TY - CONF A1 - Koudelka, L. A1 - Mosner, P. A1 - Zeyer, M. A1 - Jäger, Christian T1 - Structural study of PbO-B2O3-P2O5 glasses by NMR, Raman and infrared spectroscopy T2 - 19th International Congress on Glass CY - Edinburgh, Scotland, UK DA - 2001-07-01 PY - 2002 SN - 0-900682-39-6 N1 - Serientitel: Physics and chemistry of glasses – Series title: Physics and chemistry of glasses VL - 43C IS - 43C.2002 SP - 1 EP - 6 PB - Soc. of Glass Techn. CY - Sheffield AN - OPUS4-11012 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zeyer, M. A1 - Montagne, L. A1 - Kostoj, V. A1 - Palavit, G. A1 - Prochnow, D. A1 - Jäger, Christian T1 - 17O nuclear magnetic resonance study of Na2O-P2O5 glasses N2 - The preparation and structural investigation of 17O-enriched xNa2O–(100-x)P2O5 glasses (46.5<=x<=62.8) by nuclear magnetic resonance (NMR) is described. Enriched phosphoric acid was prepared by hydrolysis of PCl5 with 17O-enriched water and neutralized with sodium carbonate. The sodium metaphosphate was then melted at 800 °C for 15 h and quenched. Polyphosphate and ultraphosphate glass compositions were prepared by remelting the metaphosphate with sodium carbonate and phosphorus pentoxide, respectively. 31P magic angle sample spinning (MAS) NMR was used to determine the Na2O/P2O5 content in the glasses. 17O NMR spectra (quadrupole echo for non-rotating samples and multiple-quantum excitation for rotating samples (MQMAS)) show two oxygen sites in the samples with large quadrupolar coupling constants (4.7 and 7.7 MHz), in accordance with the high phosphorus electronegativity. According to the correlation of 17O quadrupolar constants with bond ionicity, these two components are attributed to bridging P–O–P and non-bridging P–O...Na oxygens. The average P–O–P bond angle is estimated with the quadrupolar asymmetry derived from the fit of the static echo spectra. The MQMAS spectrum shows a distribution of non-bridging oxygen chemical shifts, attributed to a variation of bond length and angle. PY - 2002 SN - 0022-3093 VL - 311 IS - 3 SP - 223 EP - 232 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-11013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Koudelka, L. A1 - Mosner, P. A1 - Zeyer, M. A1 - Jäger, Christian T1 - Structure and properties of mixed sodium-lead borophosphate glasses N2 - Mixed sodium–lead borophosphate glasses were prepared in two compositional series xNa2O–(50 - x)PbO–10B2O3–40P2O5 and xNa2O–(50 - x)PbO–20B2O3–30P2O5 with x = 0, 10, 20, 30, 40 and 50 mol% Na2O. Their density decreases and molar volume increases slightly with increasing Na2O content. Chemical durability decreases steeply for glasses containing 40–50 mol% Na2O, whereas glass transition temperatures reveals a minimum at the glasses with 30–40 mol% Na2O. The 31P MAS NMR and Raman spectra of the first series show that with increasing Na2O content the ratio of structural units Q2/Q1 slowly increases and the Q2 phosphate units and BO4 units prevail in the structure of these glasses. In the second series of glasses Q1 diphosphate units together with BO4 and small number of BO3 units form structural network of glasses. The replacement of PbO by Na2O results in higher ionicity of bonding interactions between compensating cations and the anionic network. The lower cation field strength of Na+ ions results in the observed downfield shift of ? (31P) values in Na-rich glasses and narrower vibrational bands in their Raman spectra. PY - 2005 DO - https://doi.org/10.1016/j.jnoncrysol.2005.01.015 SN - 0022-3093 VL - 351 IS - 12-13 SP - 1039 EP - 1045 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-11016 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zeyer, M. A1 - Montagne, L. A1 - Jäger, Christian T1 - Measuring oxygen-phosphorus distances and the orientation of electric field gradient tensors using 17O-{31P} REDOR in phosphate glasses N2 - Rotational echo double resonance (REDOR) of spin- nuclei is an extremely useful tool for the determination of distances in solids as well as of relative orientations of chemical shift and dipole tensors. We present the corresponding version for measuring the relative orientation of electric quadrupole and dipole tensors and demonstrate its applicability for non-bridging oxygens in phosphate glasses using 17O–{31P} REDOR NMR. The orientational information is found in the changes of the second-order quadrupole patterns as a function of the echo delay. Results and numeric simulations are presented for 17O–{31P} REDOR NMR of 17O-enriched sodium phosphate glasses. For non-bridging oxygens, the symmetric quadrupole tensor is found to be aligned along the phosphorus–oxygen bond. The distance between P and the non-bridging oxygen is calculated for two glasses of different compositions. KW - REDOR KW - Quadrupolar nuclei KW - O-17-{P-31} double resonance KW - Phosphate glasses PY - 2003 DO - https://doi.org/10.1016/S0926-2040(03)00012-2 SN - 0926-2040 SN - 1527-3326 VL - 23 IS - 3 SP - 136 EP - 144 PB - Academ. Press CY - Orlando, Fla. AN - OPUS4-11018 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Koudelka, L. A1 - Mosner, P. A1 - Zeyer, M. A1 - Jäger, Christian T1 - Lead borophosphate glasses doped with titanium dioxide N2 - Glasses of the compositional series of 50PbO–yB2O3–(50-y)P2O5–xTiO2 (with x=0–16) have been prepared and characterized by the determination of density, molar volume, glass transition temperature, dilatation softening temperature, thermal and chemical durability. Structural changes were evaluated from the studies by 31P and 11B MAS NMR, Raman and infrared spectroscopy. Molar volume of the glasses decreases and the glass transition temperature increases with increasing additions of TiO2. 31P MAS NMR spectra revealed that titanate units enter phosphate chains decreasing the number of Q2 units and increasing the number of Q1 units. This result is confirmed by the observed changes in the Raman and infrared spectra of the TiO2-doped glasses. PY - 2003 DO - https://doi.org/10.1016/S0022-3093(03)00380-6 SN - 0022-3093 VL - 326-327 SP - 72 EP - 76 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-11020 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Koudelka, L. A1 - Mosner, P. A1 - Petrík, J. A1 - Zeyer, M. A1 - Jäger, Christian T1 - Study of the structure of mixed lead borophosphate glasses by NMR, RAMAN and IR Spectroscopy PY - 2002 SN - 0918-4783 VL - 13 SP - 165 EP - 170 CY - Tokyo AN - OPUS4-11021 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zeyer, M. A1 - Montagne, L. A1 - Jäger, Christian A1 - Palavit, G. T1 - 17O NMR of Crystalline Sodium Trimetaphosphate PY - 2002 SN - 0918-4783 VL - 13 SP - 275 EP - 278 CY - Tokyo AN - OPUS4-11022 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Urmann, K. A1 - Schroth, M.H. A1 - Noll, Matthias A1 - Gonzalez-Gil, G. A1 - Zeyer, J. T1 - Assessment of microbial methane oxidation above a petroleum-contaminated aquifer using a combination of in situ techniques N2 - Emissions of the greenhouse gas CH4, which is often produced in contaminated aquifers, are reduced or eliminated by microbial CH4 oxidation in the overlying vadose zone. The aim of this field study was to estimate kinetic parameters and isotope fractionation factors for CH4 oxidation in situ in the vadose zone above a methanogenic aquifer in Studen, Switzerland, and to characterize the involved methanotrophic communities. To quantify kinetic parameters, several field tests, so-called gas push-pull tests (GPPTs), with CH4 injection concentrations ranging from 17 to 80 mL L-1 were performed. An apparent Vmax of 0.70 ± 0.15 mmol CH4 (L soil air)-1 h-1 and an apparent Km of 0.28 ± 0.09 mmol CH4 (L soil air)-1 was estimated for CH4 oxidation at 2.7 m depth, close to the groundwater table. At 1.1 m depth, Km (0.13 ± 0.02 mmol CH4 (L soil air)-1) was in a similar range, but Vmax (0.076 ± 0.006 mmol CH4 (L soil air)-1 h-1) was an order of magnitude lower. At 2.7 m, apparent first-order rate constants determined from a CH4 gas profile (1.9 h-1) and from a single GPPT (2.0 ± 0.03 h-1) were in good agreement. Above the groundwater table, a Vmax much higher than the in situ CH4 oxidation rate prior to GPPTs indicated a high buffer capacity for CH4. At both depths, known methanotrophic species affiliated with Methylosarcina and Methylocystis were detected by cloning and sequencing. Apparent stable carbon isotope fractionation factors a for CH4 oxidation determined during GPPTs ranged from 1.006 to 1.032. Variability was likely due to differences in methanotrophic activity and CH4 availability leading to different degrees of mass transfer limitation. This complicates the use of stable isotopes as an independent quantification method. KW - In situ quantification KW - Kinetics of microbial methane (CH4) oxidation KW - Stable isotope fractionation PY - 2008 DO - https://doi.org/10.1029/2006JG000363 SN - 0148-0227 VL - 113 SP - 02006-1-02006-11 PB - American Geophysical Union CY - Washington, DC AN - OPUS4-17332 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -