Electrical resitivity KW - Percolation PY - 2005 UR - http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.123.3004&rep=rep1&type=pdf SN - 0137-1339 VL - 23 IS - 1 SP - 61 EP - 68 PB - Technical Univ. Press CY - Wroclaw AN - OPUS4-7362 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübert, Thomas A1 - Svoboda, S. A1 - Oertel, B. T1 - Wear resistant alumina coatings produced by a sol-gel process JF - Surface and coatings technology N2 - Aluminium oxide films were prepared by a dip-coating procedure from solutions of hydrolysed aluminium-tri-sec-butoxide in methoxyethanol on austenitic steel as well as hard metal tools. The heat treatment was performed in an argon atmosphere or vacuum at temperatures up to 1100 °C. Characterisation of the coatings by SEM, showed nearly crack free coatings with a dense morphology which completely cover the substrate. The chemical composition of the coatings was investigated by ESCA, GD-OES and XRD measurements. This analysis detected a multi-layered arrangement of spinel phases, ?- and ?-alumina in the coatings. The scratch test showed sufficient adhesion of the coatings comparable to CVD layers. Pin-on-disc and oscillating sliding tests were carried out on sol–gel coated samples and also on uncovered reference samples. The determined wear rates and friction coefficients showed significant improvement in wear resistance of sol–gel coatings containing a corundum phase. The strong adhesion to the substrates is due to a layered assembly formation and gradient composition of the coating caused by an interdiffusion of metal cations and oxygen in the metal/oxide interface during heat treatment. KW - Oxide film formation KW - Film analysis KW - Wear resistance PY - 2006 DO - https://doi.org/10.1016/j.surfcoat.2005.11.014 SN - 0257-8972 VL - 201 IS - 1-2 SP - 487 EP - 491 PB - Elsevier Science CY - Lausanne AN - OPUS4-18583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -