TY - JOUR A1 - Nguyen, V. H. A1 - Ren, Y. A1 - Lee, Y. R. A1 - Tuma, Dirk A1 - Min, B.-K. A1 - Shim, J.-J. T1 - Microwave-assisted synthesis of carbon nanotube-TiO2 nanocomposites in ionic liquid for the photocatalytic degradation of methylene blue N2 - A simple and efficient method of preparing composites of carbon nanotubes and titania (CNT-TiO2) is reported via a microwave-assisted synthesis in an ionic liquid, [bmim][BF4]. CNT-TiO2 nanocomposites were formed by the thermal decomposition of titanium (IV) isopropoxide (Ti(OPri)4) in the presence of CNTs under microwave irradiation. The obtained product was characterized by BET surface area, XRD, SEM, and TEM. TiO2 particles with average size of 9 nm were as anatase. The surface area of the Composites increased with an increase of CNT content. Moreover, the catalytic efficiency of the composite was investigated through the photoelectrodegradation of methylene blue. KW - Carbon nanotube KW - Ionic liquid KW - Microwave KW - Photocatalyst KW - TiO2 nanoparticles PY - 2012 DO - https://doi.org/10.1080/15533174.2011.610021 SN - 1553-3174 SN - 1553-3182 VL - 42 IS - 2 SP - 296 EP - 301 PB - Taylor and Francis Group, LLC CY - London AN - OPUS4-35895 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hernández-Gómez, R. A1 - Tuma, Dirk A1 - Lozano-Martín, D. A1 - Chamorro, C. R. T1 - Accurate experimental (p, rho, T) data of natural gas mixtures for the assessment of reference equations of state when dealing with hydrogen-enriched natural gas N2 - The GERG-2008 equation of state is the approved ISO standard (ISO 20765-2) for the calculation of thermophysical properties of natural gas mixtures. The composition of natural gas can vary considerably due to the diversity of origin. Further diversification was generated by adding hydrogen, biogas, or other non-conventional energy gases. In this work, high-precision experimental (p, rho, T) data for two gravimetrically prepared synthetic natural gas mixtures are reported. One mixture resembled a conventional natural gas of 11 components (11 M) with a nominal mixture composition (amount-of-substance fraction) of 0.8845 for methane as the matrix compound with the other compounds being 0.005 for oxygen, 0.04 for nitrogen, 0.015 for carbon dioxide, 0.04 for ethane, 0.01 for propane, 0.002 each for n- and isobutane, and ultimately 0.0005 each for isopentane, n-pentane, and nhexane. The other mixture was a 13-component hydrogen-enriched natural gas with a low calorific value featuring a nominal composition of 0.7885 for methane, 0.03 for hydrogen, 0.005 for helium, 0.12 for nitrogen, 0.04 for carbon dioxide, 0.0075 for ethane, 0.003 for propane, 0.002 each for n- and isobutane, and 0.0005 each for neopentane, isopentane, npentane, and n-hexane. Density measurements were performed in an isothermal operational mode at temperatures between 260 and 350 K and at pressures up to 20 MPa by using a single-sinker densimeter with magnetic suspension coupling. The data were compared with the corresponding densities calculated from both GERG-2008 and AGA8-DC92 equations of state to test their performance on real mixtures. The average absolute Deviation from GERG-2008 (AGA8-DC92) is 0.027% (0.078%) for 11 M and 0.095% (0.062%) for the 13-component H2-enriched mixture, respectively. The corresponding maximum relative Deviation from GERG-2008 (AGA8-DC92) amounts to 0.095% (0.127%) for 11 M and 0.291% (0.193%) for the H2-enriched mixture. KW - Hydrogen-enriched natural gas KW - Gravimetric preparation KW - Volumetric data KW - GERG-2008 equation of state PY - 2018 DO - https://doi.org/10.1016/j.ijhydene.2018.10.027 SN - 0360-3199 SN - 1879-3487 VL - 43 IS - 49 SP - 21983 EP - 21998 PB - Elsevier CY - Amsterdam AN - OPUS4-46686 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tuma, Dirk T1 - High-pressure density data of hydrogen-containing natural gases for the extension of equation-of-state models N2 - This presentation reports new density data of hydrogen-containing natural gas mixtures between 250 and 350 K and up to pressures of 20 MPa. T2 - 11th International GAS Analysis Symposium & Exhibition CY - Paris, France DA - 17.05.2022 KW - Hydrogen-containing natural gas KW - Density data KW - Equation of state PY - 2022 AN - OPUS4-56433 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - van der Veen, A. M H A1 - Zalewska, E. T. A1 - Kipphardt, Heinrich A1 - Beelen, R. R. A1 - Tuma, Dirk A1 - Maiwald, Michael A1 - Fükő, J. A1 - Büki, T. A1 - Szilágyi, Z. N. A1 - Beránek, J. A1 - Cieciora, D. A1 - Ochman, G. A1 - e.t al., T1 - Metrologia International Bureau of Weights and Measures (BIPM), find out more - KEY COMPARISON International comparison CCQM-K118 natural gas N2 - CCQM-K118 was an international key comparison on natural gas composition with two types of gases, i.e., a low calorific hydrogen-enriched natural gas and a high calorific LNG type of gas. There were 14 participating laboratories. The traveling standards (i.e., 14 mixtures each) were obtained from an external source and checked for homogeneity and stability before and after the participants' measurements at the two coordinating laboratories. The data evaluation was performed using a consensus value and a laboratory effect model. The results of the participants were benchmarked against a key comparison reference value computed from the largest consistent subset (LCS) of the submitted results, adjusted for the differences between the travelling standards. For the first time in a key comparison in gas analysis, the model included a term to account for excess variability in the LCS. Most of the participants reported one or a few (slightly) discrepant results. Partly this is due to the heterogeneity and heteroscedasticity of the datasets. In all, the results in this key comparison demonstrate the good comparability of the national measurement standards for natural gas composition maintained by the participating NMIs. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA). To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA). KW - CCQM-K PY - 2022 DO - https://doi.org/10.1088/0026-1394/59/1A/08017 SN - 0026-1394 VL - 59 IS - 1A PB - IOP Publishing LTD AN - OPUS4-56308 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lozano-Martín, D. A1 - Martín, M. C. A1 - Chamorro, C. R. A1 - Tuma, Dirk A1 - Segovia, J. J. T1 - Speed of sound for three binary (CH4 + H2) mixtures from p = (0.5 up to 20) MPa at T = (273.16 to 375) K N2 - Speed of sound is one of the thermodynamic properties that can be measured with least uncertainty and is of great interest in developing equations of state. Moreover, accurate models are needed by the H2 industry to design the transport and storage stages of hydrogen blends in the natural gas network. This research aims to provide accurate data for (CH4 + H2) mixtures of nominal (5, 10, and 50) mol-% of hydrogen, in the p = (0.5 up to 20) MPa pressure range and with temperatures T = (273.16, 300, 325, 350, and 375) K. Using an acoustic spherical resonator, speed of sound was determined with an overall relative expanded (k = 2) uncertainty of 220 parts in 10^6 (0.022%). Data were compared to reference equations of state for natural gas-like mixtures, such as AGA8-DC92 and GERG-2008. Average absolute deviations below 0.095% and percentage deviations between 0.029% and up to 0.30%, respectively, were obtained. Additionally, results were fitted to the acoustic virial equation of state and adiabatic coefficients, molar isochoric heat capacities and molar isobaric heat capacities as perfect-gas, together with second and third acoustic virial coefficients were estimated. Density second virial coefficients were also obtained. KW - Speed of sound KW - Acoustic resonator KW - Heat capacity PY - 2020 DO - https://doi.org/10.1016/j.ijhydene.2019.12.012 SN - 0360-3199 VL - 45 IS - 7 SP - 4765 EP - 4783 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-50454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lozano-Martín, D. A1 - Akubue, G. U. A1 - Moreau, A. A1 - Tuma, Dirk A1 - Chamorro, C. R. T1 - Accurate experimental (p, rho, T) data of the (CO2 + O2) binary system for the development of models for CCS processes N2 - The limited availability of accurate experimental data in wide ranges of pressure, temperature, and composition is the main constraining factor for the proper development and assessment of thermodynamic models and equations of state. In the particular case of carbon capture and storage (CCS) processes, there is a clear need for data sets related to the (carbon dioxide + oxygen) mixtures that this work aims to address. This work provides new experimental (p, rho, T) data for three binary (CO2 + O2) mixtures with mole fractions of oxygen x(O2) = (0.05, 0.10, and 0.20) mol/mol, in the temperature range T = (250 to 375) K and pressure range p = (0.5 to 13) MPa. The measurements were performed with a high-precision single-sinker densimeter with magnetic suspension coupling. The density data were obtained with estimated expanded relative uncertainties of 0.02 % for the highest densities and up to 0.3 % for the lowest ones.The results were compared to the corresponding results calculated by the current reference equations of state for this kind of mixtures, namely the EOS-CG (combustion gases) and the GERG-2008 equation of state, respectively. The EOS-CG yields better estimations in density than the GERG-2008 equation of state. The results from the EOS-GC model show no systematic temperature dependence. For the GERG-2008 model, however, this criterion is significantly less fulfilled. KW - carbon capture and storage KW - single-sinker densimeter KW - equation of state PY - 2020 DO - https://doi.org/10.1016/j.jct.2020.106210 SN - 0021-9614 VL - 150 SP - 106210 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-50925 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tuma, Dirk A1 - Lozano-Martín, D. A1 - Vega-Maza, D. A1 - Moreau, A. A1 - Martín, M. C. A1 - Segovia, J. J. T1 - Speed of sound data, derived perfect-gas heat capacities, and acoustic virial coefficients of a calibration standard natural gas mixture and a low-calorific H2-enriched mixture N2 - This work aims to address the technical aspects related to the thermodynamic characterization of natural gas mixtures blended with hydrogen for the introduction of alternative energy sources within the Power-to-Gas framework. For that purpose, new experimental speed of sound data are presented in the pressure range between (0.1 up to 13) MPa and at temperatures of (260, 273.16, 300, 325, and 350) K for two mixtures qualified as primary calibration standards: a 11 component synthetic natural gas mixture (11 M), and another low-calorific H2-enriched natural gas mixture with a nominal molar percentage x(H2) = 3 %. Measurements have been gathered using a spherical acoustic resonator with an experimental expanded (k = 2) uncertainty better than 200 parts in 106 (0.02 %) in the speed of sound. The heat capacity ratio as perfect-gas gammapg, the molar heat capacity as perfect-gas Cp,m pg, and the second betaa and third gammaa acoustic virial coefficients are derived from the speed of sound values. All the results are compared with the reference mixture models for natural gas-like mixtures, the AGA8-DC92 EoS and the GERG-2008 EoS, with Special attention to the impact of hydrogen on those properties. Data are found to be mostly consistent within the model uncertainty in the 11 M synthetic mixture as expected, but for the hydrogen-enriched mixture in the limit of the model uncertainty at the highest measuring pressures. KW - Natural gas mixtures KW - Speed-of-sound measurements KW - Equations of state KW - Acoustic virial coefficients PY - 2021 DO - https://doi.org/10.1016/j.jct.2021.106434 SN - 0021-9614 VL - 158 SP - 106434 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-52292 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lamiel, C. A1 - Nguyen, V. H. A1 - Tuma, Dirk A1 - Shim, J.-J. T1 - Non-aqueous synthesis of ultrasmall NiO nanoparticle-intercalated graphene composite as active electrode material for supercapacitors N2 - With the vast exploration of the applications of graphene, researchers are assessing different methods for fabricating graphene-based electrode material with high capacitance but low material and energy costs. In this study, reduced graphene oxide/nickel oxide (RGO/NiO) nanocomposites were prepared using a non-aqueous solvent-based method followed by calcination. Nickel acetate tetrahydrate and tert-butanol were used as the precursor and solvent, respectively. Ultrasmall nickel oxide nanoparticles, ca. 8.0 nm in size, were deposited on the surface of the graphene sheets simultaneously with the partial reduction of graphene oxide. The resulting RGO/NiO electrode exhibited a high capacitance of 689 F g⁻1 at a current density of 0.8 A g⁻1. After 1500 cycles, the specific retention and the coulombic efficiency yielded to 86.34% and 96.39%, respectively, which supports the viability of this composite as an alternative activated material with high electrochemical performance. KW - Nanocomposite KW - Graphene KW - Supercapacitor PY - 2016 DO - https://doi.org/10.1016/j.materresbull.2016.06.005 SN - 0025-5408 SN - 1873-4227 VL - 83 SP - 275 EP - 283 PB - Elsevier Ltd. CY - London AN - OPUS4-36812 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tuma, Dirk T1 - Thermophysical properties of hydrogen-containing mixtures for the extension of equation-of-state models for natural gas N2 - The decarbonization of the energy sector is driving the interest in hydrogen as an energy-storage medium. A practical alternative to transport and distribute H2 is using the existing infrastructure for natural gas. The GERG-2008 equation of state currently serves as the ISO standard (ISO 20765-2) for the calculation of thermodynamic properties of natural gas, but H2 appears only as a secondary component. The availability of consolidated data for mixtures with H2 available at the time of its constitution was very limited. The experimental characterization of the thermodynamic behavior of mixtures of H2 with the main components of natural gas is thus of great relevance to validate and improve the GERG-2008 equation of state for its use with H2-enriched natural gas. T2 - Thermodynamik-Kolloquium 2021 CY - Online meeting DA - 27.09.2021 KW - Hydrogen-containing mixtures KW - Density measurements KW - Equations of state PY - 2021 AN - OPUS4-53991 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhou, Z. A1 - Han, Q. A1 - Wang, D. A1 - Macé, T. A1 - Kipphardt, Heinrich A1 - Maiwald, Michael A1 - Tuma, Dirk A1 - Uehara, S. A1 - Akima, D. A1 - Shimosaka, T. A1 - Jung, J. A1 - Oh, S.-H. A1 - van der Veen, A. A1 - van Wijk, J.I.T. A1 - Ziel, P. R. A1 - Konopelko, L. A1 - Valkova, M. A1 - Mogale, D.M. A1 - Botha, A. A1 - Brewer, P. A1 - Murugan, A. A1 - Minnaro, M.D. A1 - Miller, M. A1 - Guenther, F. A1 - Kelly, M.E. T1 - CCQM K101 Final report international comparison CCQM-K101:Oxygen in nitrogen-a track B comparison and that the matrix contains argon N2 - This key comparison aims to assess the capabilities of the participants to determine the amount-of-substance fraction oxygen in nitrogen. The GAWG has classified this as a track B comparison, due to the unexpected 50 μmol/mol argon mole fraction content of the transfer standards, which effects the achievable performance of some measurement techniques such a GC-TCD. The separation of oxygen and argon is challenging, and not all systems in use are equally well designed for it. As this analytical challenge due to a substantial fraction of argon in the transfer standards became a reality, the Gas Analysis Working Group (GAWG) decided to qualify this key comparison as a regular key comparison and not as a core comparison, which may be used to support calibration and measurement capabilities (CMCs) for oxygen in nitrogen, or for oxygen in nitrogen mixtures containing argon only (see also the section on support to CMCs). KW - CCQM-K101 KW - Gas analysis PY - 2016 UR - http://iopscience.iop.org/article/10.1088/0026-1394/53/1A/08013 SN - 1681-7575 SN - 0026-1394 VL - 53 IS - Techn Suppl SP - 08013, 1 EP - 71 PB - IOP publishing AN - OPUS4-40013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Culleton, L.P. A1 - Brown, A. A1 - Murugan, A. A1 - Van der Veen, A. A1 - Van Osselen, D. A1 - Ziel, P. R. A1 - Li, J. A1 - Tuma, Dirk A1 - Schulz, Gert A1 - Näther, Stephanie A1 - Arrhenius, K. A1 - Kühnemuth, D. A1 - Beránek, J. A1 - Fuko, J. A1 - Val'ková, M. T1 - Results of an international comparison on the analysis of real nonconventional energy gases N2 - The requirement for a metrological infrastructure to ensure the interchangability of 'nonconventional’ energy gases within existing European infrastructure1 was the driving force behind the work undertaken in the three-year EMRP Characterisation of energy gases project EMRP ENG01 (June 2010 - May 2013). As part of work package one of the project, Standards and methods were used to perform composition and impurity measurements on samples of real energy gases collected from around Europe. The aim of this study was to compare the results obtained from different labs, and thereby provide an evaluation of the labs’ capabilities and provide insight into the feasibility of different analytical methodologies for use with future measurements. KW - Energy gases KW - Real samples KW - Sampling KW - Analysis PY - 2013 SN - 1754-2928 IS - July SP - 1 EP - 28 PB - Queen's Printer and Controller of HMSO CY - Teddington, Middlesex, UK AN - OPUS4-29449 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -