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- Ringversuch (4)
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- Spurenverunreinigungen (2)
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Organisationseinheit der BAM
This pilot study compares the performance of participants in analyzing gas mixtures of nitrogen dioxide in nitrogen by comparison with in-house gravimetric standards using Fourier transformed infrared spectroscopy (FT-IR). In this study the same gas mixtures were used as in the key comparison CCQM-K74, which was designed to evaluate the level of comparability of National Metrology Institutes' measurement capabilities for nitrogen dioxide (NO2) at a nominal mole fraction of 10 µmol/mol. In the comparison CCQM-K74 most of the participants used chemiluminescence, with a small number using UV absorption or FT-IR spectroscopy, and thus it is of interest to improve understanding of the comparative performance of these techniques because they do not exhibit any cross-sensitivity to nitric acid (HNO3), which was known to be present in the mixtures used for the comparison.
The results of this pilot study indicate good consistency and a level of agreement similar to that reported in the comparison CCQM-K74, demonstrating that FT-IR can be operated as a comparison method when calibrated with appropriate gas standards and can achieve similar measurement uncertainties to chemiluminescence and UV absorption techniques.
An additional pilot study, CCQM-P110-B2, was conducted on the same gas mixtures in parallel with this pilot study. The second study addressed FT-IR spectroscopy when used to measure the gas mixtures with respect to reference spectra. The results of this second study will be reported elsewhere.
Main text. To reach the main text of this paper, click on Final Report.
The final report has been peer-reviewed and approved for publication by the CCQM-GAWG.
DatesIssue 1A (Technical Supplement 2012)
Amphiphilic amino acids represent promising scaffolds for biologically active soft matter. In order to understand the bulk self-assembly of amphiphilic amino acids into thermotropic liquid crystalline phases and their biological properties a series of tyrosine ionic liquid crystals (ILCs) was synthesized, carrying a benzoate unit with 0–3 alkoxy chains at the tyrosine unit and a cationic guanidinium head group. Investigation of the mesomorphic properties by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (WAXS, SAXS) revealed smectic A bilayers (SmAd) for ILCs with 4-alkoxy- and 3,4-dialkoxybenzoates, whereas ILCs with 3,4,5-trisalkoxybenzoates showed hexagonal columnar mesophases (Colh ), while different counterions had only a minor influence. Dielectric measurements revealed a slightly higher dipole moment of non-mesomorphic tyrosine-benzoates as compared to their mesomorphic counterparts. The absence of lipophilic side chains on the benzoate unit was important for the biological activity. Thus, non-mesomorphic tyrosine benzoates and crown ether benzoates devoid of additional side chains at the benzoate unit displayed the highest cytotoxicities (against L929 mouse fibroblast cell line) and antimicrobial activity (against Escherichia coli DTolC and Staphylococcus aureus) and promising selectivity ratio in favour of antimicrobial activity.
In this paper we present results of our recent efforts to understand the mechanical interface behaviour of single-walled carbon nanotubes (CNTs) embedded in metal matrices. We conducted experimental pull-out tests of CNTs embedded in Pd or Au and found Maximum forces in the range 10 - 102 nN. These values are in good agreement with forces obtained from molecular Dynamics simulations taking into account surface functional Groups (SFGs) covalently linked to the CNT material. The dominant failure mode in experiment is a CNT rupture, which can be explained with the presence of SFGs. To qualify the existence of SFGs on our used CNT material, we pursue investigations by means of fluorescence labeling of surface species in combination with Raman imaging. We also report of a tensile test system to perform pull-out tests inside a transmission electron microscope to obtain in situ images of CNT-metal interfaces under mechanical loads at the atomic scale.
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)
Bei der Bewertung der Verlässlichkeit der im Labor gewonnenen Prüfergebnisse spielen Ringversuche eine entscheidende Rolle. Die Bundesanstalt für Materialforschung und -prüfung (BAM) unterstützt deshalb den weiteren Ausbau des Ringversuchsprogramms des im Jahr 2007 gegründeten Kompetenzzentrums zur Qualitätssicherung für Prüfungen von Gefahrgütern und Gefahrstoffen auf physikalische Gefahren (Centre for quality assurance for testing of dangerous goods and hazardous substances, CEQAT-DGHS).
Bei allen bisher untersuchten Prüfmethoden besteht ein Verbesserungsbedarf. Die RV müssen daher zunächst auf die Methodenentwicklung, -verbesserung und -validierung abzielen und nicht auf Leistungstests.
Bei der Bewertung der Verlässlichkeit der im Labor gewonnenen Prüfergebnisse spielen Ringversuche eine entscheidende Rolle. Die Bundesanstalt für Materialforschung und –prüfung (BAM) unterstützt deshalb den weiteren Ausbau des Ringversuchsprogramms des im Jahr 2007 gegründeten Kompetenzzentrums zur Qualitätssicherung für Prüfungen von Gefahrgütern und Gefahrstoffen auf physikalische Gefahren (Centre for quality assurance for testing of dangerous goods and hazardous substances, CEQAT-DGHS).
Bei allen bisher untersuchten Prüfmethoden besteht ein Verbesserungsbedarf. Die RV müssen daher zunächst auf die Methodenentwicklung, -verbesserung und -validierung und auf die Bestimmung der Messunsicherheit der jeweiligen Prüfmethode abzielen und nicht auf Leistungstests.
Bei der Bewertung der Verlässlichkeit der im Labor gewonnenen Prüfergebnisse spielen Ringversuche eine entscheidende Rolle. Die Bundesanstalt für Materialforschung und –prüfung (BAM) unterstützt deshalb den weiteren Ausbau des Ringversuchsprogramms des im Jahr 2007 gegründeten Kompetenzzentrums zur Qualitätssicherung für Prüfungen von Gefahrgütern und Gefahrstoffen auf physikalische Gefahren (Centre for quality assurance for testing of dangerous goods and hazardous substances, CEQAT-DGHS).
Bei allen bisher untersuchten Prüfmethoden besteht ein Verbesserungsbedarf. Die RV müssen daher zunächst auf die Methodenentwicklung, -verbesserung und -validierung und auf die Bestimmung der Messunsicherheit der jeweiligen Prüfmethode abzielen und nicht auf Leistungstests.
Continuously tuneable liquid crystal based stripline phase shifter realised in LTCC technology
(2015)
This work presents the design, fabrication and measurements of a low temperature cofired ceramic (LTCC) integrated liquid crystal (LC) phase shifter. The effective permittivity of the phase shifter and therefore its differential phase shift can be tuned continuously by orienting the LC directors with electric fields. The phase-shift demonstrator is designed for Ka-band frequencies around 30 GHz and represents a stripline filled with LC, embedded inside an LTCC multilayer structure, which provides a space-qualified and hermetically-sealed LC cavity within an RF-capable material system. The total length of the device is 37 mm while the phase shifting LC section has a length of 14.6 mm. At 30 GHz it exhibits a differential phase shift of 60° with an insertion loss around 6 dB, resulting in a figure of merit around 10°/dB. An advantage is that the insertion loss is nearly independent of the tuning state of the LC. The response time of the phase shifter, depending on the desired LC orientation, is between 62 ms and 37 s.