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 - TY - CONF A1 - Tuma, Dirk T1 - Kalorimetrische Bestimmung des Brennwerts nicht-konventioneller Brenngase und Vergleich mit analytischer Methodik T2 - VDI-Expertenforum Thermodynamik-Kolloquium 2013 CY - Hamburg, Germany DA - 2013-10-07 PY - 2013 AN - OPUS4-29274 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tuma, Dirk T1 - Gaslöslichkeiten und Hochdruckphasengleichgewichte in ternären Systemen mit Beteiligung ionischer Flüssigkeiten T2 - Thermodynamik-Kolloquium der DECHEMA e.V. CY - Frankfurt am Main, Germany DA - 2011-10-04 PY - 2011 AN - OPUS4-29340 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Tuma, Dirk T1 - Standards and methods for the analysis of coal mine methane, a "non-conventional" energy gas T2 - GAS 2013 CY - Rotterdam, Netherlands DA - 2013-06-05 PY - 2013 AN - OPUS4-29338 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hernández-Gómez, R. A1 - Tuma, Dirk A1 - Villamanan, M.A. A1 - Mondéjar, M.E. A1 - Chamorro, C.R. T1 - Accurate thermodynamic characterization of a synthetic coal mine methane mixture N2 - In the last few years, coal mine methane (CMM) has gained significance as a potential non-conventional gas fuel. The progressive depletion of common fossil fuels reserves and, on the other hand, the positive estimates of CMM resources as a by-product of mining promote this fuel gas as a promising alternative fuel. The increasing importance of its exploitation makes it necessary to check the capability of the present-day models and equations of state for natural gas to predict the thermophysical properties of gases with a considerably different composition, like CMM. In this work, accurate density measurements of a synthetic CMM mixture are reported in the temperature range from (250 to 400) K and pressures up to 15 MPa, as part of the research project EMRP ENG01 of the European Metrology Research Program for the characterization of non-conventional energy gases. Experimental data were compared with the densities calculated with the GERG-2008 equation of state. Relative deviations between experimental and estimated densities were within a 0.2% band at temperatures above 275 K, while data at 250 K as well as at 275 K and pressures above 10 MPa showed higher deviations. KW - Coal mine methane KW - Density measurements KW - Single sinker densimeter KW - GERG-2008 equation of state PY - 2014 DO - https://doi.org/10.1016/j.jct.2013.09.023 SN - 0021-9614 VL - 68 SP - 253 EP - 259 PB - Academic Press CY - London [u.a.] AN - OPUS4-29450 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lamiel, C. A1 - Lee, Y. R. A1 - Cho, M. H. A1 - Tuma, Dirk A1 - Shim, J.-J. T1 - Enhanced electrochemical performance of nickel-cobalt-oxide@reduced graphene oxide//activated carbon asymmetric supercapacitors by the addition of a redox-active electrolyte N2 - Supercapacitors are an emerging energy-storage system with a wide range of potential applications. In this study, highly porous nickel-cobalt-oxide@reduced graphene oxide (Ni-Co-O@RGO-s) nanosheets were synthesized as an active material for supercapacitors using a surfactant-assisted microwave irradiation technique. The RGO-modified nanocomposite showed a larger specific area, better conductivity, and lower resistivity than the unmodified nanocomposite because the RGO facilitated faster ion diffusion/transport for improved redox activity. The synergistic effect of Ni-Co-O@RGO-s resulted in a high capacitance of 1903 F/g (at 0.8 A/g) in a mixed KOH/redox active K3Fe(CN)6 electrolyte. The asymmetric Ni-Co-O@RGO-s//AC supercapacitor device yielded a high energy density and power density of 39 Wh/kg and 7500 W/kg, respectively. The porous structure and combination of redox couples from both the electrode and electrolyte provided a highly synergistic effect, which improved the performance of the supercapacitor device. KW - Ni-Co oxide KW - Reduced graphene oxide KW - Nanocomposite KW - Supercapacitor PY - 2017 DO - https://doi.org/10.1016/j.jcis.2017.08.003 SN - 0021-9797 SN - 1095-7103 VL - 507 SP - 300 EP - 309 PB - Elsevier Inc. CY - Amsterdam AN - OPUS4-41284 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mady, A. H. A1 - Baynosa, M. L. A1 - Tuma, Dirk A1 - Shim, J.-J. T1 - Facile microwave-assisted green synthesis of Ag-ZnFe2O4@rGO nanocomposites for efficient removal of organic dyes under UV- and visible-light irradiation N2 - Nanocomposites of Ag-ZnFe2O4@reduced graphene oxide (rGO) were synthesized using a one-pot microwave-assisted self-assembly method. The morphology and structure of the Ag-ZnFe2O4@rGO nanocomposites were characterized. The nanocomposites formed with 15.2 wt% rGO showed excellent adsorption properties and high photocatalytic activity for the degradation of methylene blue (MB), rhodamine B (RhB), and methyl orange (MO). The synergistic interactions between Ag, ZnFe2O4, and rGO decreased the aggregation of the nanoparticles (NPs) and increased the surface area, resulting in better absorption in both UV and visible light. Such a structure was helpful for separating the photoexcited electron-hole pairs and accelerating electron transfer. Electrochemical impedance spectroscopy (EIS) revealed a smaller resistance in the solid-state interface layer and charge transfer on the composite surface than that of the bare ZnFe2O4 NPs and ZnFe2O4@rGO nanocomposite. The Ag-ZnFe2O4@rGO nanocomposite could be recovered easily by a magnet and reused five times with no significant decrease in photocatalytic activity. The as-prepared Ag-ZnFe2O4@rGO nanocomposite catalyst could be applied to the removal of hard-to-degrade waste materials owing to its high efficiency in both UV and visible light and its excellent reusability. KW - nanoparticles KW - microwave synthesis KW - photocatalysis PY - 2017 DO - https://doi.org/10.1016/j.apcatb.2016.10.033 SN - 0926-3373 SN - 1873-3883 VL - 203 SP - 416 EP - 427 PB - Elsevier B. V. CY - Amsterdam AN - OPUS4-37962 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tuma, Dirk A1 - Safarov, J. A1 - Sperlich, C. A1 - Namazova, A. A1 - Aliyev, A. A1 - Shahverdiyev, A. A1 - Hassel, E. T1 - Carbon dioxide solubility in 1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium tetrachloroferrate over an extended range of temperature and pressure N2 - Solubility data of carbon dioxide (CO2) in the two ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] and 1-butyl-3-methylimidazolium tetrachloroferrate [BMIM][FeCl4] at T = (273.15-413.15) K and pressures up to p = 4.5 MPa are presented. In Addition to the experiments, a literature review was done to compare the new results with published solubility data. The measurements were carried out using an isochoric method which operates in decrements of deltaT = 20 K within the investigated temperature range and at selected four different pressure steps ranging from a pressure p of around 4.5 MPa to around 0.5 MPa. The solubility of CO2 decreases in both ionic liquids with increasing temperatures. Within the p,T-range investigated, CO2 displayed a solubility in [BMIM][BF4] from a mole fraction x = 0.0117 and a corresponding molality m = 0.0526 mol/kg at T = 413.15 K and p = 0.417 MPa up to x = 0.4876 and m = 4.2094 mol/kg at T = 293.15 K and p = 4.349 MPa. The corresponding values for the solubility in [BMIM][FeCl4] start at a mole fraction x = 0.0268 and a corresponding molality m = 0.0818 mol/kg at T = 413.15 K and p = 0.443 MPa and end at x = 0.5126 and m = 3.1216 mol/kg at T = 293.15 K and p = 4.478 MPa. At a constant temperature, CO2 is better soluble in [BMIM][FeCl4] than in [BMIM][BF4] and the mean value of the solubility difference related to mole fraction x over the pressure range investigated amounts to about 4 % at T = 273.15 K and monotonously increases to about 92 % at T = 413.15 K. Henry's law constant as well as derived thermodynamic properties, such as the Gibbs energy of solvation, the enthalpy of solvation, the entropy of solvation, and the heat capacity of solvation, were calculated and discussed regarding the solute-solvent molecular interactions. KW - Ionic liquid KW - Gas solubility KW - Henry's law constant KW - Solvation properties PY - 2018 DO - https://doi.org/10.1016/j.fluid.2018.03.019 SN - 0378-3812 SN - 1879-0224 VL - 467 SP - 45 EP - 60 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-44892 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tuma, Dirk A1 - Hernández-Gomez, R. A1 - Pérez, E. A1 - Chamorro, C. R. T1 - Accurate experimental (p, ρ, and T) data for the introduction of hydrogen into the natural gas grid (II): Thermodynamic characterization of the methane−hydrogen binary system from 240 to 350 K and pressures up to 20 MPa N2 - Most of the experimental density data of the methane−hydrogen binary system available at the time of the development of the equation of state for natural gases and related mixtures, GERG-2008, at temperatures above 270 K were limited to hydrogen contents higher than 0.20 (amount-of-substance fraction). On the contrary, for mixtures with hydrogen contents lower than 0.20, experimental data were limited to temperatures below 270 K. This work intends to close the gap and provides accurate experimental (p, ρ, and T) data for three binary mixtures of methane and hydrogen, (0.95 CH4 + 0.05 H2), (0.90 CH4 + 0.10 H2), and (0.50 CH4 + 0.50 H2), at temperatures of 240, 250, 260, 275, 300, 325, and 350 K, thus extending the range of available experimental data to higher temperatures for mixtures with hydrogen contents lower than 0.20 and, accordingly, to lower temperatures for mixtures with hydrogen contents higher than 0.20. The density measurements were performed by using a single-sinker densimeter with magnetic suspension coupling at pressures up to 20 MPa. Experimental data were compared to the corresponding densities calculated from the GERG-2008 and the AGA8-DC92 equations of state, respectively. The experimental data are within the uncertainty of both equations of state, except at the lower temperatures of 240 and 250 K and pressures over 14 MPa for the mixtures with a hydrogen content of 0.05 and 0.10, respectively. The virial coefficients B(T, x) and C(T, x), as well as the second interaction virial coefficient B12(T) for the methane−hydrogen binary system, were also calculated from the experimental data set at temperatures from 240 to 350 K using the virial equation of state. KW - Volumetric data KW - GERG-2008 equation of state KW - Hydrogen-containing mixture KW - Single-sinker densimeter PY - 2018 DO - https://doi.org/10.1021/acs.jced.7b01125 SN - 0021-9568 VL - 63 IS - 5 SP - 1613 EP - 1630 PB - ACS Publications CY - Washington DC AN - OPUS4-44890 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Flores, E. A1 - Idrees, F. A1 - Moussay, P. A1 - Viallon, J. A1 - Wielgosz, R. A1 - Fernández, T. A1 - Ramírez, S. A1 - Rojo, A. A1 - Shinji, U. A1 - Waldén, J. A1 - Sega, M. A1 - Sang-Hyub, O. A1 - Macé, T. A1 - Couret, C. A1 - Qiao, H. A1 - Smeulders, D. A1 - Guenther, F.R. A1 - Thorn, W.J. III A1 - Tshilongo, J. A1 - Ntsasa, N.G. A1 - Stovcík, V. A1 - Valková, M. A1 - Konopelko, L. A1 - Gromova, E. A1 - Nieuwenkamp, G. A1 - Wessel, R. M. A1 - Milton, M. A1 - Harling, A. A1 - Vargha, G. A1 - Tuma, Dirk A1 - Kohl, Anka A1 - Schulz, Gert T1 - Final report on international comparison CCQM-K74: Nitrogen dioxide, 10 µmol/mol N2 - There is a high international priority attached to activities which reduce NOx in the atmosphere. The current level of permitted emissions is typically between 50 µmol/mol and 100 µmol/mol, but lower values are expected in the future. Currently, ambient air quality monitoring regulations also require the measurement of NOx mole fractions as low as 0.2 µmol/mol. The production of accurate standards at these levels of mole fractions requires either dilution of a stable higher concentration gas standard or production by a dynamic technique, for example one based on permeation tubes. The CCQM-K74 key comparison was designed to evaluate the level of comparability of National Metrology Institutes' measurement capabilities and standards for nitrogen dioxide (NO2) at a nominal mole fraction of 10 µmol/mol. The measurements of this key comparison took place from June 2009 to May 2010. Seventeen laboratories took part in this comparison coordinated by the BIPM and VSL. The key comparison reference value was based on BIPM measurement results, and the standard measurement uncertainty of the reference value was 0.042 µmol/mol. This key comparison demonstrated that the results of the majority of the participants agreed within limits of ±3% relative to the reference value. The results of only one laboratory lay significantly outside these limits. Likewise this comparison made clear that a full interpretation of the results of the comparison needed to take into account the presence of nitric acid (in the range 100 nmol/mol to 350 nmol/mol) in the cylinders circulated as part of the comparison, as well as the possible presence of nitric acid in the primary standards used by participating laboratories. 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). DatesIssue 1A (Technical Supplement 2012) KW - Ringversuch KW - NO2 KW - Spurenverunreinigungen KW - Meßverfahren PY - 2012 DO - https://doi.org/10.1088/0026-1394/49/1A/08005 SN - 0026-1394 SN - 1681-7575 VL - 49 IS - 08005 SP - 1 EP - 117 PB - Inst. of Physics Publ. CY - Bristol AN - OPUS4-25927 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nieuwenkamp, G. A1 - Wessel, R. M. A1 - van der Veen, A.M.H. A1 - Ziel, P. R. A1 - Han, Q. A1 - Tuma, Dirk A1 - Woo, J.-C. A1 - Fuko, J.T. A1 - Szilágyi, N. A1 - Büki, T. A1 - Konopelko, L. A1 - Kustikov, Y.A. A1 - Popova, T.A. A1 - Pankratov, V.V. A1 - Pir, M.N. A1 - Nazarov, E.V. A1 - Ehvalov, L.V. A1 - Timofeev, A.U. A1 - Kuzmina, T.A. A1 - Meshkov, A.V. A1 - Valková, M. A1 - Pätoprsty, V. A1 - Downey, M. A1 - Vargha, G. A1 - Brown, A. A1 - Milton, M. T1 - International comparison CCQM-K77: Refinery gas N2 - Refinery gas is a complex mixture of hydrocarbons and non-combustible gases (e.g., carbon monoxide, carbon dioxide, nitrogen, helium). It is obtained as part of the refining and conversion of crude oil. This key comparison aims to evaluate the measurement capabilities for these types of mixtures. The results of the key comparison indicate that the analysis of a refinery-type gas mixture is for some laboratories a challenge. Overall, four laboratories (VSL, NIM, NPL and VNIIM) have satisfactory results. The results of some participants highlight some non-trivial issues, such as appropriate separation between saturated and unsaturated hydrocarbons, and issues with the measurement of nitrogen, hydrogen and helium. 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). DatesIssue 1A (Technical Supplement 2012) KW - Ringversuch KW - Raffineriegas KW - Chromatographische Analyse PY - 2012 DO - https://doi.org/10.1088/0026-1394/49/1A/08003 SN - 0026-1394 SN - 1681-7575 VL - 49 IS - 08003 SP - 1 EP - 71 PB - Inst. of Physics Publ. CY - Bristol AN - OPUS4-25931 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -