Articles | Volume 4, issue 2
J. Sens. Sens. Syst., 4, 263–269, 2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Special issue: Sensor/IRS2 2015
Regular research article 17 Aug 2015
Regular research article | 17 Aug 2015
Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: correlation of dielectric properties with ammonia storage
M. Dietrich et al.
No articles found.
Robin Werner, Jaroslaw Kita, Michael Gollner, Florian Linseis, and Ralf Moos
J. Sens. Sens. Syst., 10, 71–81,Short summary
A novel, low-cost measurement device for simultaneous high temperature measurements of the electrical conductivity and Hall coefficient has been developed. Simulations were used to design a suitable screen-printed planar platinum heating structure that generates temperatures of up to 600 °C. Simulations of the temperature distribution have been validated using thermal imaging. Measurements were compared with data from the literature to validate the functionality of the novel device.
Anastasiya Ruchets, Nils Donker, Jens Zosel, Daniela Schönauer-Kamin, Ralf Moos, Ulrich Guth, and Michael Mertig
J. Sens. Sens. Syst., 9, 355–362,Short summary
A commercial solid electrolyte gas sensor of the type "Pt|YSZ|Pt, air" based on yttria-stabilized zirconia for colorimetric oxygen detection was operated in optimized dynamic electrochemical modes. Cyclic voltammetry and square-wave voltammetry were used for the detection of NO and O2 in N2 in the temperature range between 550 and 750 °C. Due to the differences of electrode kinetics of the single components it is possible to detect these redox active gases selectively and quasi-simultaneously.
Julia Herrmann, Gunter Hagen, Jaroslaw Kita, Frank Noack, Dirk Bleicker, and Ralf Moos
J. Sens. Sens. Syst., 9, 327–335,Short summary
In this contribution, an inexpensive and robust impedimetric NOx sensor is presented. The impedance of a functional thick film depends selectively on the NOx concentration in the exhaust but shows a dependency on the oxygen concentration. Therefore, an additional temperature-independent resistive oxygen sensor structure was integrated on the same sensor platform. It serves not only to determine the oxygen concentration in the exhaust, but also to correct the oxygen dependency of the NOx sensor.
Nils Donker, Anastasiya Ruchets, Daniela Schönauer-Kamin, Jens Zosel, Ulrich Guth, and Ralf Moos
J. Sens. Sens. Syst., 9, 293–300,Short summary
Symmetrical Pt | YSZ | Pt–NO gas sensors were produced with frit-containing and fritless Pt electrodes and fired between 950 and 1300 °C. The sensors were operated by pulsed polarization. With fritless pastes, the sensors responded significantly higher. The firing temperature affects the sensitivity only slightly. The low NO sensitivity of the frit-containing electrodes was attributed to a blocking effect at the triple-phase boundaries that inhibits the oxygen transport through the sensor.
Stefanie Walter, Andreas Bogner, Gunter Hagen, and Ralf Moos
J. Sens. Sens. Syst., 8, 49–56,Short summary
A planar resonant radio-frequency gas sensor was equipped with an integrated heater. By simulative geometry optimization it now can be operated up to 700 °C. Sensitive materials with gas-dependent dielectric properties at higher temperatures can now be used. By coating the sensor with zeolite, ammonia could be detected. Depending on the working temperature, the sensor returns either a dosimeter signal (low temperatures) or a gas-concentration-dependent radio-frequency signal (high temperatures).
Murat Bektas, Thomas Stöcker, Angelika Mergner, Gunter Hagen, and Ralf Moos
J. Sens. Sens. Syst., 7, 289–297,Short summary
We prepared BaFe(1-x)-0.01Al0.01TaxO3-δ (BFATx) thick films with x between 0.1 and 0.4 at room temperature using the aerosol deposition method and we measured Seebeck coefficients and conductivities between 600 and 800 °C at different oxygen concentrations. Deposited on a transducer that includes a heater, equipotential layers, and electrode structures, a dual thermoelectric–resistive oxygen sensor with almost temperature-independent characteristics of both measurands was realized using BFAT30.
Gunter Hagen, Antonia Harsch, and Ralf Moos
J. Sens. Sens. Syst., 7, 79–84,Short summary
Monitoring hydrocarbon concentrations in automotive exhausts is affected by flow rate changes. The signal of thermoelectric gas sensors is a thermovoltage. Its origin is a temperature difference that depends on the flow rate. To avoid this noise effect, the sensor can be installed in a defined bypass position. As shown by simulation and experiments, the gas flow around the sensor is almost turbulence-free and the signal only depends on the hydrocarbon concentration and not on the flow rate.
Thomas Ritter, Sven Wiegärtner, Gunter Hagen, and Ralf Moos
J. Sens. Sens. Syst., 6, 395–405,Short summary
A planar thermoelectric gas sensor is modeled. By coupling all influences (fluid flow, gas diffusion, heat transfer, chemical reactions, and electrical properties) a model was set up that mirrors the sensor behavior precisely, as the comparison with experimental data shows. The coupling of 3-D and 1-D geometry enables to calculate the temperature distribution, fluid flow, and the gas concentration distribution in the 3-D model, while the chemical reactions are very accurately calculated in 1-D.
Franz Schubert, Michael Gollner, Jaroslaw Kita, Florian Linseis, and Ralf Moos
J. Sens. Sens. Syst., 5, 381–388,Short summary
An FEM model is used to improve the sensor design of a Tian–Calvet calorimeter. By modifying the basic part of the sensor (a sensor disc based on low temperature co-fired ceramics), the sensitivity was increased by a factor of 3. The model was validated and the sensors were calibrated. Indium and tin samples were measured. The melting temperatures show a deviation of 0.2 K while the enthalpy was measured with a precision better than 1 %. The values for tin deviate by less than 2 % from literature.
Franz Schubert, Michael Gollner, Jaroslaw Kita, Florian Linseis, and Ralf Moos
J. Sens. Sens. Syst., 5, 205–212,Short summary
Initial steps to apply a new ceramic multi-layer sensor for a Tian–Calvet calorimeter are shown. The FEM-developed sensor consists of stacked ceramic discs and insulation rings. The functionality of the sensor disc was proven up to 600 °C and the entire stack was tested at room temperature. The resolution was 5 µW and the sensitivity was 8.5 µV mW−1. The new sensor shows similar specifications as commercial devices and presents a good starting point for future high temperature applications.
F. Schubert, S. Wollenhaupt, J. Kita, G. Hagen, and R. Moos
J. Sens. Sens. Syst., 5, 25–32,Short summary
A manufacturing process for a planar binary lambda sensor is shown. By joining the heating and the sensing components via glass soldering with a joining temperature of 850 °C, a laboratory platform has been established that allows the manufacturing of two independent parts in HTCC technology with electrodes that are post-processed at lower temperatures, as is required for mixed-potential sensors. The concept has been proved by comparing the device with a commercial sensor.
S. Fischer, D. Schönauer-Kamin, R. Pohle, M. Fleischer, and R. Moos
J. Sens. Sens. Syst., 4, 321–329,Short summary
Thimble-type lambda probes that are known for their robustness in harsh exhausts can also be used as an NOx sensor by applying the pulsed polarization technique. This study evaluates in detail the influence of temperature on the NO sensitivity, so that an optimum operating point can be derived. Stepwise NO concentration changes between 0 and 12.5 ppm in synthetic exhausts demonstrate the high potential of this concept.
P. Fremerey, A. Jess, and R. Moos
J. Sens. Sens. Syst., 4, 143–149,Short summary
A concept to measure in situ sulfidation of silica pellet catalysts loaded with nickel is evaluated. During sulfidation between 100 and 400°C nickel sulfides form. The electrical impedance of the pellets was recorded in situ. At first, the particles are highly insulating but during sulfidation their conductivity increases by decades. Since nickel sulfides are less conductive than nickel, the strong conductivity increase may be due to conducting percolation paths that form during sulfidation.
M. Bektas, D. Hanft, D. Schönauer-Kamin, T. Stöcker, G. Hagen, and R. Moos
J. Sens. Sens. Syst., 3, 223–229,
I. Marr, A. Groß, and R. Moos
J. Sens. Sens. Syst., 3, 29–46,
P. Bartscherer and R. Moos
J. Sens. Sens. Syst., 2, 95–102,
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J. Sens. Sens. Syst., 10, 37–42,Short summary
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J. Sens. Sens. Syst., 8, 329–333,Short summary
We came across some problems with the current measurement shunts while building a transfer normal power analyzer for 150 kHz within a cooperation project of the manufacturer ZES ZIMMER along with PTB, the National Metrology Institute of Germany and Bundesnetzagentur Berlin. We decided to utilize simulations with the numerical field simulation program Fast Henry to determine the cause of this frequency behavior. We found adequate justification and give recommendations for the shunt manufacturing.
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Thin tantalum films generated by glancing angle deposition serve as functional optical layers. Serial sectioning by a focused ion beam combined with scanning electron microscopy of the slices generates stacks of highly resolved images of this film. Dedicated image processing reconstructs the spatial structure such that 3-D image analysis yields geometric information that can be related to the optical performance.
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J. Sens. Sens. Syst., 8, 243–250,Short summary
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J. Sens. Sens. Syst., 7, 169–181,Short summary
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Günter Schultes, Hanna Schmid-Engel, Silvan Schwebke, and Ulf Werner
J. Sens. Sens. Syst., 7, 1–11,Short summary
This research is about future sensor devices for force, pressure, and weight. The core of such sensors for mechanical quantities is a thin film that reacts to deformation. We are developing new sensor films with higher output. Different compositions of metal containing carbon films are examined. Most preferable and stable films contain nickel and carbon. The microscopic film morphology is uncovered. Electron tunneling between nanoparticles is responsible for the very sensitive reaction.
Sabrina Amrehn, Xia Wu, and Thorsten Wagner
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Indium oxide inverse opal is a promising new material for optical gas sensors. The photonic properties caused by the inverse opal structure can be utilized to read out the sensors’ electronical state by optical methods. The maintenance of good thermal stability of transducer material during operation is a minimum requirement. We present results on the synthesis and investigation of the structural stability of the In2O3 inverse opal structure up to a temperature of 550 °C (limit of substrate).
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J. Sens. Sens. Syst., 5, 113–123,Short summary
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J. Sens. Sens. Syst., 4, 271–280,
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In this paper we show that for radially symmetric piezoceramic disks non-zero sensitivity of the electrical impedance to the whole material parameter set can be computed using a system of 3-ring electrodes and non-uniform electrical excitation. We formulate an optimisation problem for increasing this sensitivity. However, the system displays multiple optimal configurations for the radii of said ring electrodes and we have shown some results from optimising such configurations using simulations.
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J. Sens. Sens. Syst., 4, 133–136,Short summary
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Beulertz, G., Herbst, F., Hagen, G., Fritsch, M., Gieshoff, J., and Moos, R.: Microwave Cavity Perturbation as a Tool for Laboratory In Situ Measurements of the Oxidation State of Three Way Catalysts, Top. Catal., 56, 405–409, https://doi.org/10.1007/s11244-013-9987-3, 2013.
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The effect of stored ammonia on the complex dielectric permittivity of H-ZSM-5 zeolites with varying storage site density was observed between 200 and 300 °C under reaction conditions by microwave cavity perturbation. Polarization and dielectric losses were differently affected. The sensitivity of the polarization to stored ammonia is almost independent, the sensitivity of the dielectric losses strongly dependent on the storage site density. The results can be explained by proton hopping.
The effect of stored ammonia on the complex dielectric permittivity of H-ZSM-5 zeolites with...