| 1. |
- Baranzahi, Amir, et al.
(författare)
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Response of metal-oxide-silicon carbide sensors to simulated and real exhaust gases
- 1997
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 43:1-3, s. 52-59
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Tidskriftsartikel (refereegranskat)abstract
- Field effect devices based on catalytic metal-oxide-silicon carbide (MOSiC) structures can be used as high temperature gas sensors. The devices are sensitive to hydrocarbons and hydrogen and can be operated up to at least 900 degrees C, which make them suitable for several combustion applications, Simulated and real exhaust gases from a car engine have been studied at sensor temperatures from 200 to 650 degrees C, and it was round that the sensor signal is high for excess hydrocarbon and low for excess oxygen. The response time is less than 100 ms and only a small degradation of the devices was observed after several days of operation. The devices also react to changes of the gas composition In the fuel-rich and fuel-lean region. The devices show an interesting temperature dependence in the fuel rich region.
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| 2. |
- Tobias, Peter, et al.
(författare)
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Influence of gas consumption on the response of metal oxide silicon carbide sensors to exhaust gases
- 1998
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Ingår i: EUROSENSORS XII, VOLS 1 AND 2. - : Institute of Physics Publishing (IOPP). - 0750305363 ; , s. 249-252
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Silicon carbide based Schottky diodes w th catalytic gate metals are promising for diagnosis of exhaust gas from combustion engines. The forward voltage measured at a constant current changes from a low level in reducing gases to a high level in oxidising gases. Factorial design in two levels on synthetic exhausts reveal interesting details of the influence of the different components on the sensor signal. Contrary to earlier experiments, an increase of the concentration of hydrocarbons and carbon monoxide increases the signal level. Hydrogen gas behaves as expected, an increased concentration increases the signal level. The total area of catalytic metal was much smaller in the new experiment and the different behavior of the sensor signal can probably be explained by consumption cf gases on catalytic metal surfaces.
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| 3. |
- Torsi, Luisa, et al.
(författare)
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Organic thin-film transistors for inorganic substance monitoring
- 2009. - 1
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Ingår i: Organic electronics in Sensors and Biotechnology. - New York : McGraw-Hill Companies Inc. - 9780071596756 ; , s. 51-91
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Develop high-performance, field-deployable organic semiconductor-based biological, chemical, and physical sensor arrays using the comprehensive information contained in this definitive volume. Organic Electronics in Sensors and Biotechnology presents state-of-the-art technology alongside real-world applications and ongoing R & D.Learn about light, temperature, and pressure monitors, integrated flexible pyroelectric sensors, sensing of organic and inorganic compounds, and design of compact photoluminescent sensors. You will also get full details on organic lasers, organic electronics in memory elements, disease and pathogen detection, and conjugated polymers for advancing cellular biology.Monitor organic and inorganic compounds with OFETsCharacterize organic materials using impedance spectroscopyWork with organic LEDs, photodetectors, and photovoltaic cellsForm flexible pyroelectric sensors integrated with OFETsBuild PL-based chemical and biological sensing modules and arraysDesign organic semiconductor lasers and memory elementsUse luminescent conjugated polymers as optical biosensorsDeploy polymer-based switches and ion pumps at the microfluidic level
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| 4. |
- Wingbrant, Helena, et al.
(författare)
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Using a MISiCFET device as a cold start sensor
- 2003
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Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 63:1-3, s. 295-303
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Tidskriftsartikel (refereegranskat)abstract
- As a consequence of the formation of water droplets in the car engine at cold start, the fragile ZrO2 λ sensor cannot be heated until the engine is sufficiently warm. A possibility to shorten the time before closed loop λ control would decrease the exhaust emission. As a solution to this problem, the metal insulator silicon carbide field effect transistor (MISiCFET) sensor, which presumably is more thermo shock resistant than the ZrO2 sensor, could be used at cold start. The requirements for a cold start sensor are, among others, sensitivity to λ (air to fuel ratio) close to stochiometry, selectivity to λ and high speed of response. In this communication, the possibility of using the MISiCFET sensor at cold start is treated. The sensor consists of a SiC based MOSFET device with a buried channel design and a catalytic gate metal of 10 nm TaSix and 100 nm Pt. The response depends linearly on λ at 500 °C. The sensitivity of the device has been tested both in artificial atmospheres and in an engine. Two-level factorial designed experiments showed a high selectivity to λ compared to other gases such as CO, hydrocarbons, NOx and H2. The response time was found to be <10 ms at 500 °C when changing from an oxidizing to a reducing atmosphere. The MISiCFET sensor response showed interesting differences in λ stairs when the λ-value was varied by changing the oxygen, hydrogen or CO concentration. The results show that the MISiCFET sensor is a promising choice as a future cold start sensor.
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| 5. |
- Basu, P. K., et al.
(författare)
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Schottky Junction Methane Sensors using Electrochmically Grown Nanocrystalline-Nanoporous ZnO Thin Films
- 2009
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Ingår i: Journal of Sensors. - : Hindawi Publishing Corporation. - 1687-725X .- 1687-7268. ; 2009:790476, s. 1-9
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Nanocrystalline-nanoporous ZnO thin films were prepared by an electrochemical anodization method, and the films were tested as methane sensors. It was found that Pd-Ag catalytic contacts showed better sensing performance compared to other noble metal contacts like Pt and Rh. The methane sensing temperature could be reduced to as low as 100°C by sensitizing nanocrystalline ZnO thin films with Pd, deposited by chemical method. The sensing mechanism has been discussed briefly.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Bounechada, Djamela, et al.
(författare)
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Vibrational analysis of SO2 on Pt / SiO2 system
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In situ diffuse reflectance infrared Fourier transformed spectroscopy was used to study the interactions of SOx species with Pt/SiO2 between 200 and 400°C, and for SO2 concentrations between 10 and 50 ppm, which represents a concentration range where MISFET sensors exhibit good responses. In parallel, first-principles calculations have been carried out to support the experimental interpretations. It was found that sulfate species were formed on the silica surface, accompanied with removal/rearrangement of silanol groups upon exposure to SO2. Both experimental and theoretical calculations also suggest that the surface species were only formed after SO2 oxidation to SO3 on the metal surface. These evidences support the idea of SO2 oxidation to SO3 as the first step in the process of sulfate formation, followed by spillover of SO3 to the oxide, and finally the formation of sulfate species on the hydroxyl positions on the oxide. The results also indicate that the sulfate formation on silica depends both on the temperature and the SO2 concentration. Furthermore, hydrogen exposure was shown to be efficient for sulfur removal from the silica surface.
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| 10. |
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| 11. |
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| 12. |
- Bur, Christian, et al.
(författare)
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Temperature cycled operation of SiC field effect gas sensors: increasing the selectivity for improved sensor systems
- 2011
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Ingår i: AIP. Conf. Proc ISOEN 2011 vol 1362. ; , s. 91-92
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Konferensbidrag (refereegranskat)abstract
- In order to detect and quantify nitrogen oxides (NOx) in a mixture of typical exhaust gases a diode coupled FET has been investigated using Temperature Cycled Operation. This approach, originally developed for metal oxide gas sensors, is quite new for GasFETs but preliminary studies proved that it is suitable for GasFETs as well. In this paper the basic concept was improved by a temperature cycle tailored to NOx detection. Multivariate statistics have been used to evaluate the sensor data. Measurements have shown that with a piecewise extraction of features, a quantification of NO with additional NO2 is possible in the background of exhaust gases. Thus, the detection of NOx and especially the determination of the concentration can be improved.
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| 13. |
- Darmastuti, Zhafira, et al.
(författare)
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Detection mechanism studies of SO2 on Pt / SiO2 system
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Experiment was performed with Pt-gate SiC-FET sensors to study the detection mechanism of the sensors. The sensing measurement showed that oxygen influenced the response quite strongly. The sensor response became larger in the presence of oxygen. Experiment with mass spectroscopy indicated the formation of SO3 during the sensing measurement. Further experiment with DRIFT spectroscopy showed the formation of sulfate species on the oxide surface, accompanied by the disappearance of the silanol groups. An explanatory model was built based on quantum-chemical calculations. The results strengthened the experimental results by showing that it was more energetically favorable for SO2 to oxidize into SO3 before being adsorbed on the oxide surface. It was also observed that the overall adsorption reaction was exothermic, the activation energy for the SO2 oxidation was 48,75 kJ/mol, and the rate limiting step was the desorption of SO3 from the Pt surface.
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| 14. |
- Darmastuti, Zhafira, et al.
(författare)
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SiC-FET methanol sensors for process control and leakage detection
- 2013
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 187:SI, s. 553-562
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Tidskriftsartikel (refereegranskat)abstract
- Two types of SiC based field effect transistor sensors, with Pt or Ir gate, were tested to detect methanol in the concentration range of 0–1600 ppm for both process control and leak detection applications. The methanol response was investigated both with and without oxygen, since the process control might be considered as oxygen free application, while the sensor is operated in air during leak detection. Pt sensors offered very fast response with appreciably high response magnitude at 200 °C, while Ir sensors showed both higher response and response time up to 300 °C, but this decreased considerably at 350 °C. Cross sensitivity effect in presence of oxygen, hydrogen, propene and water vapor was also investigated. The presence of oxygen improved the response of both sensors, which is favorable for the leak detection application. Hydrogen had a large influence on the methanol response of both sensors, propene had a negligible influence, while water vapor changed direction of the methanol response for the Pt sensor. The detection mechanism and different sensing behavior of Pt and Ir gate sensors were discussed in the light of model reaction mechanisms derived from hybrid density-functional theory quantum-chemical calculations.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Keehnen, Naomi L.P., et al.
(författare)
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A Population Genomic Investigation of Immune Cell Diversity and Phagocytic Capacity in a Butterfly
- 2021
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Ingår i: Genes. - : MDPI AG. - 2073-4425. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- Insects rely on their innate immune system to successfully mediate complex interactions with their internal microbiota, as well as the microbes present in the environment. Given the variation in microbes across habitats, the challenges to respond to them are likely to result in local adaptations in the immune system. Here we focus upon phagocytosis, a mechanism by which pathogens and foreign particles are engulfed in order to be contained, killed, and processed. We investigated the phenotypic and genetic variation related to phagocytosis in two allopatric populations of the butterfly Pieris napi. Populations were found to differ in their hemocyte composition and overall phagocytic capability, driven by the increased phagocytic propensity of each cell type. Yet, genes annotated to phagocytosis showed no large genomic signal of divergence. However, a gene set enrichment analysis on significantly divergent genes identified loci involved in glutamine metabolism, which recently have been linked to immune cell differentiation in mammals. Together these results suggest that heritable variation in phagocytic capacity arises via a quantitative trait architecture with variation in genes affecting the activation and/or differentiation of phagocytic cells, suggesting them as potential candidate genes underlying these phenotypic differences.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Malik, Azhar, et al.
(författare)
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A Potential Soot Mass Determination Method from Resistivity Measurement of Thermophoretically Deposited Soot
- 2011
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Ingår i: AEROSOL SCIENCE AND TECHNOLOGY. - : Taylor and Francis. - 0278-6826 .- 1521-7388. ; 45:2, s. 284-294
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Tidskriftsartikel (refereegranskat)abstract
- Miniaturized detection systems for nanometer-sized airborne particles are in demand, for example in applications for onboard diagnostics downstream particulate filters in modern diesel engines. A soot sensor based on resistivity measurements was developed and characterized. This involved generation of soot particles using a quenched co-flow diffusion flame; depositing the particles onto a sensor substrate using thermophoresis and particle detection using a finger electrode structure, patterned on thermally oxidized silicon substrate. The generated soot particles were characterized using techniques including Scanning Mobility Particle Sizer for mobility size distributions, Differential Mobility Analyzer-Aerosol Particle Mass analyzer for the mass-mobility relationship, and Transmission Electron Microscopy for morphology. The generated particles were similar to particles from diesel engines in concentration, mobility size distribution, and mass fractal dimension. The primary particle size, effective density and organic mass fraction were slightly lower than values reported for diesel engines. The response measured with the sensors was largely dependent on particle mass concentration, but increased with increasing soot aggregate mobility size. Detection down to cumulative mass as small as 20-30 mu g has been demonstrated. The detection limit can be improved by using a more sensitive resistance meter, modified deposition cell, larger flow rates of soot aerosol and modifying the sensor surface.
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| 23. |
- Mikalo, RP, et al.
(författare)
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Comparison of HF and ozone treated SiC surfaces
- 2000
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 353-3, s. 219-222
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Tidskriftsartikel (refereegranskat)abstract
- Single crystals of SiC were etched in hydrofluoric acid to remove the native oxide. Ozone exposure at room temperature is shown to give an oxide of about 0.7nm. The differences of interface and bulk oxides regarding their elemental composition and their oxidation states are reported as determined by photoelectron spectroscopy utilizing synchrotron radiation.
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| 24. |
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| 25. |
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| 26. |
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| 27. |
- Sator, Lea, et al.
(författare)
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Overdiagnosis of COPD in Subjects With Unobstructed Spirometry A BOLD Analysis
- 2019
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Ingår i: Chest. - : Elsevier BV. - 0012-3692 .- 1931-3543. ; 156:2, s. 277-288
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: There are several reports on underdiagnosis of COPD, while little is known about COPD overdiagnosis and overtreatment. We describe the overdiagnosis and the prevalence of spirometrically defined false positive COPD, as well as their relationship with overtreatment across 23 population samples in 20 countries participating in the BOLD Study between 2003 and 2012.METHODS: A false positive diagnosis of COPD was considered when participants reported a doctor's diagnosis of COPD, but postbronchodilator spirometry was unobstructed (FEV1/FVC > LLN). Additional analyses were performed using the fixed ratio criterion (FEV1/FVC < 0.7).RESULTS: Among 16,177 participants, 919 (5.7%) reported a previous medical diagnosis of COPD. Postbronchodilator spirometry was unobstructed in 569 subjects (61.9%): false positive COPD. A similar rate of overdiagnosis was seen when using the fixed ratio criterion (55.3%). In a subgroup analysis excluding participants who reported a diagnosis of "chronic bronchitis" or "emphysema" (n = 220), 37.7% had no airflow limitation. The site-specific prevalence of false positive COPD varied greatly, from 1.9% in low- to middle-income countries to 4.9% in high-income countries. In multivariate analysis, overdiagnosis was more common among women, and was associated with higher education; former and current smoking; the presence of wheeze, cough, and phlegm; and concomitant medical diagnosis of asthma or heart disease. Among the subjects with false positive COPD, 45.7% reported current use of respiratory medication. Excluding patients with reported asthma, 34.4% of those with normal spirometry still used a respiratory medication.CONCLUSIONS: False positive COPD is frequent. This might expose nonobstructed subjects to possible adverse effects of respiratory medication.
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| 28. |
- Studnicka, Michael, et al.
(författare)
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COPD : Should Diagnosis Match Physiology?
- 2020
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Ingår i: Chest. - : Elsevier BV. - 0012-3692 .- 1931-3543. ; 157:2, s. 473-475
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 29. |
- Tobias, Peter, et al.
(författare)
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Electrical characterization of chemical sensors based on catalytic metal gate - Silicon carbide Schottky diodes
- 1998
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Ingår i: Silicon Carbide, III-Nitrides and Related Materials, Part 1-2. - : Trans Tech Publications. - 0878497900 ; , s. 1097-1100
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Konferensbidrag (refereegranskat)abstract
- The IV-characteristics of platinum gate Schottky diodes with an interfacial layer of TaSix or Ta depends on gas ambient and they are therefore used as gas sensors, e.g. for combustion engine monitoring. Ideality factors and barrier heights depend on interfacial layers and temperature and are further investigated here. Gas sensitive Schottky diodes on both p-and n-type SIC are shown.
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| 30. |
- Tobias, Peter, et al.
(författare)
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Studies of the ambient dependent inversion capacitance of catalytic metal oxide silicon carbide devices based on 6H- and 4H-SiC material
- 1998
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Ingår i: Silicon Carbide, III-Nitrides and Related Materials, Part 1-2. - : Trans Tech Publications. - 0878497900 ; , s. 1089-1092
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Konferensbidrag (refereegranskat)abstract
- Platinum-oxide-silicon carbide structures change their capacitance upon gas exposure and are used as gas sensors. The decrease of the inversion capacitance within 750 to 900 degrees C due to hydrogen exposure is studied for 4H- and 6H-SiC,:both n- and p-type. A mechanism for the capacitance decrease is suggested which explains also the large change in the conductance of the structures.
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| 31. |
- Unéus, Lars, et al.
(författare)
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Schottky diodes with thin catalytic gate metals for potential use as ammonia sensors for exhaust gases
- 1999
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Ingår i: Sensors and materials. - : Scientific Publishing Division Myu. - 0914-4935. ; 11:5, s. 305-318
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Tidskriftsartikel (refereegranskat)abstract
- Selective catalytic reduction (SCR) is a method in which ammonia reacts with nitric oxides in a catalytic converter to form water and nitrogen. We show that catalytic Metal Insulator Silicon Carbide (MISiC) devices can be used as ammonia sensors for a SCR system in a diesel engine. Different catalytic metals, Pt and Ir, with a thickness of 30 or 50 nm were investigated. The temperature dependence of the ammonia response of the sensors was characterized. Maximum responses were found at temperatures between 225-250 degrees C. Preliminary experiments were performed to investigate how annealing in different gas ambient influences the response-temperature curve of the sensors. In synthetic diesel exhausts with ammonia added, the sensors showed very good selectivity for ammonia and a small interaction effect with oxygen. The influence of other gas components was almost negligible. Temperature in the diesel exhaust system can reach 550 degrees C; however, operating at temperatures above 400 degrees C limited the lifetime of the sensor. Anger electron spectroscopy (AES) revealed that island formation of the metal due to structural changes was the main reason for failure of the sensor.
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