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1

Nano-Hydroxyapatite Thick Film Gas Sensors  

NASA Astrophysics Data System (ADS)

In the present work pure and metal ions (Co and Fe) doped hydroxyapatite (HAp) thick films have been successfully utilized to improve the structural, morphological and gas sensing properties. Nanocrystalline HAp powder is synthesized by wet chemical precipitation route, and ion exchange process is employed for addition of Co and Fe ions in HAp matrix. Moreover, swift heavy ion irradiation (SHI) technique is used to modify the surface of pure and metal ion exchanged HAp with various ion fluence. The structural investigation of pure and metal ion exchanged HAp thick films are carried out using X-ray diffraction and the presence of functional group is observed by means FTIR spectroscopy. Furthermore, surface morphology is visualized by means of SEM and AFM analysis. CO gas sensing study is carried out for, pure and metal ions doped, HAp thick films with detail investigation on operating temperature, response/recovery time and gas uptake capacity. The surface modifications of sensor matrix by SHI enhance the gas response, response/recovery and gas uptake capacity. The significant observation is here to note that, addition of Co and Fe in HAp matrix and surface modification by SHI improves the sensing properties of HAp films drastically resulting in gas sensing at relatively lower temperatures.

Khairnar, Rajendra S.; Mene, Ravindra U.; Munde, Shivaji G.; Mahabole, Megha P.

2011-12-01

2

Thin film metal oxide gas sensor array for gas detection  

NASA Astrophysics Data System (ADS)

This paper presents how an array of sensors with various sensitivities can be used for reliable detection and recognition of gases. An array of six different thin film metal oxide gas sensors has been constructed and tested. The selected sensors are based on indium, zinc, tin and titanium thin film oxides deposited by reactive magnetron sputtering. Sensors operate inside a measuring chamber at elevated temperatures of 250 - 300°C. The sensors responses upon hydrogen and ammonia exposure (0 - 3000 ppm) at relative humidity (0 - 75%Rh) are studied. The results show that exploiting the cross sensitivity and different sensing performance of the sensors allows to increase the reliability of gas sensing at relatively low operating temperatures.

Gwi?d?, Patryk; Brudnik, Andrzej; Zakrzewska, Katarzyna

2013-07-01

3

Ammonia gas sensor based on electrosynthesized polypyrrole films  

Microsoft Academic Search

In this work, design and fabrication of micro-gas-sensors, polymerization and deposition of poly(pyrrole) thin films as sensitive layer for the micro-gas-sensors by electrochemical processing, and characterization of the polymer films by FTIR, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), are reported. The change in conductance of thin polymer layers is used as a sensor signal. The behaviours, including

Stéphanie Carquigny; Jean-Baptiste Sanchez; Franck Berger; Boris Lakard; Fabrice Lallemand

2009-01-01

4

Recent developments in semiconducting thin-film gas sensors  

Microsoft Academic Search

A critical review of thin-film semiconducting materials that are used as gas sensors is presented in this paper. These materials can be approximately divided into two main groups: the first includes sensors that detect oxygen with variations of bulk or surface conductance; the second comprises all the materials that detect oxidizing and reducing gases in air at constant oxygen partial

G Sberveglieri

1995-01-01

5

Thin palladium film as a sensor of hydrogen gas dissolved in transformer oil  

Microsoft Academic Search

A sensor for the detection of hydrogen gas dissolved in the transformer oil is proposed. The absorption of hydrogen in thin palladium film causes changes in the electrical and optical properties of the film. The proposed structure can be simultaneously used as a resistance and optical sensor. The sensor has been tested for different hydrogen concentration and in different temperatures.

Jerzy Bodzenta; Bogus?aw Burak; Zbigniew Gacek; Wies?aw P. Jakubik; Stanis?aw Kochowski; Marian Urba?czyk

2002-01-01

6

Significance of microstructure for a MOCVD-grown YSZ thin film gas sensor  

SciTech Connect

The authors report the fabrication and characterization of a low temperature (200--400 C) thin film gas sensor constructed from a MOCVD-grown yttria-stabilized zirconia (YSZ) layer sandwiched between two platinum thin film electrodes. A reproducible gas-sensing response is produced by applying a cyclic voltage which generates voltammograms with gas-specific current peaks and shapes. Growth conditions are optimized for preparing YSZ films having dense microstructures, low leakage currents, and maximum ion conductivities. In particular, the effect of growth temperature on film morphology and texture is discussed and related to the electrical and gas-sensing properties of the thin film sensor device.

Vetrone, J.; Foster, C.; Bai, G. [Argonne National Lab., IL (United States). Material Science Div.

1996-11-01

7

Gold-carbon composite thin films for electrochemical gas sensor prepared by reactive plasma sputtering  

NASA Astrophysics Data System (ADS)

We have investigated the properties of gold-carbon composite thin films prepared by a plasma sputtering deposition using argon and methane mixture gas. These composite films have an uneven surface in submicron scale or consist of nano-scale particles of gold polycrystalline. Such morphological properties can be controlled by the sputtering voltage and the partial pressure of methane gas. The working electrode of electrochemical gas sensor has needed a stable gas sensitivity and a good gas selectivity. Our composite film is one of the excellent candidates for a thin film working electrode of electrochemical gas sensor. It is described that the output current of sensor is related to the preparation conditions of the thin films and increase linearly as the concentration of PH 3 gas ranging from 0.1 to 1.0 ppm is increasing.

Okamoto, A.; Suzuki, Y.; Yoshitake, M.; Ogawa, S.; Nakano, N.

1997-01-01

8

Heated thick-film titania exhaust gas oxygen sensors  

Microsoft Academic Search

This paper discusses laboratory propane burner and engine dynamometer durability testing of thick-film titania sensors whose resistance changes several orders of magnitude in response to changes in the partial pressure of oxygen around the stoichiometric point. Development has progressed to where porous titania films applied to alumina substrates exhibit switching and declay times equal to or faster than those achieved

J. L. Pfeifer; T. A. Libsch; H. P. Wertheimer

1984-01-01

9

Organic hydrogen gas sensor with palladium-coated ?-phase poly(vinylidene fluoride) thin films  

NASA Astrophysics Data System (ADS)

We have proposed an organic hydrogen gas sensor in which palladium (Pd)-coated ?-phase poly(vinylidene fluoride) (PVDF) films are utilized. Volume expansion of the Pd thin film caused by absorption of hydrogen gas is monitored by a piezoelectric thin film of PVDF attached to the Pd films. We have developed a simple method of synthesizing ?-phase PVDF films from ?-phase PVDF powder by using a wet process in which a mixture of acetone and hexamethylphosphoric triamide is used as the solvent for the PVDF powder. The sensor works by itself at room temperature without a power source.

Imai, Yuji; Kimura, Yasuo; Niwano, Michio

2012-10-01

10

Copper on-top-sputtering induced modification of tin dioxide thin film gas sensors  

Microsoft Academic Search

Thin film gas sensors based on pure tin dioxide were modified by sputtering of copper on the surface of the films. A gradual increase of an amount of the on-top-Cu produced increasing doping with uniform distribution of copper throughout entire tin oxide film. An increase of an amount of Cu caused continuous variation of the clean air resistance and the

A Galdikas; A Mironas; A Šetkus; W Göpel; K.-D Schierbaum

1999-01-01

11

Significance of microstructure for a MOCVD-grown YSZ thin film gas sensor.  

National Technical Information Service (NTIS)

The authors report the fabrication and characterization of a low temperature (200--400 C) thin film gas sensor constructed from a MOCVD-grown yttria-stabilized zirconia (YSZ) layer sandwiched between two platinum thin film electrodes. A reproducible gas-s...

J. Vetrone C. Foster G. Bai

1996-01-01

12

The Effects of Two Thick Film Deposition Methods on Tin Dioxide Gas Sensor Performance  

PubMed Central

This work demonstrates the variability in performance between SnO2 thick film gas sensors prepared using two types of film deposition methods. SnO2 powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes were investigated, and a new binder-less deposition procedure was developed and characterized. The binder recipes yielded sensors with poor film uniformity and poor structural integrity, compared to the binder-less deposition method. Sensor performance at a fixed operating temperature of 330 °C for the different film deposition methods was evaluated by exposure to 500 ppm of the target gas carbon monoxide. A consequence of the poor film structure, large variability and poor signal properties were observed with the sensors fabricated using binders. Specifically, the sensors created using the binder recipes yielded sensor responses that varied widely (e.g., S = 5 – 20), often with hysteresis in the sensor signal. Repeatable and high quality performance was observed for the sensors prepared using the binder-less dispersion-drop method with good sensor response upon exposure to 500 ppm CO (S = 4.0) at an operating temperature of 330 °C, low standard deviation to the sensor response (±0.35) and no signal hysteresis.

Bakrania, Smitesh D.; Wooldridge, Margaret S.

2009-01-01

13

Hydrogen gas sensor based on palladium and yttrium alloy ultrathin film.  

PubMed

Compared with the other hydrogen sensors, optical fiber hydrogen sensors based on thin films exhibits inherent safety, small volume, immunity to electromagnetic interference, and distributed remote sensing capability, but slower response characteristics. To improve response and recovery rate of the sensors, a novel reflection-type optical fiber hydrogen gas sensor with a 10 nm palladium and yttrium alloy thin film is fabricated. The alloy thin film shows a good hydrogen sensing property for hydrogen-containing atmosphere and a complete restorability for dry air at room temperature. The variation in response value of the sensor linearly increases with increased natural logarithm of hydrogen concentration (ln[H(2)]). The shortest response time and recovery response time to 4% hydrogen are 6 and 8 s, respectively. The hydrogen sensors based on Pd(0.91)Y(0.09) alloy ultrathin film have potential applications in hydrogen detection and measurement. PMID:23278019

Yi, Liu; You-Ping, Chen; Han, Song; Gang, Zhang

2012-12-01

14

High-temperature gas sensor using perovskite thin films on a suspended microheater  

NASA Astrophysics Data System (ADS)

Suspended microstructures consisting of a thin oxide/nitride diaphragm with embedded polysilicon heaters were designed and fabricated using a standard complementary metal-oxide-semiconductor process and simple postprocessing. Thin films of gas sensitive materials based on the SrFeO2.5+x nonstoichiometric perovskite family were deposited onto the diaphragms by room-temperature pulsed excimer laser deposition. Successful chemical sensor functionality was demonstrated. With applied power up to 30 mW, estimated temperatures of the gas sensor film up to 900 °C were reached. When the device was exposed to volatile organic compounds (VOCs) such as acetone and methanol, a reversible ten to 100-fold increase in sensor film resistance was observed, with response times from less than 1 s to a few minutes. Sensor response sensitivity depended on applied power and on the nature of the VOC analyte. This sensor device has the potential for use in multiarray configurations such as in an electronic nose.

Grudin, O.; Marinescu, R.; Landsberger, L. M.; Kahrizi, M.; Frolov, G.; Cheeke, J. D. N.; Chehab, S.; Post, M.; Tunney, J.; Du, X.; Yang, D.; Segall, D.

2002-05-01

15

Novel gas sensor using polymer-film-coated quartz resonator for environmental monitoring  

Microsoft Academic Search

The functional design of the smart electronic nose using polymer-film-coated quartz resonator gas sensors, based on the solubility parameter of sensing membrane and gases, is carried out in order to develop a sensor with excellent selectivity and high sensitivity for harmful gases such as toluene, acetaldehyde and ammonia gases. The polymer films such as propylene-butyl, polycarbonate and acrylic-resin of which

H Nanto; Y Yokoi; T Mukai; J Fujioka; E Kusano; A Kinbara; Y Douguchi

2000-01-01

16

Planar Zeolite Film-Based Potentiometric Gas Sensors Manufactured by a Combined Thick-Film and Electroplating Technique  

PubMed Central

Zeolites are promising materials in the field of gas sensors. In this technology-oriented paper, a planar setup for potentiometric hydrocarbon and hydrogen gas sensors using zeolites as ionic sodium conductors is presented, in which the Pt-loaded Na-ZSM-5 zeolite is applied using a thick-film technique between two interdigitated gold electrodes and one of them is selectively covered for the first time by an electroplated chromium oxide film. The influence of the sensor temperature, the type of hydrocarbons, the zeolite film thickness, and the chromium oxide film thickness is investigated. The influence of the zeolite on the sensor response is briefly discussed in the light of studies dealing with zeolites as selectivity-enhancing cover layers.

Marr, Isabella; Reiss, Sebastian; Hagen, Gunter; Moos, Ralf

2011-01-01

17

Micromachined thin film solid state electrochemical CO 2, NO 2 and SO 2 gas sensors  

Microsoft Academic Search

Among the many physical and chemical strategies used to make air pollution gas sensors for COx, NOx, SOx monitoring, those employing electrochemical detection means offer the highest selectivity, long lifetimes, low drift and low costs of manufacture. Targeting the three gases CO2, NO2 and SO2, new solid-electrolyte-based, selective potentiometric gas sensors were fabricated in both bulk and thin film versions.

J. F Currie; A Essalik; J-C Marusic

1999-01-01

18

Preparation of titanium dioxide films by sol-gel route for gas sensors  

Microsoft Academic Search

Semiconductor oxides such as SnO2, TiO2, WO3, ZnO2 etc. have been shown to be useful as gas sensor materials for monitoring various pollutant gases like H2S, NOx, NH3 etc. In this work, we would like to present the preparation of titanium dioxide films for gas sensor application, via the sol-gel technique. The coating solution was prepared by using titanium isopropoxide

Vasilica Schiopu; Alina Matei; Ileana Cernica; Cecilia Podaru

2009-01-01

19

Classification of chemical warfare agents using thick film gas sensor array  

Microsoft Academic Search

Semiconductor thick film gas sensors based on tin oxide are fabricated and their gas response characteristics are examined for four simulant gases of chemical warfare agent (CWA)s. The sensing materials are prepared in three different sets such as impregnation, physical mixing (ball-milling) and co-precipitation method. Surface morphology, particle size, and specific surface area of fabricated sensing films are performed by

Nak-Jin Choi; Jun-Hyuk Kwak; Yeon-Tae Lim; Tae-Hyun Bahn; Ky-Yeol Yun; Jae-Chang Kim; Jeung-Soo Huh; Duk-Dong Lee

2005-01-01

20

Quartz crystal microbalance (QCM) sensor for CH 3SH gas by using polyelectrolyte-coated sol–gel film  

Microsoft Academic Search

A new structure of sensing film for QCM sensor electrode was investigated. Gas-sensing device for toxic gases requires high sensor sensitivity and quick response. Increasing the surface area of sensing film was effective to improve the sensor sensitivity and response speed of QCM sensors, however it is difficult to increase the surface area of polymeric film. In this paper, Al2O3

Masashi Kikuchi; Seimei Shiratori

2005-01-01

21

Elaboration of ammonia gas sensors based on electrodeposited polypyrrole--cobalt phthalocyanine hybrid films.  

PubMed

The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix. PMID:24209308

Patois, Tilia; Sanchez, Jean-Baptiste; Berger, Franck; Fievet, Patrick; Segut, Olivier; Moutarlier, Virginie; Bouvet, Marcel; Lakard, Boris

2013-12-15

22

A compact wireless gas sensor using a?carbon nanotube\\/PMMA thin film chemiresistor  

Microsoft Academic Search

The design and development of a compact wireless gas sensor with a surface modified multiwalled carbon nanotube (f-CNT) chemiresistor as the sensing element is presented in this paper. f-CNT\\/polymer composite sensing film is patterned on a printed circuit board and is integrated to the wireless system. The change in resistance of the CNT\\/polymer composite film due to exposure of different

Jose K Abraham; Biju Philip; Ashwin Witchurch; Vijay K Varadan; C Channa Reddy

2004-01-01

23

NiO \\/ Fe 2O 3 polymer thick films as room temperature gas sensors  

Microsoft Academic Search

This work investigates the use of NiO\\/Fe2O3 as a room temperature (RT) polymer thick film gas sensor. To find the optimum ratio of NiO to Fe2O3, three compositions were prepared using different molecular percentages (75\\/25, 50\\/50 and 25\\/75 M wt.%) and prepared as a thick film paste. These pastes were then screen-printed onto glass substrates with interdigitated silver (Ag) electrodes.

K. Arshak; I. Gaidan

2006-01-01

24

Nanocrystalline SnO2:F Thin Films for Liquid Petroleum Gas Sensors  

PubMed Central

This paper reports the improvement in the sensing performance of nanocrystalline SnO2-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO2 films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO2 with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO2:F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO2 was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO2:F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection.

Chaisitsak, Sutichai

2011-01-01

25

Nanocrystalline SnO2:F thin films for liquid petroleum gas sensors.  

PubMed

This paper reports the improvement in the sensing performance of nanocrystalline SnO(2)-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO(2) films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO(2) with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO(2):F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO(2) was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO(2):F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection. PMID:22164007

Chaisitsak, Sutichai

2011-01-01

26

Preparation of titanium dioxide films by sol-gel route for gas sensors  

NASA Astrophysics Data System (ADS)

Semiconductor oxides such as SnO2, TiO2, WO3, ZnO2 etc. have been shown to be useful as gas sensor materials for monitoring various pollutant gases like H2S, NOx, NH3 etc. In this work, we would like to present the preparation of titanium dioxide films for gas sensor application, via the sol-gel technique. The coating solution was prepared by using titanium isopropoxide precursor, which was hydrolyzed with distilled water under the catalytic effect of different acids (HNO3, HCl or CH3COOH). Titanium dioxide films have been deposited using spin coating method and then synthesized at different temperatures. Fourier transform infrared spectroscopy observation has been used to analyze the sol-gel process. The morphology and the structure of the thin films were analyzed.

Schiopu, Vasilica; Matei, Alina; Cernica, Ileana; Podaru, Cecilia

2009-01-01

27

Novel BN/Pd composite films for stable liquid petroleum gas sensor  

NASA Astrophysics Data System (ADS)

Composite films of BN/Pd were synthesized by depositing thin films of BN by pulsed laser deposition technique and evaporating a thin layer of palladium on top of it to form a bi-layer structure. This bi-layer structure was then subjected to rapid thermal annealing for the incorporation of Pd in BN. The films thus obtained were characterized by SEM, XRD and FTIR studies. Liquid petroleum gas (LPG) sensing properties were also investigated critically. Very stable and reproducible LPG sensing properties and comparatively at lower operating temperature of 460 K would make this material superior to prevalent oxide based sensors.

Ghosh, D.; Ghosh, B.; Hussain, S.; Chaudhuri, Subhajyoti; Bhar, R.; Pal, A. K.

2012-12-01

28

Gas-sensor properties of SnO 2 films implanted with gold and iron ions  

Microsoft Academic Search

SnO2 gas-sensor films were modified by implantation of gold and iron ions. The change in electrical resistivity of the films caused\\u000a by inflammable gases, H2, CO, CH4 and C2H5OH, was measured in the temperature range 100–500C, and compared to non-implanted films. The morphological changes caused\\u000a by gold and iron ion implantation were also investigated by atomic force microscopy. After ion

K. NOMURA; H. SHIOZAWA; T. TAKADA; H REUTHER; E RICHTER

1997-01-01

29

The effects of thickness and operation temperature on ZnO:Al thin film CO gas sensor  

Microsoft Academic Search

Al-doped ZnO films were deposited onto SiO2\\/Si substrates by rf magnetron sputtering system as a CO gas sensor. The dependence of the thin film thickness on CO gas sensing properties was investigated, where the film thickness was varied by controlling the deposition time. The structure of the deposited ZnO:Al films was determined by X-ray diffraction, scanning electron microscopy and atomic

J. F. Chang; H. H. Kuo; I. C. Leu; M. H. Hon

2002-01-01

30

Influence of the Phase Composition on the Electrical Conductivity of Gas Sensors Based on Antimony-Doped Tin Dioxide Films  

Microsoft Academic Search

Scanning electron microscopy is used to examine the structure (of thin- and thick-film gas sensors based on Sn1-xSbxO2 solid solutions. The solid-solution particles are found not to sinter. The temperature dependences of the resistance and the volt-ampere characteristics of the films are studied. A mechanism for the gas sensitivity of the films to gas is suggested. In the model presented

2001-01-01

31

Gas sensitivity of ZnO based thick film sensor to NH 3 at room temperature  

Microsoft Academic Search

Calcined powders of pure and doped ZnO have been prepared and characterized by XRD and scanning electron microscopy (SEM). Employing these powders ZnO, Pd–ZnO, Fe–ZnO and Ru–ZnO thick film sensor elements have been prepared and tested for specific sensitivity to ammonia gas in air at room temperature. Among all, Pd–ZnO showed high sensitivity to ammonia in the range 50–90 ppm

G. S. Trivikrama Rao; D Tarakarama Rao

1999-01-01

32

Nanostructured zinc oxide films synthesized by successive chemical solution deposition for gas sensor applications  

SciTech Connect

Nanostructured ZnO thin films have been deposited using a successive chemical solution deposition method. The structural, morphological, electrical and sensing properties of the films were studied for different concentrations of Al-dopant and were analyzed as a function of rapid photothermal processing temperatures. The films were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron and micro-Raman spectroscopy. Electrical and gas sensitivity measurements were conducted as well. The average grain size is 240 and 224 A for undoped ZnO and Al-doped ZnO films, respectively. We demonstrate that rapid photothermal processing is an efficient method for improving the quality of nanostructured ZnO films. Nanostructured ZnO films doped with Al showed a higher sensitivity to carbon dioxide than undoped ZnO films. The correlations between material compositions, microstructures of the films and the properties of the gas sensors are discussed.

Lupan, O. [Department of Microelectronics and Semiconductor Devices, Technical University of Moldova, 168 Stefan cel Mare Blvd., MD-2004 Chisinau (Moldova, Republic of); Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816-2385 (United States)], E-mail: lupanoleg@yahoo.com; Chow, L. [Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816-2385 (United States); Shishiyanu, S. [Department of Microelectronics and Semiconductor Devices, Technical University of Moldova, 168 Stefan cel Mare Blvd., MD-2004 Chisinau (Moldova, Republic of); Monaico, E. [National Center for Materials Study and Testing, Technical University of Moldova, 168 Stefan cel Mare Blvd., MD-2004 Chisinau (Moldova, Republic of); Shishiyanu, T.; Sontea, V. [Department of Microelectronics and Semiconductor Devices, Technical University of Moldova, 168 Stefan cel Mare Blvd., MD-2004 Chisinau (Moldova, Republic of); Roldan Cuenya, B.; Naitabdi, A.; Park, S.; Schulte, A. [Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816-2385 (United States)

2009-01-08

33

Flexible room-temperature NO2 gas sensors based on carbon nanotubes\\/reduced graphene hybrid films  

Microsoft Academic Search

We present a flexible room temperature NO2 gas sensor consisting of vertical carbon nanotubes (CNTs)\\/reduced graphene hybrid film supported by a polyimide substrate. The reduced graphene film alone showed a negligible sensor response, exhibiting abnormal N-P transitions during the initial NO2 injection. A hybrid film, formed by the growth of a vertically aligned CNT array (with CNTs 20 mum in

Hu Young Jeong; Dae-Sik Lee; Hong Kyw Choi; Duck Hyun Lee; Ji-Eun Kim; Jeong Yong Lee; Won Jong Lee; Sang Ouk Kim; Sung-Yool Choi

2010-01-01

34

Low temperature deposition of silver sulfide thin films by AACVD for gas sensor application  

NASA Astrophysics Data System (ADS)

Crack free Ag2S thin films were deposited on glass substrates by aerosol assisted chemical vapor deposition (AACVD) using [Ag(S2CN (C2H5)2)3]2 (1) as a precursor. Thin films were deposited from solution of methanol at 400 °C and characterized by X-ray diffraction (XRD), UV-vis spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. SEM image of thin film showed well-defined and porous surface morphology with an average particle size of 0.3-0.5 ?m. Optical band gaps energy of 1.33 eV was estimated for Ag2S thin film, by extrapolating the linear part of the Tauc plot recorded at room temperature. The gas sensing characteristics of the novel gas sensors based on Ag2S were investigated for the detection carbon monoxide. The effect of operating temperature and change in gas concentration on the performance of carbon monoxide were investigated. The sensing mechanism of sensor was discussed.

Hussain, Syed Tajammul; Bakar, Shahzad Abu; Saima, BiBi; Muhammad, Bakhtiar

2012-10-01

35

Nanoparticle thin films for gas sensors prepared by matrix assisted pulsed laser evaporation.  

PubMed

The matrix assisted pulsed laser evaporation (MAPLE) technique has been used for the deposition of metal dioxide (TiO(2), SnO(2)) nanoparticle thin films for gas sensor applications. For this purpose, colloidal metal dioxide nanoparticles were diluted in volatile solvents, the solution was frozen at the liquid nitrogen temperature and irradiated with a pulsed excimer laser. The dioxide nanoparticles were deposited on Si and Al(2)O(3) substrates. A rather uniform distribution of TiO(2) nanoparticles with an average size of about 10 nm and of SnO(2) nanoparticles with an average size of about 3 nm was obtained, as demonstrated by high resolution scanning electron microscopy (SEM-FEG) inspections. Gas-sensing devices based on the resistive transduction mechanism were fabricated by depositing the nanoparticle thin films onto suitable rough alumina substrates equipped with interdigitated electrical contacts and heating elements. Electrical characterization measurements were carried out in controlled environment. The results of the gas-sensing tests towards low concentrations of ethanol and acetone vapors are reported. Typical gas sensor parameters (gas responses, response/recovery time, sensitivity, and low detection limit) towards ethanol and acetone are presented. PMID:22574039

Caricato, Anna Paola; Luches, Armando; Rella, Roberto

2009-01-01

36

Nanoparticle Thin Films for Gas Sensors Prepared by Matrix Assisted Pulsed Laser Evaporation  

PubMed Central

The matrix assisted pulsed laser evaporation (MAPLE) technique has been used for the deposition of metal dioxide (TiO2, SnO2) nanoparticle thin films for gas sensor applications. For this purpose, colloidal metal dioxide nanoparticles were diluted in volatile solvents, the solution was frozen at the liquid nitrogen temperature and irradiated with a pulsed excimer laser. The dioxide nanoparticles were deposited on Si and Al2O3 substrates. A rather uniform distribution of TiO2 nanoparticles with an average size of about 10 nm and of SnO2 nanoparticles with an average size of about 3 nm was obtained, as demonstrated by high resolution scanning electron microscopy (SEM-FEG) inspections. Gas-sensing devices based on the resistive transduction mechanism were fabricated by depositing the nanoparticle thin films onto suitable rough alumina substrates equipped with interdigitated electrical contacts and heating elements. Electrical characterization measurements were carried out in controlled environment. The results of the gas-sensing tests towards low concentrations of ethanol and acetone vapors are reported. Typical gas sensor parameters (gas responses, response/recovery time, sensitivity, and low detection limit) towards ethanol and acetone are presented.

Caricato, Anna Paola; Luches, Armando; Rella, Roberto

2009-01-01

37

Thin film temperature sensor  

NASA Technical Reports Server (NTRS)

Thin film surface temperature sensors were developed. The sensors were made of platinum-platinum/10 percent rhodium thermocouples with associated thin film-to-lead wire connections and sputtered on aluminum oxide coated simulated turbine blades for testing. Tests included exposure to vibration, low velocity hydrocarbon hot gas flow to 1250 K, and furnace calibrations. Thermal electromotive force was typically two percent below standard type S thermocouples. Mean time to failure was 42 hours at a hot gas flow temperature of 1250 K and an average of 15 cycles to room temperature. Failures were mainly due to separation of the platinum thin film from the aluminum oxide surface. Several techniques to improve the adhesion of the platinum are discussed.

Grant, H. P.; Przybyszewski, J. S.

1980-01-01

38

Optical fiber gas sensors based on hydrophobic alumina thin films formed by the electrostatic self-assembly monolayer process  

Microsoft Academic Search

Optical fiber gas sensors have been fabricated by deposition of Al2O3 and polymer ultra-thin films on the ends of optical fibers using the electrostatic self assembly monolayer process. These sensors are designed to operate at the standard transmission wavelengths with no cross sensitivity to temperature from at least 10 to 70°C. Experimental results of the response of these sensors to

Francisco J. Arregui; Ignacio R. Matías; Richard O. Claus

2003-01-01

39

Micro-machined thin film hydrogen gas sensor, and method of making and using the same  

NASA Technical Reports Server (NTRS)

A hydrogen sensor including a thin film sensor element formed, e.g., by metalorganic chemical vapor deposition (MOCVD) or physical vapor deposition (PVD), on a microhotplate structure. The thin film sensor element includes a film of a hydrogen-interactive metal film that reversibly interacts with hydrogen to provide a correspondingly altered response characteristic, such as optical transmissivity, electrical conductance, electrical resistance, electrical capacitance, magnetoresistance, photoconductivity, etc., relative to the response characteristic of the film in the absence of hydrogen. The hydrogen-interactive metal film may be overcoated with a thin film hydrogen-permeable barrier layer to protect the hydrogen-interactive film from deleterious interaction with non-hydrogen species. The hydrogen sensor of the invention may be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently configured as a hand-held apparatus.

DiMeo, Jr., Frank (Inventor); Bhandari, Gautam (Inventor)

2001-01-01

40

Patterning of thin tin oxide film with nano-size particle for two-dimensional micro-gas sensor array  

Microsoft Academic Search

Thin tin oxide film with nano-size particle was prepared on silicon substrate by hydrothermal synthetic method and successive sol–gel spin coating method. The fabrication method of tin oxide film with ultrafine nano-size crystalline structure was tried to be applied to fabrication of micro-gas sensor array on silicon substrate. The tin oxide film on silicon substrate was well patterned by chemical

Wan-Young Chung; Jun-Woo Lim

2003-01-01

41

Thin film hydrogen sensor  

DOEpatents

A hydrogen sensor element comprises an essentially inert, electrically-insulating substrate having a thin-film metallization deposited thereon which forms at least two resistors on the substrate. The metallization comprises a layer of Pd or a Pd alloy for sensing hydrogen and an underlying intermediate metal layer for providing enhanced adhesion of the metallization to the substrate. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors, and at least one of the resistors is left uncovered. The difference in electrical resistances of the covered resistor and the uncovered resistor is related to hydrogen concentration in a gas to which the sensor element is exposed.

Lauf, Robert J. (Oak Ridge, TN) [Oak Ridge, TN; Hoffheins, Barbara S. (Knoxville, TN) [Knoxville, TN; Fleming, Pamela H. (Oak Ridge, TN) [Oak Ridge, TN

1994-01-01

42

Manganese doped Zinc oxide thin film hydrogen gas sensor at reduced operating temperature  

Microsoft Academic Search

During the pas t few decades, semiconductor metal oxide (SMO) gas sensors have become a prime technology in several domestic, commercial, and industrial gas sensing. The semiconductor properties of zinc oxide along with its dopant remain to be trapped fully in its application as gas sensor. With the advent of nanotechnology, miniaturization and high sensitivity happens to be a key

Anjali Chatterjee; Partha Bhattacharjee; P. kumbakar; Nirmal Kumar Roy

2011-01-01

43

Flexible room-temperature NO2 gas sensors based on carbon nanotubes/reduced graphene hybrid films  

NASA Astrophysics Data System (ADS)

We present a flexible room temperature NO2 gas sensor consisting of vertical carbon nanotubes (CNTs)/reduced graphene hybrid film supported by a polyimide substrate. The reduced graphene film alone showed a negligible sensor response, exhibiting abnormal N-P transitions during the initial NO2 injection. A hybrid film, formed by the growth of a vertically aligned CNT array (with CNTs 20 ?m in length) on the reduced graphene film surface, exhibited remarkably enhanced sensitivities with weak N-P transitions. The increase in sensitivity was mainly attributed to the high sensitivity of the CNT arrays. The outstanding flexibility of the reduced graphene films ensured stable sensing performances in devices submitted to extreme bending stress.

Jeong, Hu Young; Lee, Dae-Sik; Choi, Hong Kyw; Lee, Duck Hyun; Kim, Ji-Eun; Lee, Jeong Yong; Lee, Won Jong; Kim, Sang Ouk; Choi, Sung-Yool

2010-05-01

44

Infrared emission spectroscopic study of the adsorption of oxygen on gas sensors based on polycrystalline metal oxide films  

Microsoft Academic Search

Infrared emission spectroscopy (IRES) was used for studying in situ gas-surface interactions and adsorbed species on semiconducting metal oxides based gas sensors under working conditions. Regarding the key position of oxygen for the surface chemistry of oxides, the adsorption and reaction of oxygen was studied on screen printed films of polycrystalline WO3, AlVO4 and Co3O4 in the temperature range between

R. Pohle; M. Fleischer; H. Meixner

2001-01-01

45

Fiber optic ammonia gas sensor utilizing surface plasmon resonance of copper/bromocresol purple thin films  

NASA Astrophysics Data System (ADS)

We present an experimental study of fiber optic ammonia gas sensor based on the phenomena of surface plasmon resonance working on wavelength modulation scheme. The principle of the sensor is based on the change in dielectric constant of the bromocresol purple (BCP) in the presence of ammonia gas. The sensor works at room temperature. Two different kinds of coating configurations have been considered, namely copper + BCP and silver + BCP, on the unclad portion of the fiber. The experiments have been carried out at the low concentrations (1 ppm - 10 ppm) of ammonia gas around the probe. The sensor with copper and BCP layers has greater sensitivity than sensor with silver and BCP layers. The proposed sensor has small response and recovery times.

Mishra, Satyendra K.; Bhardwaj, Shivani; Gupta, Banshi D.

2013-05-01

46

SnO2/Pt thin film laser ablated gas sensor array.  

PubMed

A gas sensor array was developed in a 10 × 10 mm(2) space using Screen Printing and Pulse Laser Ablation Deposition (PLAD) techniques. Heater, electrode, and an insulator interlayer were printed using the screen printing method on an alumina substrate, while tin oxide and platinum films, as sensing and catalyst layers, were deposited on the electrode at room temperature using the PLAD method, respectively. To ablate SnO(2) and Pt targets, depositions were achieved by using a 1,064 nm Nd-YAG laser, with a power of 0.7 J/s, at different deposition times of 2, 5 and 10 min, in an atmosphere containing 0.04 mbar (4 kPa) of O(2). A range of spectroscopic diffraction and real space imaging techniques, SEM, EDX, XRD, and AFM were used in order to characterize the surface morphology, structure, and composition of the films. Measurement on the array shows sensitivity to some solvent and wood smoke can be achieved with short response and recovery times. PMID:22164041

Shahrokh Abadi, Mohammad Hadi; Hamidon, Mohd Nizar; Shaari, Abdul Halim; Abdullah, Norhafizah; Wagiran, Rahman

2011-01-01

47

Thin film hydrogen sensor  

DOEpatents

A hydrogen sensor element comprises an essentially inert, electrically-insulating substrate having a thin-film metallization deposited thereon which forms at least two resistors on the substrate. The metallization comprises a layer of Pd or a Pd alloy for sensing hydrogen and an underlying intermediate metal layer for providing enhanced adhesion of the metallization to the substrate. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors, and at least one of the resistors is left uncovered. The difference in electrical resistances of the covered resistor and the uncovered resistor is related to hydrogen concentration in a gas to which the sensor element is exposed. 6 figs.

Lauf, R.J.; Hoffheins, B.S.; Fleming, P.H.

1994-11-22

48

Enhancement in sensitivity of copper sulfide thin film ammonia gas sensor: Effect of swift heavy ion irradiation  

SciTech Connect

The studies are carried out on the effect of swift heavy ion (SHI) irradiation on surface morphology and electrical properties of copper sulfide (Cu{sub x}S) thin films with three different chemical compositions (x values). The irradiation experiments have been carried out on Cu{sub x}S films with x=1.4, 1.8, and 2 by 100 MeV gold heavy ions at room temperature. These as-deposited and irradiated thin films have been used to detect ammonia gas at room temperature (300 K). The SHI irradiation treatment on x=1.4 and 1.8 copper sulfide films enhances the sensitivity of the gas sensor. The results are discussed considering high electronic energy deposition by 100 MeV gold heavy ions in a matrix of copper sulfide.

Sagade, Abhay Abhimanyu [Department of Physics, Thin Film and Nanotechnology Laboratory, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, 431004 Maharashtra (India); Sharma, Ramphal [Department of Physics, Thin Film and Nanotechnology Laboratory, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, 431004 Maharashtra (India); Department of Chemistry, Hanyang University, Sungdong-Ku, Haengdang-dong 17, Seoul 133-791 (Korea, Republic of); Sulaniya, Indra [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, P.O. Box 10502, New Delhi 110067 (India)

2009-02-15

49

Design of low cost gas sensor based on SrTiO3 and BaTiO3 films.  

PubMed

We have prepared SrTiO3/BaTiO3 multilayer film on alumina substrates by a sol-gel technique and investigated their response for sensing ethanol vapor. The surface morphology of the films were characterized by atomic force microscope (AFM) showing that the grain size of the films increase up to 40 nm as the annealing temperature increased to 1000 degrees C. The ethanol sensors based on SrTiO3/BaTiO3 thin films were fabricated by applying interdigitated gold electrodes by sputtering technique. The ethanol sensing characteristics of SrTiO3/BaTiO3 thin films were quantified by the change in resistance of the sensors when they were exposed to ethanol. The optimum operating tempearature of these sensors was found to be 350 degrees C. In addition, the film annealed at 1000 degrees C exhibited p-type gas sensing behavior with the best sensitivity of 30-100 for low ethanol concentration in the range of 100-1000 ppm. PMID:21137905

Hodak, Satreerat K; Supasai, Thidarat; Wisitsoraat, Anurat; Hodak, Jose H

2010-11-01

50

Nitrogen dioxide gas sensors based on titanium dioxide thin films deposited on langasite  

Microsoft Academic Search

Conductometric sensors, based on pure and Au-doped TiO2 thin films on langasite (LGS) substrates have been investigated for detecting low concentrations (510 ppb and 1060 ppb) of NO2 in synthetic air at a temperature range between 220 °C and 320 °C. Thin films of TiO2 were deposited using the radio frequency (RF) magnetron sputtering method. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques

Joy Tan; Wojtek Wlodarski; Kourosh Kalantar-Zadeh

2007-01-01

51

F-doped nanocrystalline SnO2 thin films for liquid petroleum gas (LPG) sensors  

Microsoft Academic Search

In this paper we reported the improvement sensing performance of nanocrystalline SnO2 thin film based LPG sensors by doping with fluorine. Un-doped and F-doped tin oxide films were prepared on glass substrates by dip-coating technique using a layer-by-layer deposition cycle (alternating between dip- coating a thin layer followed by a drying in air after each new layer). The results showed

S. Chaisitsak

2011-01-01

52

Indium Tin Oxide thin film gas sensors for detection of ethanol vapours  

Microsoft Academic Search

Indium Tin Oxide (ITO: In2O3+17% SnO2) thin films grown on alumina substrate at 648 K temperatures using direct evaporation method with two gold pads deposited on the top for electrical contacts were exposed to ethanol vapours (200–2500 ppm). The operating temperature of the sensor was optimized. The sensitivity variation of films having different thickness was studied. The sensitivity of the

V. S. Vaishnav; P. D. Patel; N. G. Patel

2005-01-01

53

Conductivity model for sputtered ZnO-thin film gas sensors  

Microsoft Academic Search

The electrical properties of reactively sputtered ZnO thin films used for chemical sensors are investigated in N2 and oxidizing atmosphere by Hall measurements. The measured carrier concentration and mobility of the polycrystalline ZnO films are well described by combining compensated electron conduction within the crystallites and thermionic emission of carriers across the grain boundaries. Results of a computer simulation are

K.-S. Weißenrieder; J. Muller

1997-01-01

54

Study on Ni-doped ZnO films as gas sensors  

NASA Astrophysics Data System (ADS)

Ni doped ZnO films were obtained by spin coating, using zinc acetate and nickel acetate as starting materials and N,N-dimethylformamide as solvent. The X-ray diffraction (XRD) analysis indicates that, spin coated films posses a polycrystalline structure. Ni doped ZnO films are single phase and no trace of nickel metal or binary zinc nickel phases are observed. The values of some structural parameters (crystallite size, surface roughness) are varying with the variation of Ni concentration. The sensitivity of Ni:ZnO films, at three different gasses (ammonia, liquefied petroleum gas and ethanol) was investigated. Obtained results indicate that our films are most sensitive to ammonia, the operating temperature was found to be 190 °C and the response time is 35 s. The gas sensitivity was found to depend on the Ni concentration in ZnO films.

Rambu, A. P.; Ursu, L.; Iftimie, N.; Nica, V.; Dobromir, M.; Iacomi, F.

2013-09-01

55

Amorphous Pb(Zr, Ti)O 3 thin film hydrogen gas sensor  

Microsoft Academic Search

The capacitive Pd\\/lead zirconate titanate (PZT)\\/Pt devices have been fabricated with amorphous Pb(Zrx, Ti1?x)O3 (x=0, 30, 53, 65, 90) thin films deposited using the sol–gel spin-coating technology. The PZT films have been characterized by TGA, DTA, X-ray diffraction (XRD), dielectric and electrical properties, and gas sensitivity measurement. It has been shown that the amorphous PZT film can be operative as

J Deng; W Zhu; O. K Tan; X Yao

2001-01-01

56

Comparison study of SnO 2 thin- and thick-film gas sensors  

Microsoft Academic Search

Polycrystalline SnO2 thin films were prepared at 600°C by metal organic chemical vapor deposition (MOCVD) technique using tetraethyltin as an organometallic (OM) source and UHP O2 as oxidant. The films were analyzed by means of XRD, SEM, and AES for their microstructure characterization and subjected to H2 and CO gas detection. The results were compared to SnO2 thick-films derived from

Sang Woo Lee; Ping Ping Tsai; Haydn Chen

2000-01-01

57

Gas identification by modulating temperatures of SnO 2-based thick film sensors  

Microsoft Academic Search

A new method is presented to identify the presence of two gases in the ambient atmosphere. The method employs only one SnO2-based gas sensor in a sinusoidal temperature mode to perform the quantitative analysis of a binary gas mixture (CO\\/NO2) in air.

A. Heilig; N. Bârsan; U. Weimar; M. Schweizer-Berberich; J. W. Gardner; W. Göpel

1997-01-01

58

Dual SAW sensor technique for determining mass and modulus changes in thin silicate films during gas adsorption  

SciTech Connect

Surface acoustic wave (SAW) sensors, which are sensitive to a variety of surface changes, have been widely used for chemical and physical sensing. The ability to control or compensate for the many surface forces has been instrumental in collecting valid data. In cases where it is not possible to neglect certain effects, such as frequency drift with temperature, methods such as the dual sensor technique have been utilized. This paper describes a novel use of a dual sensor technique, using two sensor materials, Quartz and GaAs, to separate out the contributions of mass and modulus of the frequency change during gas adsorption experiments. The large modulus change in the film calculated using this technique, and predicted by the Gassmann equation, provide a greater understanding of the challenges of SAW sensing.

Hietala, S.L.; Hietala, V.M.; Brinker, C.J.

2000-01-10

59

Development of a gas sensor by thick film technology for automotive applications: choice of materials—realization of a prototype  

Microsoft Academic Search

As a part of our research on new gas sensors, an original potentiometric gas sensor was developed. The gas sensor consists of a solid electrolyte associated with two different electrodes located in the same gas mixture. Owing to the interesting behavior of this sensor to the action of CO and NOx, it was decided to develop this device within the

N Guillet; R Lalauze; J.-P Viricelle; C Pijolat; L Montanaro

2002-01-01

60

O2 plasma-functionalized SWCNTs and PEDOT/PSS composite film assembled by dielectrophoresis for ultrasensitive trimethylamine gas sensor.  

PubMed

A novel gas sensor based on composite films of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) and single-walled carbon nanotubes (SWCNTs) was fabricated for the detection of fishy trimethylamine (TMA) vapor. The SWCNTs were functionalized by O2 plasma treatment to improve their solubility in the polymeric matrix, and alternative current dielectrophoresis was utilized for the first time to assemble the PEDOT/PSS-SWCNTs composite film to enhance the response to TMA molecules. The high resolution transmission electron microscopy (HR-TEM) images showed that the SWCNTs maintained their bulk structure after O2 plasma functionalization. The scanning electron microscopy (SEM) images of the composite film showed that the oxidized SWCNTs were orderly arranged and uniformly dispersed into the polymer by dielectrophoresis. Compositional analyses of SWCNTs by X-ray photoelectron spectroscopy (XPS) suggested that O2 plasma functionalization could remove amorphous carbon from the nanotube surface and introduce more hydrophilic oxygen-containing groups, leading to the improvement of SWCNTs solubility in the polymeric matrix. Gas sensitivities of the composite films largely relied on the treatment conditions. Compared to the raw or acid-treated SWCNTs-doped composite films, the film doped with SWCNTs modified by O2 plasma at 30 W for 3 min exhibited the most sensitive and stable response characteristics to ppb-level TMA gas. PMID:23862176

Guo, Xishan; Jian, Jinming; Lin, Liwei; Zhu, Hanyu; Zhu, Songming

2013-09-21

61

Resistance noise in TiO2-based thin film gas sensors under ultraviolet irradiation  

NASA Astrophysics Data System (ADS)

Resistance fluctuations in thin crystalline TiO2films were investigated for gas sensing applications. The measurements were carried out as the films were irradiated by ultraviolet (UV) light with a wavelength of 370 nm in the presence of H2S. The films were prepared by reactive DC magnetron sputtering. They had a crystalline phase of anatase and a mean grain size of 17.8 nm, as found by X-ray diffraction. A prominent change in resistance noise level was discovered as the irradiated film was exposed to a gas containing 1.5 ppm of H2S, while no change was observed in the absence of UV. This effect is possibly due to decomposition of the adsorbed gas, via photocatalysis induced by TiO2, or to a decrease of the potential barrier between the charged grains.

Topalian, Z.; Smulko, J. M.; Niklasson, G. A.; Granqvist, C. G.

2007-07-01

62

Nanoparticle metal-oxide films for micro-hotplate-based gas sensor systems  

Microsoft Academic Search

We report on the use of either reactive magnetron sputtering or screen printing to deposit tin and tungsten-oxide gas-sensitive layers onto integrated micromachined arrays. The procedures allow the deposition of the sensing layers before membranes have been etched, which leads to gas microsensors with an excellent fabrication yield. The microstructure of the sensitive films is analyzed by means of SEM

Peter Ivanov; Mariana Stankova; Eduard Llobet; Xavier Vilanova; Jesús Brezmes; Isabel Gràcia; Carles Cané; Josep Calderer; Xavier Correig

2005-01-01

63

ZnO:Al Thin Film Gas Sensor for Detection of Ethanol Vapor  

PubMed Central

The ZnO:Al thin films were prepared by RF magnetron sputtering on Si substrate using Pt as interdigitated electrodes. The structure was characterized by XRD and SEM analyses, and the ethanol vapor gas sensing as well as electrical properties have been investigated and discussed. The gas sensing results show that the sensitivity for detecting 400 ppm ethanol vapor was ?20 at an operating temperature of 250°C. The high sensitivity, fast recovery, and reliability suggest that ZnO:Al thin film prepared by RF magnetron sputtering can be used for ethanol vapor gas sensing.

Chou, Shih Min; Teoh, Lay Gaik; Lai, Wei Hao; Su, Yen Hsun; Hon, Min Hsiung

2006-01-01

64

Investigation on the Hydrogen Gas Sensor Based on Exothermicity Reaction by Hydrogen Absorption into the Pd Film  

NASA Astrophysics Data System (ADS)

We have proposed a novel micro-calorimetric hydrogen sensor based on the temperature difference detection due to the exothermic reaction caused by hydrogen absorption in the palladium (Pd) thin film as a hydrogen absorbing material, and demonstrated using the prototype hydrogen sensor with a microheater and a pair of cantilever SOI thermocouples that this H2 sensor by this proposed mechanism is surely possible. We have ascertained that the sensor output voltage is increased as the H2 concentration is increased, that the exothermic reaction ceases after finish of the hydrogen absorption, the exothermic reaction by hydrogen absorption occurs even in pure N2 gas, that larger output voltage is observed for lower ambient temperature even under no oxygen gas, and that this hydrogen sensor does not respond to the CH4 gas. We have found that the detection of H2 concentration based on the exothermic reaction is preferred to carried out after heating the sensing region rather than during heating it especially in lower H2 concentration than about 5 vol.%, because we can use the null method to detect the extremely low H2 concentration.

Takashima, Noriaki; Kimura, Mitsuteru

65

Electrical properties of reactively sputtered WO 3 thin films as ozone gas sensor  

Microsoft Academic Search

Electrical properties of the metallic oxide semiconductor, such as tungsten trioxide (WO3) thin films, deposited on SiO2\\/Si substrates by RF reactive magnetron sputtering system from a metallic tungsten target and argon–oxygen mixture gas have been investigated. This study is devoted to analyse the relationship between the electrical properties and the WO3 thin film deposition parameters (substrate temperature, oxygen partial pressure,

K Aguir; C Lemire; D. B. B Lollman

2002-01-01

66

Thick film hydrogen sensor  

DOEpatents

A thick film hydrogen sensor element includes an essentially inert, electrically-insulating substrate having deposited thereon a thick film metallization forming at least two resistors. The metallization is a sintered composition of Pd and a sinterable binder such as glass frit. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors.

Hoffheins, Barbara S. (Knoxville, TN); Lauf, Robert J. (Oak Ridge, TN)

1995-01-01

67

Thick film hydrogen sensor  

DOEpatents

A thick film hydrogen sensor element includes an essentially inert, electrically-insulating substrate having deposited thereon a thick film metallization forming at least two resistors. The metallization is a sintered composition of Pd and a sinterable binder such as glass frit. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors. 8 figs.

Hoffheins, B.S.; Lauf, R.J.

1995-09-19

68

Discrimination of individual gas\\/odor using responses of integrated thick film tin oxide sensor array and fuzzy-neuro concept  

Microsoft Academic Search

A new neural network classifier for an Intelligent Gas Sensor (IGS) application is presented. The classifier is trained on fuzzyfied training set. Its superior classification and learning performance is demonstrated for discrimination of alcohols and alcoholic beverages using published data of thick film tin oxide sensor array fabricated and characterized at our laboratory. The new model proposed in this article

R. R. Das; K. K. Shukla; R. Dwivedi; A. R. Srivastava

1999-01-01

69

Fiber optic gas sensor  

NASA Technical Reports Server (NTRS)

A gas sensor includes an in-fiber resonant wavelength device provided in a fiber core at a first location. The fiber propagates a sensing light and a power light. A layer of a material is attached to the fiber at the first location. The material is able to absorb the gas at a temperature dependent gas absorption rate. The power light is used to heat the material and increases the gas absorption rate, thereby increasing sensor performance, especially at low temperatures. Further, a method is described of flash heating the gas sensor to absorb more of the gas, allowing the sensor to cool, thereby locking in the gas content of the sensor material, and taking the difference between the starting and ending resonant wavelengths as an indication of the concentration of the gas in the ambient atmosphere.

Chen, Peng (Inventor); Buric, Michael P. (Inventor); Swinehart, Philip R. (Inventor); Maklad, Mokhtar S. (Inventor)

2010-01-01

70

Characterization of thin MoO3 films formed by RF and DC-magnetron reactive sputtering for gas sensor applications  

NASA Astrophysics Data System (ADS)

The present work discusses a technology for deposition and characterization of thin molybdenum oxide (MoOx, MoO3) films studied for gas sensor applications. The samples were produced by reactive radio-frequency (RF) and direct current (DC) magnetron sputtering. The composition and microstructure of the films were studied by XPS, XRD and Raman spectroscopy, the morphology, using high resolution SEM. The research was focused on the sensing properties of the sputtered thin MoO3 films. Highly sensitive gas sensors were implemented by depositing films of various thicknesses on quartz resonators. Making use of the quartz crystal microbalance (QCM) method, these sensors were capable of detecting changes in the molecular range. Prototype QCM structures with thin MoO3 films were tested for sensitivity to NH3 and NO2. Even in as-deposited state and without heating the substrates, these films showed good sensitivity. Moreover, no additional thermal treatment is necessary, which makes the production of such QCM gas sensors simple and cost-effective, as it is fully compatible with the technology for producing the initial resonator. The films are sensitive at room temperature and can register concentrations as low as 50 ppm. The sorption is fully reversible, the films are stable and capable of long-term measurements.

Yordanov, R.; Boyadjiev, S.; Georgieva, V.; Vergov, L.

2014-05-01

71

Sensitive, selective and stable tin dioxide thin-films for carbon monoxide and hydrogen sensing in integrated gas sensor array applications  

Microsoft Academic Search

This paper reports on the preparation, electrical and surface characterization of Cu doped tin dioxide thin-films for highly selective integrated gas sensor devices. The 3000Å thin-film of 0.16wt.% copper doped tin dioxide was deposited by reactive R.F. sputtering at room temperature and followed by 10Å Pt on top of Cu doped tin dioxide thin-film (SnO2–Cu\\/Pt). In another batch, the 100Å

Rajnish K Sharma; Philip C. H Chan; Zhenan Tang; G Yan; I-Ming Hsing; Johnny K. O Sin

2001-01-01

72

Oxide Semiconductor Gas Sensors  

Microsoft Academic Search

Semiconductor gas sensors utilize porous polycrystalline resistors made of semiconducting oxides. The working principle involves the receptor function played by the surface of each oxide grain and the transducer function played by each grain boundary. In addition, the utility factor of the sensing body also takes part in determining the gas response. Therefore, the concepts of sensor design are determined

Noboru Yamazoe; Go Sakai; Kengo Shimanoe

2003-01-01

73

Photochemical Deposition of Semiconductor Thin Films and Their Application for Solar Cells and Gas Sensors  

SciTech Connect

The photochemical deposition (PCD) technique was applied for solar cells and gas sensors. CdS and Cd{sub 1-x}Zn{sub x}S were deposited by PCD. Thiosulfate ions S{sub 2}O{sub 3}{sup 2-} act as a reductant and a sulfur source. The SnS absorption layer was deposited by three-step pulse electrochemical deposition. For the CdS/SnS structure, the best cell showed an efficiency of about 0.2%, while for the Cd{sub 1-x}Zn{sub x}S/SnS structure, an efficiency of up to 0.7% was obtained. For the gas sensor application, SnO{sub 2} was deposited by PCD from a solution containing SnSO{sub 4} and HNO{sub 3}. To enhance the sensitivity to hydrogen, Pd was doped by the photochemical doping method. The current increased by a factor of 10{sup 4} upon exposure to 5000 ppm hydrogen within 1 min at room temperature. 10{sup 3} times conductivity increase was observed even for 50 ppm hydrogen.

Ichimura, M.; Gunasekaran, M.; Sueyoshi, T. [Dept. Engineering Physics, Electronics and Mechanics, Nagoya Institute of Technology Gokiso, Showa, Nagoya 466-8555 (Japan)

2009-06-01

74

Photochemical Deposition of Semiconductor Thin Films and Their Application for Solar Cells and Gas Sensors  

NASA Astrophysics Data System (ADS)

The photochemical deposition (PCD) technique was applied for solar cells and gas sensors. CdS and Cd1-xZnxS were deposited by PCD. Thiosulfate ions S2O32- act as a reductant and a sulfur source. The SnS absorption layer was deposited by three-step pulse electrochemical deposition. For the CdS/SnS structure, the best cell showed an efficiency of about 0.2%, while for the Cd1-xZnxS/SnS structure, an efficiency of up to 0.7% was obtained. For the gas sensor application, SnO2 was deposited by PCD from a solution containing SnSO4 and HNO3. To enhance the sensitivity to hydrogen, Pd was doped by the photochemical doping method. The current increased by a factor of 104 upon exposure to 5000 ppm hydrogen within 1 min at room temperature. 103 times conductivity increase was observed even for 50 ppm hydrogen.

Ichimura, M.; Gunasekaran, M.; Sueyoshi, T.

2009-06-01

75

Nanoparticle engineering for gas sensor optimisation: improved sol–gel fabricated nanocrystalline SnO 2 thick film gas sensor for NO 2 detection by calcination, catalytic metal introduction and grinding treatments  

Microsoft Academic Search

The control of the technological steps such as calcination temperature and introduction of catalytic additives are accepted to be key points in the obtaining of improved sol–gel fabricated SnO2 thick film gas sensors with different sensitivity to NO2 and CO. In this work, after proving that the undoped material calcined at 1000°C is optimum for NO2 detection, grinding is added

A. Diéguez; A. Romano-Rodr??guez; J. R. Morante; J. Kappler; N. Bârsan; W. Göpel

1999-01-01

76

A fully neural implementation of unitary response model for classification of gases\\/odors using the responses of thick film gas sensor array  

Microsoft Academic Search

In this paper, a classification scheme based on neurally implemented unitary response model (URM) for a gas\\/odor sensor array response has been presented. Thick-film tin-oxide sensor array responses for four gases\\/odors (viz. acetone, carbon tetra-chloride, ethyl methyl ketone and xylene) were first transformed into equivalent unitary responses. This transformation was carried out using a pre-trained neural ‘unitary response model pre-processor

N. S. Rajput; R. R. Das; V. N. Mishra; K. P. Singh; R. Dwivedi

2011-01-01

77

Acetone and ethanol solid-state gas sensors based on TiO 2 nanoparticles thin film deposited by matrix assisted pulsed laser evaporation  

Microsoft Academic Search

Matrix assisted pulsed laser evaporation (MAPLE) is a new promising laser-based technique thought for polymer or biomaterial thin films deposition. In this work, the MAPLE technique has been used for the deposition of titania (TiO2) nanoparticle thin films to be used for gas sensor applications. For this purpose, an aqueous solution of TiO2 nanoparticles, synthesized by a novel chemical route,

R. Rella; J. Spadavecchia; M. G. Manera; S. Capone; A. Taurino; M. Martino; A. P. Caricato; T. Tunno

2007-01-01

78

Response characteristics of a potentiometric CO2 gas sensor based on Li3PO4 solid electrolyte using Au film as the electrodes  

NASA Astrophysics Data System (ADS)

A potentiometric CO2 gas sensor based on Li3PO4 film with the thickness of 0.8 ?m prepared by thermal evaporation method was developed. Au thin film with the thickness of 400 nm deposited by sputtering method was used as the metal electrodes of the sensor. Li2CO3 and Li2TiO3 with 10 mol. % TiO2 were used as the sensing and reference electrodes by screen printing the materials on the Au thin film electrodes, respectively. Response characteristics of the sensor to CO2 in the range of 250 ppm to 5000 ppm at different working temperatures were investigated. The electromotive force (EMF) values of the sensor were linearly dependent on logarithm of CO2 partial pressure at the temperatures between 420 °C and 530 °C. Dependence of response and recovery time, initial EMF, ?EMF/dec on working temperature was presented. It can be found that the response time and recovery time reduced with the enhancement of working temperature and gradually reached to the limit when the temperature is above 500 °C. However, the maximum ?EMF/dec value was obtained at the temperature of 440 °C. The dependence of ?EMF/dec on working temperature was newly found and different from previous research. The results suggest potential use of thin film metal electrodes in solid electrolyte gas sensors for lower temperature and miniature applications.

Sun, Guoliang; Wang, Hairong; Li, Peng; Liu, Zhen; Jiang, Zhuangde

2014-03-01

79

Microfabricated Formaldehyde Gas Sensors  

PubMed Central

Formaldehyde is a volatile organic compound that is widely used in textiles, paper, wood composites, and household materials. Formaldehyde will continuously outgas from manufactured wood products such as furniture, with adverse health effects resulting from prolonged low-level exposure. New, microfabricated sensors for formaldehyde have been developed to meet the need for portable, low-power gas detection. This paper reviews recent work including silicon microhotplates for metal oxide-based detection, enzyme-based electrochemical sensors, and nanowire-based sensors. This paper also investigates the promise of polymer-based sensors for low-temperature, low-power operation.

Flueckiger, Jonas; Ko, Frank K.; Cheung, Karen C.

2009-01-01

80

Development of novel low-temperature selective hydrogen gas sensors made of palladium/oxide or nitride capped Magnesium-transition metal hydride films  

NASA Astrophysics Data System (ADS)

Palladium capped Mg-based transition metal alloy film (Pd/Mg-TM) is a potentially useful hydrogen gas (H2) sensing material, which can operate at low temperature for detection of H2 leakage in an environment to ensure safe use and storage of the gas. The Pd layer catalytically dissociates hydrogen molecules, and the hydrogen atoms produced can enter (hydridation) or be detached (dehydridation) from the alloy layer. These processes are reversible, such that the film is switchable between a metal state and a hydride state, giving rise to substantial changes in its optical transmittance/reflectance and electrical resistivity. Unlike a conventional metal-oxide (MOx) H2 sensor, hydridation of an Mg-TM film is associated with relatively low enthalpy, and hence can perform at temperature much lower than the operation temperature of an MOx sensor (typically around 500°C or above). As such, an Mg-TM based sensor does not experience undesired annealing effect during operation, and hence is much more stable and durable. Furthermore, the detection selectivity of a Pd/Mg-TM film versus other reducing gases is superior to most conventional MOx-type hydrogen sensors. In this project, we systematically investigated the H2 sensing properties of Pd/Mg-TM films.

Tang, Yu Ming

81

Direct thermoelectric gas sensors: Design aspects and first gas sensors  

Microsoft Academic Search

Design aspects for novel direct thermoelectric gas sensors are discussed. Such sensors are based on materials that directly change their material property Seebeck coefficient with the ambient gas atmosphere. Since the measurement principle is a potentiometric one, a very good stability in harsh environments is expected, especially when compared to resistive gas sensors. In contrast to the potentiometric lambda sensor,

Frank Rettig; Ralf Moos

2007-01-01

82

Thin film porous membranes for catalytic sensors  

SciTech Connect

This paper reports on new and surprising experimental data for catalytic film gas sensing resistors coated with nanoporous sol-gel films to impart selectivity and durability to the sensor structure. This work is the result of attempts to build selectivity and reactivity to the surface of a sensor by modifying it with a series of sol-gel layers. The initial sol-gel SiO{sub 2} layer applied to the sensor surprisingly showed enhanced O{sub 2} interaction with H{sub 2} and reduced susceptibility to poisons such as H{sub 2}S.

Hughes, R.C.; Boyle, T.J.; Gardner, T.J. [and others

1997-06-01

83

Calorimetric gas sensor  

DOEpatents

A combustible gas sensor that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2 .mu.m thick.times.10 .mu.m wide.times.100, 250, 500, or 1000 .mu.m-long polycrystalline Si; some are overcoated with a 0.25 .mu.m-thick protective CVD Si.sub.3 N.sub.4 layer. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac).sub.2 onto microfilaments resistively heated to approximately 500.degree. C.; Pt deposits only on the hot filament. Using a constant-resistance-mode feedback circuit, Pt-coated filaments operating at ca. 300.degree. C. (35 mW input power) respond linearly, in terms of the change in supply current required to maintain constant resistance (temperature), to H.sub.2 concentrations between 100 ppm and 1% in an 80/20 N.sub.2 /O.sub.2 mixture. Other catalytic materials can also be used.

Ricco, Antonio J. (Albuquerque, NM); Hughes, Robert C. (Cedar Crest, NM); Smith, James H. (Albuquerque, NM); Moreno, Daniel J. (Albuquerque, NM); Manginell, Ronald P. (Albuquerque, NM); Senturia, Stephen D. (Brookline, MA); Huber, Robert J. (Bountiful, UT)

1998-01-01

84

Calorimetric gas sensor  

DOEpatents

A combustible gas sensor is described that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2 {micro}m thick {times} 10{micro}m wide {times} 100, 250, 500, or 1000 {micro}m-long polycrystalline Si; some are overcoated with a 0.25 {micro}m-thick protective CVD Si{sub 3}N{sub 4} layer. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac){sub 2} onto microfilaments resistively heated to approximately 500 C; Pt deposits only on the hot filament. Using a constant-resistance-mode feedback circuit, Pt-coated filaments operating at ca. 300 C (35 mW input power) respond linearly, in terms of the change in supply current required to maintain constant resistance (temperature), to H{sub 2} concentrations between 100 ppm and 1% in an 80/20 N{sub 2}/O{sub 2} mixture. Other catalytic materials can also be used. 11 figs.

Ricco, A.J.; Hughes, R.C.; Smith, J.H.; Moreno, D.J.; Manginell, R.P.; Senturia, S.D.; Huber, R.J.

1998-11-10

85

Room temperature operated ammonia gas sensor using polycarbazole Langmuir–Blodgett film  

Microsoft Academic Search

Langmuir–Blodgett (LB) and spin casting techniques were utilized for preparing thin films of pure polycarbazole, and polycarbazole mixed with octadecylamine (ODA). These films were characterized by using UV–vis absorbance spectroscopy and cyclic voltammetry (CV). Sensitivity of these ultra-thin films to ammonia was studied by measuring changes in electrical resistance. It was found that pure polycarbazole LB films have higher sensitivity,

Vibha Saxena; Sipra Choudhury; S. C. Gadkari; S. K. Gupta; J. V. Yakhmi

2005-01-01

86

Gas Sensors Based on Electrospun Nanofibers  

PubMed Central

Nanofibers fabricated via electrospinning have specific surface approximately one to two orders of the magnitude larger than flat films, making them excellent candidates for potential applications in sensors. This review is an attempt to give an overview on gas sensors using electrospun nanofibers comprising polyelectrolytes, conducting polymer composites, and semiconductors based on various sensing techniques such as acoustic wave, resistive, photoelectric, and optical techniques. The results of sensing experiments indicate that the nanofiber-based sensors showed much higher sensitivity and quicker responses to target gases, compared with sensors based on flat films.

Ding, Bin; Wang, Moran; Yu, Jianyong; Sun, Gang

2009-01-01

87

Highly sensitive SnO 2 thin film NO 2 gas sensor operating at low temperature  

Microsoft Academic Search

Thin films of pure nano-crystalline SnO2 and WO3-doped SnO2 in different concentrations (3wt.% and 5wt.%) are deposited using sol–gel spin coating technique on glass substrates. The structural and morphological properties of these films are investigated using XRD, TEM and AFM. The sensitivity and selectivity of these films are tested to different reducing and oxidizing gases such as SO2, NH3, NO2

Jaswinder Kaur; Somnath C. Roy; M. C. Bhatnagar

2007-01-01

88

Novel NO 2 gas sensor based on cuprous oxide thin films  

Microsoft Academic Search

In this paper we present the results concerning the characterization of cuprous oxide thin films fabricated by chemical deposition and rapid photothermal processing (RPP) method. The growth kinetic effects and influence of the RPP temperature on the chemical deposited cuprous oxide thin films microstructures were investigated by scanning electron microscopy and energy dispersive X-ray spectrometry. The effect of the electrical

Sergiu T. Shishiyanu; Teodor S. Shishiyanu; Oleg I. Lupan

2006-01-01

89

Study of thin-film SO2 gas sensors by photometric and ellipsometric methods  

NASA Astrophysics Data System (ADS)

Pt-, Pd-, and Zr-doped SnO2 thin films and dopant-free VOx films were fabricated by planar magnetron sputtering. Tests for sensitivity to SO2 for all samples were conducted at 180 degree(s)C, and the sensitivities were investigated ex situ with photometric and ellipsometric methods are room temperature. It was found that the optical sensitivities as well as the sensitive wavelength region for SnO2 films could be tuned by doping. The Pd-doped SnO2 films had good sensitivity in the visible range, and the Zr-doped in the near IR. The dominant sensitive wavelength region for VOx films fell into the visible range, and the ratio of the sensitivity in the visible so that in the near IR increased with O2/Ar in the depositing atmosphere.

Tang, Zhaosheng; Fan, Zhengxiu; Shao, Jianda

2001-05-01

90

Influence of film thickness on the properties of sprayed ZnO thin films for gas sensor applications  

NASA Astrophysics Data System (ADS)

Transparent conducting ZnO films were prepared at substrate temperature 400 °C with different film thicknesses by nebulizer spray pyrolysis method on glass substrates. XRD studies reveal that the films are polycrystalline in nature having hexagonal crystal structure with preferred grain orientations along (0 0 2) and (1 0 1) directions. The crystallite size increases along (0 0 2) plane with the thickness increase and attains a maximum 109 nm for 913 nm film thickness. Analysis of structural parameters indicates that the films having thickness 913 nm are found to have minimum dislocation density and strain values. The HRSEM measurements show that the surface morphology of the films also changes with film thickness. EDAX estimates the average atomic percentage ratio of Zn and O in the ZnO films. Optical studies reveal the band gap energy decrease from 3.27 to 3.14 eV with increase of film thickness. Room temperature PL spectra show the near-band-edge emission and deep-level emission due to the presence of defects in the ZnO thin films. Impedance spectroscopy analysis indicates that grain boundary resistance decreases with the increasing ammonia concentration up to 500 ppm and the maximum sensitivity is found to be 1.7 for 500 ppm of ammonia.

Mariappan, R.; Ponnuswamy, V.; Suresh, P.; Ashok, N.; Jayamurugan, P.; Chandra Bose, A.

2014-07-01

91

SiC-Based Gas Sensor Development  

NASA Technical Reports Server (NTRS)

Silicon carbide based Schottky diode gas sensors are being developed for applications such as emission measurements and leak detection. The effects of the geometry of the tin oxide film in a Pd/SnO2/SiC structure will be discussed as well as improvements in packaging SiC-based sensors. It is concluded that there is considerable versatility in the formation of SiC-based Schottky diode gas sensing structures which will potentially allow the fabrication of a SiC-based gas sensor array for a variety of gases and temperatures.

Hunter, G. W.; Neudeck, P. G.; Gray, M.; Androjna, D.; Chen, L.-Y.; Hoffman, R. W., Jr.; Liu, C. C.; Wu, Q. H.

2000-01-01

92

Nano-grained thin-film indium tin oxide gas sensors for H 2 detection  

Microsoft Academic Search

Nano-grained indium tin oxide (ITO) thin films catalyzed 0.5wt.% Pd were deposited on the alumina substrate at ambient temperature or 300°C by using an rf magnetron sputtering system and then annealed at 650°C for 1 or 4h in air. The crystallinity and microstructure of the annealed films were analyzed. The effects of their microstructure (nano-grain) and ITO composition on H2

Kwang Soo Yoo; Sang Hyoun Park; Ju Hyun Kang

2005-01-01

93

Thick oxidised porous silicon layer as a thermo-insulating membrane for high-temperature operating thin- and thick-film gas sensors  

Microsoft Academic Search

A technological process aiming to realise oxidised porous silicon (OPS) layers as thermo-insulating material, for thin- as well as thick-film gas sensor applications, is reported and discussed. OPS layers (5–35 ?m thick) have been realised on p-Si substrates using the Si anodisation process followed by the PS thermal oxidation. A phosphorus implantation of patterned Si substrates has been performed to

P. Maccagnani; R. Angelucci; P. Pozzi; A. Poggi; L. Dori; G. C. Cardinali; P. Negrini

1998-01-01

94

Quartz crystal microbalance coated with sol–gel-derived indium–tin oxide thin films as gas sensor for NO detection  

Microsoft Academic Search

This paper presents the possibilities and properties of indium–tin oxide (ITO)-covered quartz crystal microbalances (QCM) as a NOx toxic gas sensors. The starting sol–gel solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol (0–20% by weight). The ITO thin films were deposited on the gold electrodes of quartz crystals by spin-coating and annealing

J Zhang; J Hu; Z. Q Zhu; H Gong; S. J O’Shea

2004-01-01

95

Tin oxide and iron doped tin oxide thin films as gas sensors  

Microsoft Academic Search

Monitoring of toxic, inflammable and green house gases have become a major concern for present day industries. Detecting low concentrations of such gases has proven to prevent accidents that could occur due to leakage or ignition of gas. Thus gas sensing has grown into a field of research. ^ There are many green house gases that need to be monitored,

Abhishek Sundararajan

2007-01-01

96

Preparation and gas-sensing properties of Ce-doped ZnO thin-film sensors by dip-coating  

Microsoft Academic Search

CeO2-doped ZnO thin-film gas sensors with different Ce\\/Zn ratios have been fabricated by dip-coating method, starting from zinc acetate dihydrate, cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and anhydrous ethanol. Each layer was fired at 180°C in a conventional oven for 30min and the final coatings were sintered at 500°C in a muffle furnace for 60min. The microstructure and morphology of the films

Chunqiao Ge; Changsheng Xie; Shuizhou Cai

2007-01-01

97

Investigations into the response of an optical gas sensor based on polymeric LB films  

Microsoft Academic Search

The response of an NO2 sensing system based on LB films of a polysiloxane with azobenzene chromophoric side-chains has been investigated. Changes in absorbance on exposure to 100 ppm NO2 have been recorded using UV-visible absorption spectroscopy from which changes in extinction coefficient (?k ? 0.033 at 500 nm) have been determined. Shallow angle X-ray reflectivity (SAXR) studies indicate a

D. A. Parry; M. Mat Sallah; L. S. Miller; I. R. Peterson; R. Hollyoak

1997-01-01

98

Synthesis and characterization of tin oxide for thin film gas sensor applications  

NASA Astrophysics Data System (ADS)

Tin oxide derived from sol-gel yielded nano-size crystals. Tin oxide (cassiterite) crystals were present in the sol-gel dried at 100°C, and crystallization rapidly increased at 700°C and above. At temperatures below 700°C, the grain growth kinetics showed a weaker time dependence (grain growth exponent n of 6--7.4) with an activation energy of 20--25 kJ/mol, and no growth anisotropy was observed. At 1100°C, n was about 4, consistent with pore control by surface diffusion as a dominant growth mechanism. The results at high temperatures (950 and 1100°C) showed faster growth along the direction normal to (101) than the [110] direction. No significant grain growth was observed for 10-day anneals at 300°C after the material had been calcined at 600°C or 800°C. Spin-coating of sol-gel materials provides continuous, porous, polycrystalline thin films with nanometer particle size. Particle and pore size increase with heating temperature and time. The films show (101) texture, and this texture becomes enhanced with increasing heat-treatment temperature. For the same fabrication conditions, films on platinum electrodes exhibited more cracks than those on polycrystalline alumina substrates. Rougher substrates resulted in more cracks. The critical film thickness for cracking on alumina substrate with 970 nm roughness was less than that for alumina with 280 nm roughness. Most of the cracks were located in the valleys between alumina grains. Cracking most likely occurs during drying, but these cracks enlarged and widened during subsequent calcining at 700°C. Doping with Ru suppressed SnO2 nucleation from the gel materials and slowed down the grain growth (n = 8.1--8.9) up to 700°C. Ru doping also reduced the (101) texture of the thin film and the peak intensity relationship returned to the values for SnO2 powder (i.e. I 101/I110 = 0.75) at 800°C. Doping with Pt increased SnO 2 grain size due to heterogeneous nucleation in the initial stage of heating. The grain size difference between Pt-doped and undoped SnO2 is larger for 1 h heat-treatment than for 24 h heat-treatment at 500--800°C. For heat-treatments from 1 h up to 24 h, Pt doping significantly suppressed SnO2 grain growth (n = 7.6--11.9), resulting in preferential grain growth in the direction normal to (101). Two kinds of surfactants were studied to modify the substrate. Thiol (-SH) surfactant attached only to screen-printed platinum ink via S-Pt bonds, while trichlorosilyl (-SiCl3) bonding group surfactant attached to both alumina and platinum ink. The hydrophilic sulfonate-modified surfaces promoted film adherence and resistance to ultrasonic agitation. The hydrophobic methyl-modified Pt surfaces exhibited reduced film adhesion.

Tang, Yin

99

Preparation of nanofibrous polyaniline films and their application as ammonia gas sensor  

Microsoft Academic Search

Silicon substrates were surface modified using an amino-silane ((CH3O)3-Si-(CH2)3NH(CH2)2-NH2) self-assembled monolayer (SAM). The amino groups (NH2) of the amino-silane SAM were employed as artificial seeds for self-organization of polyaniline during chemical polymerization of polyaniline. The polyaniline films were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Scanning electron microscopy showed formation of crystalline

D. S. Sutar; N. Padma; D. K. Aswal; S. K. Deshpande; S. K. Gupta; J. V. Yakhmi

2007-01-01

100

Preparation of mesoporous and/or macroporous SnO2-based powders and their gas-sensing properties as thick film sensors.  

PubMed

Mesoporous and/or macroporous SnO(2)-based powders have been prepared and their gas-sensing properties as thick film sensors towards H(2) and NO(2) have been investigated. The mesopores and macropores of various SnO(2)-based powders were controlled by self-assembly of sodium bis(2-ethylhexyl)sulfosuccinate and polymethyl-methacrylate (PMMA) microspheres (ca. 800 nm in diameter), respectively. The introduction of mesopores and macropores into SnO(2)-based sensors increased their sensor resistance in air significantly. The additions of SiO(2) and Sb(2)O(5) into mesoporous and/or macroporous SnO(2) were found to improve the sensing properties of the sensors. The addition of SiO(2) into mesoporous and/or macroporous SnO(2) was found to increase the sensor resistance in air, whereas doping of Sb(2)O(5) into mesoporous and/or macroporous SnO(2) was found to markedly reduce the sensor resistance in air, and to increase the response to 1,000 ppm H(2) as well as 1 ppm NO(2) in air. Among all the sensors tested, meso-macroporous SnO(2) added with 1 wt% SiO(2) and 5 wt% Sb(2)O(5), which were prepared with the above two templates simultaneously, exhibited the largest H(2) and NO(2) responses. PMID:22319350

Yuan, Luyang; Hyodo, Takeo; Shimizu, Yasuhiro; Egashira, Makoto

2011-01-01

101

Preparation of Mesoporous and/or Macroporous SnO2-Based Powders and Their Gas-Sensing Properties as Thick Film Sensors  

PubMed Central

Mesoporous and/or macroporous SnO2-based powders have been prepared and their gas-sensing properties as thick film sensors towards H2 and NO2 have been investigated. The mesopores and macropores of various SnO2-based powders were controlled by self-assembly of sodium bis(2-ethylhexyl)sulfosuccinate and polymethyl-methacrylate (PMMA) microspheres (ca. 800 nm in diameter), respectively. The introduction of mesopores and macropores into SnO2-based sensors increased their sensor resistance in air significantly. The additions of SiO2 and Sb2O5 into mesoporous and/or macroporous SnO2 were found to improve the sensing properties of the sensors. The addition of SiO2 into mesoporous and/or macroporous SnO2 was found to increase the sensor resistance in air, whereas doping of Sb2O5 into mesoporous and/or macroporous SnO2 was found to markedly reduce the sensor resistance in air, and to increase the response to 1,000 ppm H2 as well as 1 ppm NO2 in air. Among all the sensors tested, meso-macroporous SnO2 added with 1 wt% SiO2 and 5 wt% Sb2O5, which were prepared with the above two templates simultaneously, exhibited the largest H2 and NO2 responses.

Yuan, Luyang; Hyodo, Takeo; Shimizu, Yasuhiro; Egashira, Makoto

2011-01-01

102

Thin film oxygen partial pressure sensor  

NASA Technical Reports Server (NTRS)

The development is described of a laboratory model oxygen partial pressure sensor using a sputtered zinc oxide thin film. The film is operated at about 400 C through the use of a miniature silicon bar. Because of the unique resistance versus temperature relation of the silicon bar, control of the operational temperature is achieved by controlling the resistance. A circuit for accomplishing this is described. The response of sputtered zinc oxide films of various thicknesses to oxygen, nitrogen, argon, carbon dioxide, and water vapor caused a change in the film resistance. Over a large range, film conductance varied approximately as the square root of the oxygen partial pressure. The presence of water vapor in the gas stream caused a shift in the film conductance at a given oxygen partial pressure. A theoretical model is presented to explain the characteristic features of the zinc oxide response to oxygen.

Wortman, J. J.; Harrison, J. W.; Honbarrier, H. L.; Yen, J.

1972-01-01

103

Room-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide thin-film transistors  

NASA Astrophysics Data System (ADS)

An organic sensing layer is capped onto an amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) to form a hybrid sensor. The organic layer, served as a second gate, forms a p-n junction with the a-IGZO film. Oxidizing or reducing vapor molecules act like electron acceptors or electron donors to change the potential of the organic layer and the current of a-IGZO TFT. A sensitive and reversible response to 100 ppb ammonia and 100 ppb acetone is obtained at room temperature. This letter opens a route to develop low-cost large-area bio/chemical sensor arrays based on the emerging a-IGZO TFT technology.

Zan, Hsiao-Wen; Li, Chang-Hung; Yeh, Chun-Cheng; Dai, Ming-Zhi; Meng, Hsin-Fei; Tsai, Chuang-Chuang

2011-06-01

104

ANN Modeling of Micro-Machined Gas Sensor Signals  

Microsoft Academic Search

In this paper, an integrated micro-machined gas sensor array, associated with pattern recognition (PARC) techniques, such as artificial neural networks (ANNs), is designed. The proposed sensor design use a number of different sensitive films such as SnO2, TiO2, ZnO, or organic sensitive films to detect different gases. The application of micro-machined Si-based gas sensors in air quality management and emission

Mohamed Gamal El-din; Walied A. Moussa

2005-01-01

105

Room temperature operating ammonia sensor based on tellurium thin films  

Microsoft Academic Search

Tellurium thin films were studied for its use as ammonia gas sensors operable at room temperature. The films showed a reversible increase in resistance when exposed to ammonia and the response was found to be linear in the range of 0–100ppm. The interaction of ammonia with tellurium film was investigated using Raman, XPS and impedance spectroscopy techniques. The results showed

Shashwati Sen; K. P. Muthe; Niraj Joshi; S. C. Gadkari; S. K. Gupta; Jagannath; M. Roy; S. K. Deshpande; J. V. Yakhmi

2004-01-01

106

SiC-Based Gas Sensor Development.  

National Technical Information Service (NTIS)

Silicon carbide based Schottky diode gas sensors are being developed for applications such as emission measurements and leak detection. The effects of the geometry of the tin oxide film in a Pd/SnO2/SiC structure will be discussed as well as improvements ...

C. C. Liu D. Androjna G. W. Hunter L. Y. Chen M. Gray P. G. Neudeck Q. H. Wu R. W. Hoffman

2000-01-01

107

Chemoresistive gas sensor  

DOEpatents

A chemoresistive gas sensor is provided which has improved sensitivity. A layer of organic semiconductor is disposed between two electrodes which, in turn, are connected to a voltage source. High conductivity material is dispersed within the layer of organic semiconductor in the form of very small particles, or islands. The average interisland spacing is selected so that the predominant mode of current flow is by way of electron funneling. Adsorption of gaseous contaminant onto the layer of organic semiconductor modulates the tunneling current in a quantitative manner.

Hirschfeld, Tomas B. (Livermore, CA)

1987-01-01

108

Chemoresistive gas sensor  

DOEpatents

A chemoresistive gas sensor is provided which has improved sensitivity. A layer of organic semiconductor is disposed between two electrodes which, in turn, are connected to a voltage source. High conductivity material is dispersed within the layer of organic semiconductor in the form of very small particles, or islands. The average interisland spacing is selected so that the predominant mode of current flow is by way of electron funneling. Adsorption of gaseous contaminant onto the layer of organic semiconductor modulates the tunneling current in a quantitative manner. 2 figs.

Hirschfeld, T.B.

1987-06-23

109

Improvement of H2S sensing properties of SnO2-based thick film gas sensors promoted with MoO3 and NiO.  

PubMed

The effects of the SnO2 pore size and metal oxide promoters on the sensing properties of SnO2-based thick film gas sensors were investigated to improve the detection of very low H2S concentrations (<1 ppm). SnO2 sensors and SnO2-based thick-film gas sensors promoted with NiO, ZnO, MoO3, CuO or Fe2O3 were prepared, and their sensing properties were examined in a flow system. The SnO2 materials were prepared by calcining SnO2 at 600, 800, 1,000 and 1,200 °C to give materials identified as SnO2(600), SnO2(800), SnO2(1000), and SnO2(1200), respectively. The Sn(12)Mo5Ni3 sensor, which was prepared by physically mixing 5 wt% MoO3 (Mo5), 3 wt% NiO (Ni3) and SnO2(1200) with a large pore size of 312 nm, exhibited a high sensor response of approximately 75% for the detection of 1 ppm H2S at 350 °C with excellent recovery properties. Unlike the SnO2 sensors, its response was maintained during multiple cycles without deactivation. This was attributed to the promoter effect of MoO3. In particular, the Sn(12)Mo5Ni3 sensor developed in this study showed twice the response of the Sn(6)Mo5Ni3 sensor, which was prepared by SnO2(600) with the smaller pore size than SnO2(1200). The excellent sensor response and recovery properties of Sn(12)Mo5Ni3 are believed to be due to the combined promoter effects of MoO3 and NiO and the diffusion effect of H2S as a result of the large pore size of SnO2. PMID:23519347

Lee, Soo Chool; Kim, Seong Yeol; Hwang, Byung Wook; Jung, Suk Yong; Ragupathy, Dhanusuraman; Son, In Sung; Lee, Duk Dong; Kim, Jae Chang

2013-01-01

110

Improvement of H2S Sensing Properties of SnO2-Based Thick Film Gas Sensors Promoted with MoO3 and NiO  

PubMed Central

The effects of the SnO2 pore size and metal oxide promoters on the sensing properties of SnO2-based thick film gas sensors were investigated to improve the detection of very low H2S concentrations (<1 ppm). SnO2 sensors and SnO2-based thick-film gas sensors promoted with NiO, ZnO, MoO3, CuO or Fe2O3 were prepared, and their sensing properties were examined in a flow system. The SnO2 materials were prepared by calcining SnO2 at 600, 800, 1,000 and 1,200 °C to give materials identified as SnO2(600), SnO2(800), SnO2(1000), and SnO2(1200), respectively. The Sn(12)Mo5Ni3 sensor, which was prepared by physically mixing 5 wt% MoO3 (Mo5), 3 wt% NiO (Ni3) and SnO2(1200) with a large pore size of 312 nm, exhibited a high sensor response of approximately 75% for the detection of 1 ppm H2S at 350 °C with excellent recovery properties. Unlike the SnO2 sensors, its response was maintained during multiple cycles without deactivation. This was attributed to the promoter effect of MoO3. In particular, the Sn(12)Mo5Ni3 sensor developed in this study showed twice the response of the Sn(6)Mo5Ni3 sensor, which was prepared by SnO2(600) with the smaller pore size than SnO2(1200). The excellent sensor response and recovery properties of Sn(12)Mo5Ni3 are believed to be due to the combined promoter effects of MoO3 and NiO and the diffusion effect of H2S as a result of the large pore size of SnO2.

Lee, Soo Chool; Kim, Seong Yeol; Hwang, Byung Wook; Jung, Suk Yong; Ragupathy, Dhanusuraman; Son, In Sung; Lee, Duk Dong; Kim, Jae Chang

2013-01-01

111

Thin Film Sensors for Surface Measurements  

NASA Technical Reports Server (NTRS)

Advanced thin film sensors that can provide accurate surface temperature, strain, and heat flux measurements have been developed at NASA Glenn Research Center. These sensors provide minimally intrusive characterization of advanced propulsion materials and components in hostile, high-temperature environments as well as validation of propulsion system design codes. The sensors are designed for applications on different material systems and engine components for testing in engine simulation facilities. Thin film thermocouples and strain gauges for the measurement of surface temperature and strain have been demonstrated on metals, ceramics and advanced ceramic-based composites of various component configurations. Test environments have included both air-breathing and space propulsion-based engine and burner rig environments at surface temperatures up to 1100 C and under high gas flow and pressure conditions. The technologies developed for these sensors as well as for a thin film heat flux gauge have been integrated into a single multifunctional gauge for the simultaneous real-time measurement of surface temperature, strain, and heat flux. This is the first step toward the development of smart sensors with integrated signal conditioning and high temperature electronics that would have the capability to provide feedback to the operating system in real-time. A description of the fabrication process for the thin film sensors and multifunctional gauge will be provided. In addition, the material systems on which the sensors have been demonstrated, the test facilities and the results of the tests to-date will be described. Finally, the results will be provided of the current effort to demonstrate the capabilities of the multifunctional gauge.

Martin, Lisa C.; Wrbanek, John D.; Fralick, Gustave C.

2001-01-01

112

Toward innovations of gas sensor technology  

Microsoft Academic Search

Although gas sensors have been almost matured in some application fields, there are a variety of newly emerging markets and potential markets which will be substantiated when gas sensors are innovated sufficiently. The importance of materials design in innovating gas sensors are demonstrated by taking semiconductor gas sensors and solid electrolyte gas sensors as examples. In addition, attempts to make

Noboru Yamazoe

2005-01-01

113

Photochemistry-based method for the fabrication of SnO(2) monolayer ordered porous films with size-tunable surface pores for direct application in resistive-type gas sensor.  

PubMed

A new photochemistry-based method was introduced for fabricating SnO2 monolayer ordered porous films with size-tunable surface pores on ceramic tubes used for gas sensors. The growth of the spherical pore walls was controlled by two times irradiation of the ultraviolet light using polystyrene microsphere two-dimensional colloidal crystal as a template. The surface pore size of the final obtained porous films was well tuned by changing the second irradiation time rather than replacing the template microspheres. The monolayer ordered porous films on the tubes were directly used, for the first time, as gas sensors. The sensitivity of the sensor depended on the surface pore size and was carefully analyzed by ethanol gas detection. The sensor also exhibited short response-recovery time and long-term stability at lower than 300 °C in practical applications. Therefore, this study opens up a kind of construction method for gas sensors, provides a new strategy for controlling the surface pore size of the monolayer ordered porous film, and introduces a new type of sensitivity-controllable gas sensor. PMID:24410862

Xu, Shipu; Sun, Fengqiang; Gu, Fenglong; Zuo, Yanbing; Zhang, Lihe; Fan, Caifeng; Yang, Shumin; Li, Weishan

2014-01-22

114

Development of a selective gas sensor utilizing a perm-selective zeolite membrane  

Microsoft Academic Search

Reported here is a novel sensor that utilizes a zeolite film to selectively limit gas exposure of the sensing surface. A unique amperometric sensor design based on a non-porous mixed conducting sensing electrode enables the formation of a continuous zeolite film covering the entire sensor surface. The sensor was tested in a variety of oxygen containing gases. The sensor without

W. L. Rauch; M. Liu

2003-01-01

115

A rapid process for fabricating gas sensors.  

PubMed

Zinc oxide (ZnO) is a low-toxicity and environmentally-friendly material applied on devices, sensors or actuators for "green" usage. A porous ZnO film deposited by a rapid process of aerosol deposition (AD) was employed as the gas-sensitive material in a CO gas sensor to reduce both manufacturing cost and time, and to further extend the AD application for a large-scale production. The relative resistance change (?R/R) of the ZnO gas sensor was used for gas measurement. The fabricated ZnO gas sensors were measured with operating temperatures ranging from 110 °C to 180 °C, and CO concentrations ranging from 100 ppm to 1000 ppm. The sensitivity and the response time presented good performance at increasing operating temperatures and CO concentrations. AD was successfully for applied for making ZnO gas sensors with great potential for achieving high deposition rates at low deposition temperatures, large-scale production and low cost. PMID:25010696

Hsiao, Chun-Ching; Luo, Li-Siang

2014-01-01

116

Multi-Gas Sensor  

NASA Technical Reports Server (NTRS)

A multi-gas sensor is provided which modulates a polarized light beam over a broadband of wavelengths between two alternating orthogonal polarization components. The two orthogonal polarization components of the polarization modulated beam are directed along two distinct optical paths. At least one optical path contains one or more spectral discrimination element, with each spectral discrimination element having spectral absorption features of one or more gases of interest being measured. The two optical paths then intersect, and one orthogonal component of the intersected components is transmitted and the other orthogonal component is reflected. The combined polarization modulated beam is partitioned into one or more smaller spectral regions of interest where one or more gases of interest has an absorption band. The difference in intensity between the two orthogonal polarization components is then determined in each partitioned spectral region of interest as an indication of the spectral emission/absorption of the light beam by the gases of interest in the measurement path. The spectral emission/absorption is indicative of the concentration of the one or more gases of interest in the measurement path. More specifically, one embodiment of the present invention is a gas filter correlation radiometer which comprises a polarizer, a polarization modulator, a polarization beam splitter, a beam combiner, wavelength partitioning element, and detection element. The gases of interest are measured simultaneously and, further, can be measured independently or non-independently. Furthermore, optical or electronic element are provided to balance optical intensities between the two optical paths.

Sachse, Glenn W. (Inventor); Wang, Liang-Guo (Inventor); LeBel, Peter J. (Inventor); Steele, Tommy C. (Inventor); Rana, Mauro (Inventor)

1999-01-01

117

A neural net implementation of SPCA pre-processor for gas\\/odor classification using the responses of thick film gas sensor array  

Microsoft Academic Search

In this paper, an artificial neural net (ANN) implementation of SPCA pre-processing is presented for its use with a neural classifier trained with SPCA transformed data. Here, a SPCA transforming neural stage (Net ISPCA) is placed before a SPCA trained neural classifier stage (Net IISPCA). Accordingly, newer sensor array response of respective gas\\/odor can now be classified, more precisely, using

N. S. Rajput; R. R. Das; V. N. Mishra; K. P. Singh; R. Dwivedi

2010-01-01

118

New Gas Polarographic Hydrogen Sensor  

NASA Technical Reports Server (NTRS)

Polarography is the measurement of the current that flows in solution as a function of an applied voltage. The actual form of the observed polarographic current depends upon the manner in which the voltage is applied and on the characteristics of the working electrode. The new gas polarographic H2 sensor shows a current level increment with concentration of the gaseous H2 similar to those relating to metal ions in liquid electrolytes in well-known polarography. This phenomenon is caused by the fact that the diffusion of the gaseous H2 through a gas diffusion hole built in the sensor is a rate-determining step in the gaseous-hydrogen sensing mechanism. The diffusion hole artificially limits the diffusion of the gaseous H2 toward the electrode located at the sensor cavity. This gas polarographic H2 sensor. is actually an electrochemical-pumping cell since the gaseous H2 is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H2 enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H+ ions or protons; H+ ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H2. Gas polarographic 02 sensors are commercially available; a gas polarographic 02 sensor was used to prove the feasibility of building a new gas polarographic H2 sensor.

Dominguez, Jesus A.; Barile, Ron

2004-01-01

119

Multifunctional humidity-gas sensor fabricated on silicon substrate  

Microsoft Academic Search

This paper describes a multifunctional humidity-gas sensor developed with thin-film technology, which is compatible with IC fabrication processes. The sensor is small and inexpensive, being fabricated on a silicon substrate using photolithography. The sensing material is a semiconducting Fe2O3-based thin film which is deposited by rf sputtering on a porous Al2O3 film. The impedance is measured between the top electrode

Kazuhiro Hara; Hidekazu Kawashima

1995-01-01

120

Binary MEMS gas sensors  

NASA Astrophysics Data System (ADS)

A novel sensing mechanism for electrostatic MEMS that employs static bifurcation-based sensing and binary detection is demonstrated. It is implemented as an ethanol vapour sensor that exploits the static pull-in bifurcation. Sensor detection of 5 ppm of ethanol vapour in dry nitrogen, equivalent to a detectable mass of 165 pg, is experimentally demonstrated. Sensor robustness to external disturbances is also demonstrated. A closed-form expression for the sensitivity of statically detected electrostatic MEMS sensors is derived. It is shown that the sensitivity of static bifurcation-based binary electrostatic MEMS sensors represents an upper bound on the sensitivity of static detection for given sensor dimensions and material properties.

Khater, M. E.; Al-Ghamdi, M.; Park, S.; Stewart, K. M. E.; Abdel-Rahman, E. M.; Penlidis, A.; Nayfeh, A. H.; Abdel-Aziz, A. K. S.; Basha, M.

2014-06-01

121

Sensing Characteristics of Flame-Spray-Made Pt/ZnO Thick Films as H2 Gas Sensor  

PubMed Central

Hydrogen sensing of thick films of nanoparticles of pristine, 0.2, 1.0 and 2.0 atomic percentage of Pt concentration doped ZnO were investigated. ZnO nanoparticles doped with 0.2–2.0 at.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique using zinc naphthenate and platinum(II) acetylacetonate as precursors dissolved in xylene. The particle properties were analyzed by XRD, BET, SEM and TEM. Under the 5/5 (precursor/oxygen) flame condition, ZnO nanoparticles and nanorods were observed. The crystallite sizes of ZnO spheroidal and hexagonal particles were found to be ranging from 5 to 20 nm while ZnO nanorods were seen to be 5–20 nm wide and 20–40 nm long. ZnO nanoparticles paste composed of ethyl cellulose and terpineol as binder and solvent respectively was coated on Al2O3 substrate interdigitated with gold electrodes to form thin films by spin coating technique. The thin film morphology was analyzed by SEM technique. The gas sensing properties toward hydrogen (H2) was found that the 0.2 at.% Pt/ZnO sensing film showed an optimum H2 sensitivity of ?164 at hydrogen concentration in air of 1 volume% at 300 °C and a low hydrogen detection limit of 50 ppm at 300 °C operating temperature.

Tamaekong, Nittaya; Liewhiran, Chaikarn; Wisitsoraat, Anurat; Phanichphant, Sukon

2009-01-01

122

Combination of guided mode and photometric optical metrology methods for precise determination of refractive index dispersion: application to polymer blend and ceramic thin films for gas sensors  

NASA Astrophysics Data System (ADS)

Two optical techniques, m-lines and spectroscopic ellipsometry, are compared for their suitability for obtaining the wavelength and the temperature dispersion of the refractive index of thin-film layers used in gas detector devices. Two types of materials that are often integrated into gas sensors are studied: a polymer organic-inorganic blend deposited by spin coating typically used in near-infrared waveguides and the ceramic semiconductor SrTi1-xFexO3 (strontium titanate) doped with iron at concentrations x=0.075 and 0.1 deposited by electron beam deposition. The refractive index dispersion obtained by m-lines and ellipsometry is compared, and the differences between the measured parameters for the two materials are discussed. The chromatic dispersion will be represented by a three-term Cauchy law. An intuitive method for verifying the measured indices using an integrating sphere and reflexion coefficient modeling techniques are also demonstrated. Thermo-optic coefficients in the order of -1×10-4/K for both materials are reported, and very low chromatic dispersions are also measured, thanks to the high sensitivity of the m-lines technique. The uniaxial anisotropic properties of the polymer-blend films are measured and discussed in the case of the semiconductor films.

Wood, Thomas; Le Rouzo, Judikaël; Flory, François; Coudray, Paul; Mastelaro, Valmor Roberto; Pelissari, Pedro; Zilio, Sergio

2013-09-01

123

Combustion Sensors: Gas Turbine Applications.  

National Technical Information Service (NTIS)

This report documents efforts to survey the current research directions in sensor technology for gas turbine systems. The work is driven by the current and future requirements on system performance and optimization. Accurate real time measurements of velo...

M. Human

2002-01-01

124

A polycrystalline diamond thin-film-based hydrogen sensor  

Microsoft Academic Search

A new microelectronic gas sensor utilizing polycrystalline diamond film in conjunction with a catalytic metal has been developed for hydrogen detection. The sensor is fabricated in a layered Pd\\/i-diamond\\/p-diamond metal-insulator-semiconductor (MIS) Schottky-diode configuration on a tungsten substrate. The performance of the sensor for H2 detection has been examined in the temperature range 27-300°C. The analysis of the steady-state reaction kinetics

W. P. Kang; Y. Gurbuz; J. L. Davidson; D. V. Kerns

1995-01-01

125

Porous silicon ammonia gas sensor  

NASA Astrophysics Data System (ADS)

A planar optical waveguide is manufactured by the functionnalisation of oxidised mesoporous silicon with Bromothymol Blue to achieve a sensitive ammonia sensor suitable for low gas concentrations. The propagated light intensity is measured at the output of the waveguide. The sensitivity at low concentrations and the short time of reaction of the sensor are enhanced by a confinement effect of the gas molecules inside the pores. The dependence of the output signal with gas concentration is demonstrated. When the ammonia flow is stopped, the reversibility of the initial characteristics of the propagated light is naturally obtained with the disappearance of the gas molecules.

Chaillou, A.; Charrier, J.; Lorrain, N.; Sarret, M.; Haji, L.

2006-03-01

126

Sub-Nanoliter Spectroscopic Gas Sensor  

PubMed Central

In this work, a new type of optical fiber based chemical sensor, the sub-nanoliter sample cell (SNSC) based gas sensor, is described and compared to existing sensors designs in the literature. This novel SNSC gas sensor is shown to have the capability of gas detection with a cell volume in the sub-nanoliter range. Experimental results for various configurations of the sensor design are presented which demonstrate the capabilities of the miniature gas sensor.

Alfeeli, Bassam; Pickrell, Gary; Wang, Anbo

2006-01-01

127

Binary Channel SAW Mustard Gas Sensor Based on PdPc0.3PANI0.7 hybrid Sensitive Film  

NASA Astrophysics Data System (ADS)

This paper discussed the working principle of binary channel surface acoustic wave (SAW) lithium niobate piezoelectric chip detecting mustard, established the mathematic model of beat frequency output ?f and the mustard gas density ?. The MEMS craft solved the parameters of the binary channel SAW chip such as its interdigital electrode number was 15~25 couple, width and spacing were both 25µm, degree of overlapping was 2mm, fundamental frequency was 10~35MHz, frequency-domain width was 5~20Hz, and its back pt hot film's. According to TG-DSC thermal analysis, vacuum coating craft was adopted to solve the hybrid sensitive film forming craft parameter of PdPc0.3PANI0.7(phthalocyanine palladium0.3Poiyaniline0.7). The micro-appearance of sensitive film was analyzed through SEM. The sensor's sensitivity and response characteristic were tested and analyzed: appear linear change, its response time is less than 5min while its recovery time is less than 8min.

Shi, Y. B.; Xiang, J. J.; Feng, Q. H.; Hu, Z. P.; Zhang, H. Q.; Guo, J. Y.

2006-10-01

128

Development of Hydrogen Gas Sensors Using Quartz Resonator  

NASA Astrophysics Data System (ADS)

The hydrogen gas sensor using quartz resonators is developed to measure less than 4% hydrogen concentration in air. This sensor consists of two quartz resonators. Both sides of electrodes of the sensor resonator are made by platinum thin film. And the reference resonator has Au electrodes. By using this reference resonator, the influence of the temperature and pressure will be canceled. This sensor can measure hydrogen concentration from reaction heat on the platinum catalyst. From experimental results, the frequency of sensor changed linearly in 0% to 5% hydrogen concentrations mixed with the air. The sensor showed 20ppm frequency translation per 1%, and the time constant is about 20 seconds.

Oigawa, Hiroshi; Yamazaki, Daisuke; Ueda, Toshitsugu

129

Solid State Gas Sensor Research in Germany - a Status Report  

PubMed Central

This status report overviews activities of the German gas sensor research community. It highlights recent progress in the field of potentiometric, amperometric, conductometric, impedimetric, and field effect-based gas sensors. It is shown that besides step-by-step improvements of conventional principles, e.g. by the application of novel materials, novel principles turned out to enable new markets. In the field of mixed potential gas sensors, novel materials allow for selective detection of combustion exhaust components. The same goal can be reached by using zeolites for impedimetric gas sensors. Operando spectroscopy is a powerful tool to learn about the mechanisms in n-type and in p-type conductometric sensors and to design knowledge-based improved sensor devices. Novel deposition methods are applied to gain direct access to the material morphology as well as to obtain dense thick metal oxide films without high temperature steps. Since conductometric and impedimetric sensors have the disadvantage that a current has to pass the gas sensitive film, film morphology, electrode materials, and geometrical issues affect the sensor signal. Therefore, one tries to measure directly the Fermi level position either by measuring the gas-dependent Seebeck coefficient at high temperatures or at room temperature by applying a modified miniaturized Kelvin probe method, where surface adsorption-based work function changes drive the drain-source current of a field effect transistor.

Moos, Ralf; Sahner, Kathy; Fleischer, Maximilian; Guth, Ulrich; Barsan, Nicolae; Weimar, Udo

2009-01-01

130

Thin-film piezoelectric acoustic sensors. Application to the detection of hydrocarbons  

Microsoft Academic Search

A novel, based on thin film high-frequency piezotransducer chemical gas sensor was developed and studied in detail. We call it thin film piezoelectric acoustic sensor (TFPAS). It was found to be sensitive in the ppm level to various hydrocarbon vapours in air. The response of the sensors to the presence of the hydrocarbon vapours tested (propane, pentane, hexane, commercial petrol)

L. M. Dorojkine; V. V. Volkov; V. S. Doroshenko; A. A. Lavrenov; D. A. Mourashov; I. A. Rozanov

1997-01-01

131

Functionalized Single Wall Carbon Nanotubes Based Gas Sensor  

Microsoft Academic Search

In this paper we report on functionalized single wall carbon nanotube (SWNT) based gas sensor. SWNT were functionalized with sodium dodecyl sulfate (SDS) which improved solubility of SWNT in the DI water significantly. Solutions of SWNTs were deposited on the alumina substrate prepatterned with Pt contacts and heater to form sensor. The morphology of the SWNT films were characterized by

M. Z. Atashbar; C. Baratto; G. Faglia; G. Sberveglieri

2006-01-01

132

Process for manufacture of thick film hydrogen sensors  

DOEpatents

A thick film process for producing hydrogen sensors capable of sensing down to a one percent concentration of hydrogen in carrier gasses such as argon, nitrogen, and air. The sensor is also suitable to detect hydrogen gas while immersed in transformer oil. The sensor includes a palladium resistance network thick film printed on a substrate, a portion of which network is coated with a protective hydrogen barrier. The process utilizes a sequence of printing of the requisite materials on a non-conductive substrate with firing temperatures at each step which are less than or equal to the temperature at the previous step.

Perdieu, Louisa H. (Overland Park, KS)

2000-09-09

133

Measurement of gas and liquid velocities in an air–water two-phase flow using cross-correlation of signals from a double sensor hot-film probe  

Microsoft Academic Search

Local gas and liquid velocities are measured by cross-correlating signals from a double sensor hot-film anemometer probe in pure water flow and air–water two-phase flow. The gas phase velocity measured in two-phase flow agrees with velocity data obtained using high-speed video to within ±5%. A turbulent structure, present in the liquid phase, allows a correlation to be taken, which is

Barri Gurau; Peter Vassallo; Kurt Keller

2004-01-01

134

Multifunctional Nanowire/film Composites based Bi-modular Sensors for In-situ and Real-time High Temperature Gas Detection  

SciTech Connect

This final report to the Department of Energy/National Energy Technology Laboratory for DE-FE0000870 covers the period from 2009 to June, 2013 and summarizes the main research accomplishments, which can be divided in sensing materials innovation, bimodular sensor demonstration, and new understanding and discoveries. As a matter of fact, we have successfully completed all the project tasks in June 1, 2013, and presented the final project review presentation on the 9th of July, 2013. Specifically, the major accomplishments achieved in this project include: 1) Successful development of a new class of high temperature stable gas sensor nanomaterials based on composite nano-array strategy in a 3D or 2D fashion using metal oxides and perovskite nanostructures. 2) Successful demonstration of bimodular nanosensors using 2D nanofibrous film and 3D composite nanowire arrays using electrical resistance mode and electrochemical electromotive force mode. 3) Series of new discoveries and understandings based on the new composite nanostructure platform toward enhancing nanosensor performance in terms of stability, selectivity, sensitivity and mass flux sensing. In this report, we highlight some results toward these accomplishments.

Gao, Pu-Xian; Lei, Yu

2013-06-01

135

Integrated Mirco-Machined Hydrogen Gas Sensors  

SciTech Connect

The widespread use of hydrogen as both an industrial process gas and an energy storage medium requires fast, selective detection of hydrogen gas. This report discusses the development of a new type of solid-state hydrogen gas sensor that couples novel metal hydride thin films with a MEMS (Micro-Electro-Mechanical System) structure known as a micro-hotplate. In this project, Micro-hotplate structures were overcoated with engineered multilayers that serve as the active hydrogen-sensing layer. The change in electrical resistance of these layers when exposed to hydrogen gas was the measured sensor output. This project focused on achieving the following objectives: (1) Demonstrating the capabilities of micro-machined H2 sensors; (2) Developing an understanding of their performance; (3) Critically evaluating the utility and viability of this technology for life safety and process monitoring applications. In order to efficiently achieve these objectives, the following four tasks were identified: (1) Sensor Design and Fabrication; (2) Short Term Response Testing; (3) Long Term Behavior Investigation; (4) Systems Development. Key findings in the project include: The demonstration of sub-second response times to hydrogen; measured sensitivity to hydrogen concentrations below 200 ppm; a dramatic improvement in the sensor fabrication process and increased understanding of the processing properties and performance relationships of the devices; the development of improved sensing multilayers; and the discovery of a novel strain based hydrogen detection mechanism. The results of this program suggest that this hydrogen sensor technology has exceptional potential to meet the stringent demands of life safety applications as hydrogen utilization and infrastructure becomes more prevalent.

Frank DiMeoJr. Ing--shin Chen

2005-12-15

136

Soap film gas flowmeter  

SciTech Connect

A soap film gas flowmeter is described comprising: a flow tube having a hollow body with opposite open ends through which a soap film is propelled and a first closed chamber housing a soap solution. It also includes means for supporting the flow tube in a substantially vertical position with the open bottom end of the flow tube disposed in the first chamber above the soap solution; a second closed chamber into which the open top end of the flow tube extends and gas inlet means for introducing gas into the first chamber at a flow rate to be measured using the flowmeters. A gas exit means is included for discharging the gas introduced into the first chamber through the second chamber. Plus there are means for generating a single soap bubble from the soap solution substantially at the bottom end of the flow tube and a relatively large opening in the flowtube for providing an open passageway for inlet gas to pass through the flowtube when the bottom open end of the flowtube is covered by the soap solution.

Lalin, H.S.; Bermudez, J.E.; Fleming, W.T.

1987-09-08

137

Gas Sensor Test Chip  

NASA Technical Reports Server (NTRS)

The use of organic polymers to detect gasses has been known for several years to be an effective means for gas detection via conductivity changes. These chemoresistors offer significant advantages over other gas detectors in that they operate near room temperature and thus can be used in compact, low-power applications.

Buehler, M. G.; Ryan, M. A.

1996-01-01

138

Electron Beam Crosslinked Au-nanoparticle Films for Sensor Array Patterning  

NASA Astrophysics Data System (ADS)

We have fabricated chemiresistors, arranged in a 2x2 array with 4 ?m spacing between the sensors, for use in a micro-gas chromatography (?-GC) system. To discriminate between analytes, each sensor should be coated with a different thiol coated Au-nanoparticle film. Due to their close spacing, it is not possible to pattern the sensors with different films with traditional film coating methods. Electron beam exposure crosslinks the nanoparticles and renders the film insoluble, and it possible to selectively expose a single sensor in an array. After crosslinking, the remaining film can be rinsed away leaving one coated sensor. This process can be repeated for different films until all sensors in the array have a distinct coating. Using this technique we have made the smallest chemiresistor array with four different films to date. The sensors were characterized by four volatile organic compounds and exhibit different response patterns making them suitable for ?-GC applications.

Covington, Elizabeth; Kurdak, Cagliyan; Bohrer, Forest; Chang, Hungwei; Zellers, Edward T.

2010-03-01

139

Reductive-gas sensor using iron oxide nanowires  

Microsoft Academic Search

We have proposed and developed a new gas sensor using the change in the permeability of iron oxide nanowires. ?-Fe2O3 nanowires are synthesized by the simple annealing of Fe bulks or films at 375°C in air. When the surface of ?-Fe2O3 nanowires is changed by a reductive gas into ?-Fe2O3 or Fe3O4, the permeability of the nanowires increases. Our sensor

Yuu Uriya; Keisuke Nagato; Tetsuya Hamaguchi; Masayuki Nakao

2011-01-01

140

Fast temperature programmed sensing for micro-hotplate gas sensors  

Microsoft Academic Search

We describe an operating mode of a gas sensor that greatly enhances the capability of the device to determine the composition of a sensed gas. The device consists of a micromachined hotplate with integrated heater, heat distribution plate, electrical contact pads, and sensing film. The temperature programmed sensing (TPS) technique uses millisecond timescale temperature changes to modify the rates for

R. E. Cavicchi; J. S. Suehle; K. G. Kreider; M. Gaitan; P. Chaparala

1995-01-01

141

Comparison of refractive indices measured by m-lines and ellipsometry: application to polymer blend and ceramic thin films for gas sensors  

NASA Astrophysics Data System (ADS)

Two optical techniques, "m-lines" and spectroscopic ellipsometry, are compared for their suitability for obtaining the wavelength and temperature dispersion of the refractive index of thin film layers used in gas detector devices. Two types of materials often integrated into gas sensors are studied: a polymer organic-inorganic blend deposited by spin-coating typically used in near infra-red waveguides and the ceramic semiconductor SrTi1-xFexO3 (strontium titanate) doped with iron at concentrations x = 0.075 and 0.1 deposited by electron beam deposition. In this paper, we will compare the refractive index dispersion obtained by m-lines and ellipsometry, and comment on the differences between the measured parameters for the two materials. The chromatic dispersion will be represented by a three term Cauchy law. An intuitive method of verifying the measured indices using an integrating sphere and reflexion coefficient modelling techniques will also be demonstrated. Thermo-optic coefficients of the order of -1×10-4/K for both materials are reported, and very low chromatic dispersions are also measured thanks to the high sensitivity of the m-lines technique.

Wood, Thomas; Le Rouzo, Judikaël.; Flory, François; Coudray, Paul; Mastelaro, Valmor R.; Pelissari, Pedro; Zilio, Sérgio

2012-10-01

142

Ethanol, acetone and ammonia gas room temperature operated sensor  

NASA Astrophysics Data System (ADS)

CuO nanocrystalline thick films were fabricated from powder synthesized by a sol-gel auto combustion route at different pH value of the precursor solution. The gas sensing response of thick film samples towards ethanol, acetone and ammonia gases has been tested and response has been found to be higher for ammonia gas. The sensor recovers its original state after ammonia exposure.

Singh, Iqbal; Bedi, R. K.

2013-06-01

143

Thin Hot-Film Sensors On Polyimide Film  

NASA Technical Reports Server (NTRS)

Array of closely spaced hot-film sensors with thickness well below critical reference height with regard to air-flow pattern nonintrusively detect laminar boundary-layer transitions with very high resolution. Method developed at NASA Langley Research Center to fabricate such sensors on polyimide films to detect boundary-layer transitions with resolution as high as 0.050 in. These films formed by combination of vacuum deposition and photolithography.

Hopson, Purnell

1993-01-01

144

Thin film porous membranes based on sol-gel chemistry for catalytic sensors  

Microsoft Academic Search

Nanoporous sol-gel based films are finding a wide variety of uses including gas separations and supports for heterogeneous catalysts. The films can be formed by spin or dip coating, followed by relatively low temperature annealing. The authors used several types of these films as coatings on the Pd alloy thin film sensors they had previously fabricated and studied. The sol-gel

R. C. Hughes; S. V. Patel; M. W. Jenkins; T. J. Boyle; T. J. Gardner; C. J. Brinker

1998-01-01

145

Plasma deposited polymers as gas sensitive films  

NASA Astrophysics Data System (ADS)

The possibility is presented of producing thin plasma polymers with desired properties by using nanofillers. Composite films are synthesized from a mixture of hexamethyldisiloxane (HMDSO) and detonation nanodiamond particles (DNDs). The chemical structure of the composite consists of DNDs distributed in the polymer matrix. The effect of DNDs on the humidity and ammonia sorptive properties of the polymers obtained is studied by measuring the mass changes as a result of gas sorption by using a quartz crystal microbalance (QCM). The results show that, in view of building a sensing element for measuring humidity, ammonia or other gases, it is possible to maximize the sensor sensitivity to a certain gas by using an appropriate concentration of DNDs in HMDSO. Thus, a high degree of sensor sensitivity, together with short response time and minimum hysteresis, can be achieved. Composites of plasma-polymerized HMDSO with DNDs can be used as gas sensitive layers for the development of quartz resonator sensors.

Radeva, E.; Georgieva, V.; Lazarov, J.; Vergov, L.; Donkov, N.

2012-03-01

146

Thickness dependence of sensor response for CO gas sensing by tin oxide films grown using atomic layer deposition  

Microsoft Academic Search

Ultrathin tin oxide films were deposited on flat hotplate templates using atomic layer deposition (ALD) techniques with SnCl4 and H2O2 as the reactants. The resistance of the SnOx ALD films across an electrode gap on the hotplate template was observed to oscillate and decrease versus the number of sequential SnCl4 and H2O2 reactions at 250°C. The resistance also varied with

X. Du; S. M. George

2008-01-01

147

Diode-type Gas Sensors Fabricated with a Titania Film on a Ti Plate and Pd-Pt Electrodes -Effects of Polymer Coating on the Hydrogen-sensing Properties-  

NASA Astrophysics Data System (ADS)

H2 responses of a diode-type gas sensor fabricated with a TiO2 film prepared by anodization of a Ti plate and Pd-Pt electrodes (Pd-Pt/TiO2) and the effects of polymer coating on the Pd-Pt/TiO2 sensor were investigated in this study. The H2 response of the Pd-Pt/TiO2 sensor in dry N2 was larger than that in dry air at 250°C, but the addition of moisture into the atmosphere reduced O2 concentration dependence of H2 response. The responses decreased drastically at lower temperature (50°C), but the responses in N2 were larger than those in air under both dry and wet conditions. The coating of polymer on the Pd-Pt/TiO2 sensor increased the H2 responses in wet air and N2 and reduced O2 concentration dependence of H2 responses.

Hyodo, T.; Nakaoka, M.; Kaneyasu, K.; Kato, H.; Yanagi, H.; Shimizu, Y.

2011-10-01

148

Structure and Sensor Properties of Thin Ordered Solid Films  

PubMed Central

Miniaturized gas sensors and biosensors based on nanostructured sensing elements have attracted considerable interest because these nanostructured materials can be used to significantly improve sensor sensitivity and the response time. We report here on a generic, reversible sensing platform based on hybrid nanofilms. Thin ordered Langmuir-Blodgett (LB) films built of fluorene derivatives were used as effective gas sensors for both oxidative and reductive analytes. A novel immobilization method based on thin LB films as a matrix has been developed for construction of sensing protein layers. Biomolecules can often be incorporated into and immobilized on Langmuir-Blodgett films using adsorption methods or by covalent immobilization of proteins. The sensor sensitisation was achieved by an amphiphilic N-alkyl-bis(thiophene)arylenes admixed into the film. The interlaced derivative was expected to facilitate the electron transfer, thereby enhancing the sensor sensitivity. The results suggest that this may be very promising approach for exploring the interactions between proteins and high throughput detection of phenol derivatives in wastewater.

Soloducho, Jadwiga; Cabaj, Joanna; Swist, Agnieszka

2009-01-01

149

Combustion Sensors: Gas Turbine Applications  

NASA Technical Reports Server (NTRS)

This report documents efforts to survey the current research directions in sensor technology for gas turbine systems. The work is driven by the current and future requirements on system performance and optimization. Accurate real time measurements of velocities, pressure, temperatures, and species concentrations will be required for objectives such as combustion instability attenuation, pollutant reduction, engine health management, exhaust profile control via active control, etc. Changing combustor conditions - engine aging, flow path slagging, or rapid maneuvering - will require adaptive responses; the effectiveness of such will be only as good as the dynamic information available for processing. All of these issues point toward the importance of continued sensor development. For adequate control of the combustion process, sensor data must include information about the above mentioned quantities along with equivalence ratios and radical concentrations, and also include both temporal and spatial velocity resolution. Ultimately these devices must transfer from the laboratory to field installations, and thus must become low weight and cost, reliable and maintainable. A primary conclusion from this study is that the optics-based sensor science will be the primary diagnostic in future gas turbine technologies.

Human, Mel

2002-01-01

150

Development of multi-functional sensors in thick-film and thin-film technology  

NASA Astrophysics Data System (ADS)

The paper describes the results of our studies on material processing, design, fabrication and characterization of two kinds of multi-functional solid state sensor in thick-film and thin-film technology. The first sensing device is based on Cr3+ doped perovskite ferroelectric metal oxide Ba1-xSrxTiO3 (x = 0-1) and is fabricated using thick-film technology. Thick films of porous Ba1-xSrxTiO3 exhibit a change in dielectric constant with respect to temperature variations, while their electrical conductivity is a function of humidity. Hence, temperature and humidity can be simultaneously detected by measuring the film capacitance and the film resistance respectively, without incurring crosstalk. The response times of the thick-film sensor to humidity and temperature are 30 seconds and 60 seconds respectively. The second sensor is based on thermally evaporated n-type semiconducting tungsten trioxide (WO3) thin films with a thickness of about 150 nm. It utilizes water physisorption on grain surfaces of WO3 at ambient temperatures as well as O3 chemisorption at elevated temperatures higher than 200 °C. Humidity and O3 can therefore be detected by operating the sensor at different temperature levels. The response times of the thin-film sensor to humidity and O3 are 10 seconds and 30 seconds respectively. In addition, the thin-film Pt heater at the backside of the sensor substrate serves also as a thermometer measuring the temperature of the sensor substrate. Cross-sensitivities among the three measurands, temperature, humidity and gas, are negligible.

Qu, Wenmin; Green, Ray; Austin, Mike

2000-08-01

151

Optical And Structural Properties Of Hydrogenated ZnO Thin Films And Their Application For NH3 Gas Sensors  

NASA Astrophysics Data System (ADS)

Measurements of the optical and structural properties of ZnO thin films (ZnO:H) deposited by magnetron sputtering in an Ar+H2 atmosphere have been performed. The optical band gap, Eopt, and the Urbach band tail width were calculated. The influence of the substrate temperature on the resistivity, optical band gap and structural properties has been studied. A discussion of the influence of Ts on the properties is presented. The sensitivity of ZnO films to exposure to NH3 has been measured by the quartz crystal microbalance method.

Dimova-Malinovska, D.; Lazarova, V.; Angelov, O.; Nichev, H.

2007-04-01

152

Room-temperature gas sensors based on gallium nitride nanoparticles  

NASA Astrophysics Data System (ADS)

Room-temperature sensing characteristics for H 2, ethanol, NH 3, H 2S and water have been investigated with thick-film sensors based on GaN nanoparticles, prepared by a simple chemical route. In general, GaN nanoparticles exhibit satisfactory sensor properties for these gases and vapors even at room temperature. The sensitivity for ethanol is found to be highest, the sensitivity and recovery times being smallest. Gas sensor properties of GaN seem to be related to intrinsic defects, which act as sorption sites for the gas molecules.

Chitara, Basant; Late, Dattatray J.; Krupanidhi, S. B.; Rao, C. N. R.

2010-11-01

153

Qualitative and quantitative analysis of volatile organic compounds using transient and steady-state responses of a thick-film tin oxide gas sensor array  

Microsoft Academic Search

Quantitative analysis of gases, by means of semiconductor sensor arrays and pattern-recognition techniques such as artificial neural networks, has been the goal of a great deal of work over the last few years. However, the lack of selectivity, repeatability and drifts of the sensors, have limited the applications of these systems to qualitative or semi-quantitative gas analysis. While the steady-state

Eduard Llobet; Jesús Brezmes; Xavier Vilanova; Jesús E. Sueiras; Xavier Correig

1997-01-01

154

Micro-sensor thin-film anemometer  

NASA Technical Reports Server (NTRS)

A device for measuring turbulence in high-speed flows is provided which includes a micro-sensor thin-film probe. The probe is formed from a single crystal of aluminum oxide having a 14.degree. half-wedge shaped portion. The tip of the half-wedge is rounded and has a thin-film sensor attached along the stagnation line. The bottom surface of the half-wedge is tilted upward to relieve shock induced disturbances created by the curved tip of the half-wedge. The sensor is applied using a microphotolithography technique.

Sheplak, Mark (Inventor); McGinley, Catherine B. (Inventor); Spina, Eric F. (Inventor); Stephens, Ralph M. (Inventor); Hopson, Jr., Purnell (Inventor); Cruz, Vincent B. (Inventor)

1996-01-01

155

Micromachined polymer-based chemical gas sensor array  

Microsoft Academic Search

We have developed a miniature polymer-based chemical gas sensor array on silicon using micromachining technology. The sensors are polymer–carbon black composite films, which swell reversibly and cause a resistance change upon exposure to a wide variety of gases. We have fabricated two types of devices which can measure this resistance change using a “well” design. These “wells” contain the polymer–carbon

Frank Zee; Jack W. Judy

2001-01-01

156

All thin film magnetoelectric magnetic field sensors  

Microsoft Academic Search

We have fabricated prototype ac magnetic field sensors operating at room temperature based on all thin film ME devices showing strong magnetoelectric (ME) coupling. The ME layers consist of a sol-gel derived Pb(Zr0.52Ti0.48)TiO3 (PZT) film and a dc magnetron sputter deposited magnetostrictive Fe70Ga30 (FeGa) film. The bilayer structures are prepared on micromachined Si wafers, and the laser cutting technique is

Peng Zhao

2009-01-01

157

Electrostatic thin film chemical and biological sensor  

DOEpatents

A chemical and biological agent sensor includes an electrostatic thin film supported by a substrate. The film includes an electrostatic charged surface to attract predetermined biological and chemical agents of interest. A charge collector associated with said electrostatic thin film collects charge associated with surface defects in the electrostatic film induced by the predetermined biological and chemical agents of interest. A preferred sensing system includes a charge based deep level transient spectroscopy system to read out charges from the film and match responses to data sets regarding the agents of interest. A method for sensing biological and chemical agents includes providing a thin sensing film having a predetermined electrostatic charge. The film is exposed to an environment suspected of containing the biological and chemical agents. Quantum surface effects on the film are measured. Biological and/or chemical agents can be detected, identified and quantified based on the measured quantum surface effects.

Prelas, Mark A. (Columbia, MO); Ghosh, Tushar K. (Columbia, MO); Tompson, Jr., Robert V. (Columbia, MO); Viswanath, Dabir (Columbia, MO); Loyalka, Sudarshan K. (Columbia, MO)

2010-01-19

158

Thin-film fiber optic hydrogen and temperature sensor system  

DOEpatents

The invention discloses a sensor probe device for monitoring of hydrogen gas concentrations and temperatures by the same sensor probe. The sensor probe is constructed using thin-film deposition methods for the placement of a multitude of layers of materials sensitive to hydrogen concentrations and temperature on the end of a light transparent lens located within the sensor probe. The end of the lens within the sensor probe contains a lens containing a layer of hydrogen permeable material which excludes other reactive gases, a layer of reflective metal material that forms a metal hydride upon absorbing hydrogen, and a layer of semi-conducting solid that is transparent above a temperature dependent minimum wavelength for temperature detection. The three layers of materials are located at the distal end of the lens located within the sensor probe. The lens focuses light generated by broad-band light generator and connected by fiber-optics to the sensor probe, onto a reflective metal material layer, which passes through the semi-conducting solid layer, onto two optical fibers located at the base of the sensor probe. The reflected light is transmitted over fiber optic cables to a spectrometer and system controller. The absence of electrical signals and electrical wires in the sensor probe provides for an elimination of the potential for spark sources when monitoring in hydrogen rich environments, and provides a sensor free from electrical interferences. 3 figs.

Nave, S.E.

1998-07-21

159

Thin-film fiber optic hydrogen and temperature sensor system  

DOEpatents

The invention discloses a sensor probe device for monitoring of hydrogen gas concentrations and temperatures by the same sensor probe. The sensor probe is constructed using thin-film deposition methods for the placement of a multitude of layers of materials sensitive to hydrogen concentrations and temperature on the end of a light transparent lens located within the sensor probe. The end of the lens within the sensor probe contains a lens containing a layer of hydrogen permeable material which excludes other reactive gases, a layer of reflective metal material that forms a metal hydride upon absorbing hydrogen, and a layer of semi-conducting solid that is transparent above a temperature dependent minimum wavelength for temperature detection. The three layers of materials are located at the distal end of the lens located within the sensor probe. The lens focuses light generated by broad-band light generator and connected by fiber-optics to the sensor probe, onto a reflective metal material layer, which passes through the semi-conducting solid layer, onto two optical fibers located at the base of the sensor probe. The reflected light is transmitted over fiberoptic cables to a spectrometer and system controller. The absence of electrical signals and electrical wires in the sensor probe provides for an elimination of the potential for spark sources when monitoring in hydrogen rich environments, and provides a sensor free from electrical interferences.

Nave, Stanley E. (Evans, GA)

1998-01-01

160

Gas Sensors Based on Conducting Polymers  

PubMed Central

The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.

Bai, Hua; Shi, Gaoquan

2007-01-01

161

A Pt\\/oriented-C hydrogen gas sensor  

Microsoft Academic Search

A Pt\\/C heterojunction has been fabricated and tested as a conductometric hydrogen gas sensor. The carbon layer, deposited between planar Au substrate contacts using a filtered cathodic vacuum arc (with an applied substrate bias of -500 V), consisted largely of vertically oriented graphitic sheets. These sheets have good through-film electrical conductivity and contributed to a low device resistance of ~60

A. Moafi; J. G. Partridge; D. G. McCulloch; A. Z. Sadek; K. Kalantar-zadeh; W. Wlodarski

2009-01-01

162

Detection mechanism of metal oxide gas sensor under UV radiation  

Microsoft Academic Search

The effect of ultraviolet radiation on the sensing mechanism of polycrystalline metal oxide gas sensor has been studied analytically. The model used to describe the sensing mechanism is based on the combination of the neck mechanism and grain boundary mechanism. We found that increasing the UV radiation flux density increases the conductivity of the film by decreasing the resistance. It

Sunita Mishra; C. Ghanshyam; N. Ram; R. P. Bajpai; R. K. Bedi

2004-01-01

163

Zeolite-based Impedimetric Gas Sensor Device in Low-cost Technology for Hydrocarbon Gas Detection  

PubMed Central

Due to increasing environmental concerns the need for inexpensive selective gas sensors is increasing. This work deals with transferring a novel zeolite-based impedimetric hydrocarbon gas sensor principle, which has been originally manufactured in a costly combination of photolithography, thin-film processes, and thick-film processes to a low-cost technology comprising only thick-film processes and one electroplating step. The sensing effect is based on a thin chromium oxide layer between the interdigital electrodes and a Pt-loaded ZSM-5 zeolite film. When hydrocarbons are present in the sensor ambient, the electrical sensor impedance increases strongly and selectively. In the present work, the chromium oxide film is electroplated on Au screen-printed interdigital electrodes and then oxidized to Cr2O3. The electrode area is covered with the screen-printed zeolite. The sensor device is self-heated utilizing a planar platinum heater on the backside. The best sensor performance is obtained at a frequency of 3 Hz at around 350 °C. The good selectivity of the original sensor setup could be confirmed, but a strong cross-sensitivity to ammonia occurs, which might prohibit its original intention for use in automotive exhausts.

Reiss, Sebastian; Hagen, Gunter; Moos, Ralf

2008-01-01

164

Recognizing indoor formaldehyde in binary gas mixtures with a micro gas sensor array and a neural network  

Microsoft Academic Search

Low-concentration formaldehyde (HCHO) together with ethanol\\/toluene\\/acetone\\/alpha-pinene (as an interference gas of HCHO) is detected with a micro gas sensor array, composed of eight tin oxide (SnO2) thin film gas sensors with Au, Cu, Pt or Pd metal catalysts. The characteristics of the multi-dimensional signals from the eight sensors are evaluated. A multilayer neural network with an error backpropagation (BP) learning

Pin Lv; Zhenan Tang; Guangfen Wei; Jun Yu; Zhengxing Huang

2007-01-01

165

Fabrication of Thin Film Heat Flux Sensors  

NASA Technical Reports Server (NTRS)

Prototype thin film heat flux sensors have been constructed and tested. The sensors can be applied to propulsion system materials and components. The sensors can provide steady state and fast transient heat flux information. Fabrication of the sensor does not require any matching of the mounting surface. Heat flux is proportional to the temperature difference across the upper and lower surfaces of an insulation material. The sensor consists of an array of thermocouples on the upper and lower surfaces of a thin insulating layer. The thermocouples for the sensor are connected in a thermopile arrangement. A 100 thermocouple pair heat flux sensor has been fabricated on silicon wafers. The sensor produced an output voltage of 200-400 microvolts when exposed to a hot air heat gun. A 20 element thermocouple pair heat flux sensor has been fabricated on aluminum oxide sheet. Thermocouples are Pt-Pt/Rh with silicon dioxide as the insulating material. This sensor produced an output of 28 microvolts when exposed to the radiation of a furnace operating at 1000 C. Work is also underway to put this type of heat flux sensor on metal surfaces.

Will, Herbert A.

1992-01-01

166

Classification and evaluation of sensing films for QCM odor sensors by steady-state sensor response measurement  

Microsoft Academic Search

When we discriminate gases using quartz crystal microbalances (QCMs) odor sensors, it is important to understand gas sorption characteristics of sensing film materials coated on their electrodes and to select them according to target gases. Although we have so far studied the properties of various kinds of sensing film materials by a flow-type odor sensing system to measure transient responses,

K Nakamura; T Nakamoto; T Moriizumi

2000-01-01

167

Fabrication of an ammonia gas sensor using inkjet-printed polyaniline nanoparticles  

Microsoft Academic Search

This work details the fabrication and performance of a sensor for ammonia gas analysis which has been constructed via the inkjet-printed deposition of polyaniline nanoparticle films. The conducting films were assembled on interdigitated electrode arrays and characterised with respect to their layer thickness and thermal properties. The sensor was further combined with heater foils for operation at a range of

Karl Crowley; Aoife Morrin; Aaron Hernandez; Eimer O’Malley; Philip G. Whitten; Gordon G. Wallace; Malcolm R. Smyth; Anthony J. Killard

2008-01-01

168

Characteristics of hydrogen gas sensor based on a wavelength division multiplexing fiber coupler  

NASA Astrophysics Data System (ADS)

A fiber optic sensor based on the wavelength division multiplexer coated with a palladium (Pd) thin film is designed for hydrogen gas detection. The sensing mechanism of this sensor is measuring the wavelength shift that is induced by the evanescent field interaction with the refractive index change of Pd film when it absorbs hydrogen.

Park, Kwan Seob; Eom, Joo Beom; Park, Min-Su; Kim, Young Ho; Park, Seong Jun; Jang, Jae-Hyeong; Lee, Byeong Ha

2011-05-01

169

Characteristics of hydrogen gas sensor based on a wavelength division multiplexing fiber coupler  

Microsoft Academic Search

A fiber optic sensor based on the wavelength division multiplexer coated with a palladium (Pd) thin film is designed for hydrogen gas detection. The sensing mechanism of this sensor is measuring the wavelength shift that is induced by the evanescent field interaction with the refractive index change of Pd film when it absorbs hydrogen.

Kwan Seob Park; Joo Beom Eom; Min-Su Park; Young Ho Kim; Seong Jun Park; Jae-Hyeong Jang; Byeong Ha Lee

2011-01-01

170

CO Responses of Sensors Based on Cerium Oxide Thick Films Prepared from Clustered Spherical Nanoparticles  

PubMed Central

Various types of CO sensors based on cerium oxide (ceria) have been reported recently. It has also been reported that the response speed of CO sensors fabricated from porous ceria thick films comprising nanoparticles is extremely high. However, the response value of such sensors is not suitably high. In this study, we investigated methods of improving the response values of CO sensors based on ceria and prepared gas sensors from core-shell ceria polymer hybrid nanoparticles. These hybrid nanoparticles have been reported to have a unique structure: The core consists of a cluster of ceria crystallites several nanometers in size. We compared the characteristics of the sensors based on thick films prepared from core-shell nanoparticles with those of sensors based on thick films prepared from conventionally used precipitated nanoparticles. The sensors prepared from the core-shell nanoparticles exhibited a resistance that was ten times greater than that of the sensors prepared from the precipitated nanoparticles. The response values of the gas sensors based on the core-shell nanoparticles also was higher than that of the sensors based on the precipitated nanoparticles. Finally, improvements in sensor response were also noticed after the addition of Au nanoparticles to the thick films used to fabricate the two types of sensors.

Izu, Noriya; Matsubara, Ichiro; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

2013-01-01

171

Room-temperature-functioning ammonia sensor based on solid-state Cu x S films  

Microsoft Academic Search

Resistive gas sensors based on copper sulphide (CuxS) are produced when a thick-film of the CuxS is chemically deposited on the polyethylene (PE) film substrates. The resistance response to gases is investigated for the sensors at the temperatures from 291 to 313 K in air. A correlation of the response to gas with the technology is analysed. It is demonstrated

A Galdikas; A Mironas; V Janickis

2000-01-01

172

Analysis of the sensing mechanism of tin dioxide thin film gas sensors using the change of work function in flammable gas atmosphere  

Microsoft Academic Search

To investigate the sensing mechanism of SnO2 thin films prepared with the targets-facing type sputtering method, the change of work function of the films was measured with the Kelvin method, and was compared with the change of resistance when they were exposed to hydrogen. The change of work function in the same concentration of hydrogen shows different trends according to

Byeongdeok Yea; Ryosuke Konishi; Tomoyuki Osaki; Satoru Abe; Hiroasa Tanioka; Kazunori Sugahara

1996-01-01

173

Platform for a Hydrocarbon Exhaust Gas Sensor Utilizing a Pumping Cell and a Conductometric Sensor  

PubMed Central

Very often, high-temperature operated gas sensors are cross-sensitive to oxygen and/or they cannot be operated in oxygen-deficient (rich) atmospheres. For instance, some metal oxides like Ga2O3 or doped SrTiO3 are excellent materials for conductometric hydrocarbon detection in the rough atmosphere of automotive exhausts, but have to be operated preferably at a constant oxygen concentration. We propose a modular sensor platform that combines a conductometric two-sensor-setup with an electrochemical pumping cell made of YSZ to establish a constant oxygen concentration in the ambient of the conductometric sensor film. In this paper, the platform is introduced, the two-sensor-setup is integrated into this new design, and sensing performance is characterized. Such a platform can be used for other sensor principles as well.

Biskupski, Diana; Geupel, Andrea; Wiesner, Kerstin; Fleischer, Maximilian; Moos, Ralf

2009-01-01

174

Palladium Doped Tin Oxide Based Hydrogen Gas Sensors for Safety Applications  

Microsoft Academic Search

Hydrogen is considered to be a hazardous gas since it forms a flammable mixture between 4 to 75% by volume in air. Hence, the safety aspects of handling hydrogen are quite important. For this, ideally, highly selective, fast response, small size, hydrogen sensors are needed. Although sensors based on different technologies may be used, thin-film sensors based on palladium (Pd)

S. Kasthurirengan; Upendra Behera; D. S. Nadig

2010-01-01

175

Advances in Thin Film Sensor Technologies for Engine Applications  

NASA Technical Reports Server (NTRS)

Advanced thin film sensor techniques that can provide accurate surface strain and temperature measurements are being developed at NASA Lewis Research Center. These sensors are needed to provide minimally intrusive characterization of advanced materials (such as ceramics and composites) and structures (such as components for Space Shuttle Main Engine, High Speed Civil Transport, Advanced Subsonic Transports and General Aviation Aircraft) in hostile, high-temperature environments and for validation of design codes. This paper presents two advanced thin film sensor technologies: strain gauges and thermocouples. These sensors are sputter deposited directly onto the test articles and are only a few micrometers thick; the surface of the test article is not structurally altered and there is minimal disturbance of the gas flow over the surface. The strain gauges are palladium-13% chromium based and the thermocouples are platinum-13% rhodium vs. platinum. The fabrication techniques of these thin film sensors in a class 1000 cleanroom at the NASA Lewis Research Center are described. Their demonstration on a variety of engine materials, including superalloys, ceramics and advanced ceramic matrix composites, in several hostile, high-temperature test environments are discussed.

Lei, Jih-Fen; Martin, Lisa C.; Will, Herbert A.

1997-01-01

176

Pd\\/PVDF thin film hydrogen sensor system based on photopyroelectric purely-thermal-wave interference  

Microsoft Academic Search

A novel sensitive solid-state sensor system for trace hydrogen gas detection has been developed as a next generation device to earlier photopyroelectric (PPE) hydrogen sensors. The basic principle of the sensor is based on the technique of PPE purely-thermal-wave interferometry recently developed in this Laboratory. The active element of the sensor is a thin polyvinylidene fluoride (PVDF) pyroelectric film, sputter-coated

Chinhua Wang; Andreas Mandelis; Jose A. Garcia

1999-01-01

177

Silicon Carbide Gas Sensors for Propulsion Emissions and Safety Applications  

NASA Technical Reports Server (NTRS)

Silicon carbide (SiC) based gas sensors have the ability to meet the needs of a range of aerospace propulsion applications including emissions monitoring, leak detection, and hydrazine monitoring. These applications often require sensitive gas detection in a range of environments. An effective sensing approach to meet the needs of these applications is a Schottky diode based on a SiC semiconductor. The primary advantage of using SiC as a semiconductor is its inherent stability and capability to operate at a wide range of temperatures. The complete SiC Schottky diode gas sensing structure includes both the SiC semiconductor and gas sensitive thin film metal layers; reliable operation of the SiC-based gas sensing structure requires good control of the interface between these gas sensitive layers and the SiC. This paper reports on the development of SiC gas sensors. The focus is on two efforts to better control the SiC gas sensitive Schottky diode interface. First, the use of palladium oxide (PdOx) as a barrier layer between the metal and SiC is discussed. Second, the use of atomically flat SiC to provide an improved SiC semiconductor surface for gas sensor element deposition is explored. The use of SiC gas sensors in a multi-parameter detection system is briefly discussed. It is concluded that SiC gas sensors have potential in a range of propulsion system applications, but tailoring of the sensor for each application is necessary.

Hunter, G. W.; Xu, J.; Neudeck, P. G.; Lukco, D.; Trunek, A.; Spry, D.; Lampard, P.; Androjna, D.; Makel, D.; Ward, B.

2007-01-01

178

Toxic gas response of (In,Sn)O2\\/Pt nanowire sensors  

Microsoft Academic Search

Thin film gas sensors based on tin oxide are fabricated and its characteristics are examined. Target gases are dimethyl methylphosphonate(C3H9O3P, DMMP) as a simulant gas for nerve gas GA (Tabun) and acetonitrile (CH3CN) as a simulant gas for blood gas. Sensing materials are Pt\\/SnO2, where Pt layer (30 Å) is deposited on tin oxide film grown on alumina substrate, (Sn,In)O2\\/Pt

Gi-Hong Rue; Tae-Hyun Ban; Nak-Jin Choi; Jun-Hyuk Kwak; Yeon-Tae Lim; Duk-Dong Lee; Jeung-Soo Huh

2005-01-01

179

A Large Scale Virtual Gas Sensor Array  

NASA Astrophysics Data System (ADS)

This paper depicts a virtual sensor array that allows the user to generate gas sensor synthetic data while controlling a wide variety of the characteristics of the sensor array response: arbitrary number of sensors, support for multi-component gas mixtures and full control of the noise in the system such as sensor drift or sensor aging. The artificial sensor array response is inspired on the response of 17 polymeric sensors for three analytes during 7 month. The main trends in the synthetic gas sensor array, such as sensitivity, diversity, drift and sensor noise, are user controlled. Sensor sensitivity is modeled by an optionally linear or nonlinear method (spline based). The toolbox on data generation is implemented in open source R language for statistical computing and can be freely accessed as an educational resource or benchmarking reference. The software package permits the design of scenarios with a very large number of sensors (over 10000 sensels), which are employed in the test and benchmarking of neuromorphic models in the Bio-ICT European project NEUROCHEM.

Ziyatdinov, Andrey; Fernández-Diaz, Eduard; Chaudry, A.; Marco, Santiago; Persaud, Krishna; Perera, Alexandre

2011-09-01

180

All thin film magnetoelectric magnetic field sensors.  

NASA Astrophysics Data System (ADS)

We have fabricated prototype ac magnetic field sensors operating at room temperature based on all thin film ME devices showing strong magnetoelectric (ME) coupling. The ME layers consist of a sol-gel derived Pb(Zr0.52Ti0.48)TiO3 (PZT) film and a dc magnetron sputter deposited magnetostrictive Fe70Ga30 (FeGa) film. The bilayer structures are prepared on micromachined Si wafers, and the laser cutting technique is used to release and isolate the cantilevers for optimization of the sensor performance. The PZT layer and the FeGa layer couple via the piezoelectric d31 mode and the corresponding ME coupling coefficient is as high as 2 V/(Oe cm) for a lateral dimension of 1 mm^2 device at the mechanical resonant frequency of 333 Hz of a Si cantilever. The soft magnetic FeGa film requires dc bias magnetic field of around 90 Oe to operate the thin film ME device. The coupling between the PZT and the FeGa films is remarkably improved by depositing a 40 nm thick Pt intermediate layer. The clamping effect on the ME coupling is dramatically reduced by back-etching the Si cantilever down to 35 ?m thick. The present work indicates presence of robust ME coupling in microfabricated multilayer thin film ME devices.

Zhao, Peng

2009-03-01

181

Vehicle exhaust gas chemical sensors using acoustic wave resonators  

SciTech Connect

Under Sandia`s Laboratory Directed Research and Development (LDRD) program, novel acoustic wave-based sensors were explored for detecting gaseous chemical species in vehicle exhaust streams. The need exists for on-line, real-time monitors to continuously analyze the toxic exhaust gases -- nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC) -- for determining catalytic converter efficiency, documenting compliance to emission regulations, and optimizing engine performance through feedback control. In this project, the authors adapted existing acoustic wave chemical sensor technology to the high temperature environment and investigated new robust sensor materials for improving gas detection sensitivity and selectivity. This report describes one new sensor that has potential use as an exhaust stream residual hydrocarbon monitor. The sensor consists of a thickness shear mode (TSM) quartz resonator coated with a thin mesoporous silica layer ion-exchanged with palladium ions. When operated at temperatures above 300 C, the high surface area film catalyzes the combustion of the hydrocarbon vapors in the presence of oxygen. The sensor acts as a calorimeter as the exothermic reaction slightly increases the temperature, stressing the sensor surface, and producing a measurable deviation in the resonator frequency. Sensitivities as high as 0.44 (ppm-{Delta}f) and (ppm-gas) have been measured for propylene gas, with minimum detectable signals of < 50 ppm of propylene at 500 C.

Cernosek, R.W.; Small, J.H.; Sawyer, P.S.; Bigbie, J.R. [Sandia National Labs., Albuquerque, NM (United States); Anderson, M.T. [3M Industrial and Consumer Sector Research Lab., St. Paul, MN (United States)

1998-03-01

182

SiC-Based Gas Sensors  

NASA Technical Reports Server (NTRS)

Electronic grade Silicon Carbide (SiC) is a ceramic material which can operate as a semiconductor at temperatures above 600 C. Recently, SiC semiconductors have been used in Schottky diode gas sensor structures. These sensors have been shown to be functional at temperatures significantly above the normal operating range of Si-based devices. SiC sensor operation at these higher temperatures allows detection of gases such as hydrocarbons which are not detectable at lower temperatures. This paper discusses the development of SiC-based Schottky diode gas sensors for the detection of hydrogen, hydrocarbons, and nitrogen oxides (NO(x)). Sensor designs for these applications are discussed. High sensitivity is observed for the hydrogen and hydrocarbon sensors using Pd on SiC Schottky diodes while the NO(x) sensors are still under development. A prototype sensor package has been fabricated which allows high temperature operation in a room temperature ambient by minimizing heat loss to that ambient. It is concluded that SiC-based gas sensors have considerable potential in a variety of gas sensing applications.

Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Knight, Dak; Liu, C. C.; Wu, Q. H.

1997-01-01

183

Zeolitic imidazolate framework as formaldehyde gas sensor.  

PubMed

Traditional semiconducting metal oxide-based gas sensors are always limited on low surface areas and high operating temperatures. Considering the high surface area and high stability of zeolitic imidazolate framework (ZIF), ZIF-67 (surface area of 1832.2 m(2) g(-1)) was first employed as a promising formaldehyde gas sensor at a low operating temperature (150 °C), and the gas sensor could detect formaldehyde as low as 5 ppm. This work develops a new promising application approach for porous metal-organic frameworks. PMID:24813234

Chen, Er-Xia; Yang, Hui; Zhang, Jian

2014-06-01

184

High Sensitive Formaldehyde Gas Sensor Prepared by R.F. Induction Plasma Deposition Method  

NASA Astrophysics Data System (ADS)

The present work is concerned on developing high sensitive and high performance SnO2-based gas sensors for detecting indoor air pollutant formaldehyde gas. The film was deposited on an alumina substrate using R.F. Induction Plasma Deposition technique. Physical properties of sensing films were examined by SEM, XRD method. The sensors showed high sensitivity to typical HCHO gas at an extremely low gas concentration of 20 parts-per-billion (ppb) with quick response and recovery time at several minutes. The effect of the doping of various metallic additives on the gas-sensing properties and operating temperature dependency were also investigated in the work.

Shi, Liqin; Gao, Wei; Hasegawa, Yuki; Katsube, Teruaki; Nakano, Mamoru; Nakamura, Kiyozumi

185

Fabrication of thin film heat flux sensors  

NASA Technical Reports Server (NTRS)

Thin-film heat-flux sensors have been constructed in the form of arrays of thermocouples on upper and lower surfaces of an insulating layer, so that flux values are proportional to the temperature difference across the upper and lower surface of the insulation material. The sensor thermocouples are connected in thermopile arrangement, and the structure is patterned with photolithographic techniques. Both chromel-alumel and Pt-Pt/Rh thermocouples have been devised; the later produced 28 microvolts when exposed to the radiation of a 1000 C furnace.

Will, Herbert

1991-01-01

186

Thin film mixed potential sensors  

DOEpatents

A mixed potential sensor for oxidizable or reducible gases and a method of making. A substrate is provided and two electrodes are formed on a first surface of the substrate, each electrode being formed of a different catalytic material selected to produce a differential voltage between the electrodes from electrochemical reactions of the gases catalyzed by the electrode materials. An electrolytic layer of an electrolyte is formed over the electrodes to cover a first portion of the electrodes from direct exposure to the gases with a second portion of the electrodes uncovered for direct exposure to the gases.

Garzon, Fernando H. (Santa Fe, NM); Brosha, Eric L. (Los Alamos, NM); Mukundan, Rangachary (Santa Fe, NM)

2007-09-04

187

Thin-film spectroscopic sensor  

DOEpatents

There is disclosed an integrated spectrometer for chemical analysis by evanescent electromagnetic radiation absorption in a reaction volume. The spectrometer comprises a noninteractive waveguide, a substrate, an entrance grating and an exit grating, an electromagnetic radiation source, and an electromagnetic radiation sensing device. There is further disclosed a chemical sensor to determine the pressure and concentration of a chemical species in a mixture comprising an interactive waveguide, a substrate, an entrance grating and an exit grating, an electromagnetic radiation source, and an electromagnetic radiation sensing device.

Burgess, Jr., Lloyd W. (Seattle, WA); Goldman, Don S. (Richland, WA)

1992-01-01

188

SiC-Based Gas Sensors.  

National Technical Information Service (NTIS)

Electronic grade Silicon Carbide (SiC) is a ceramic material which can operate as a semiconductor at temperatures above 600 C. Recently, SiC semiconductors have been used in Schottky diode gas sensor structures. These sensors have been shown to be functio...

L. Y. Chen G. W. Hunter P. G. Neudeck D. Knight C. C. Liu Q. H. Wu

1997-01-01

189

Theory of gas sensors: response of an electrochemical sensor to multi-component gas mixtures  

Microsoft Academic Search

A first-principles model of the operation of an electrochemical metal oxide gas sensor had been previously used to analyze the response when the sensor was exposed to a simple gas mixture (e.g. O2\\/CO\\/CO2). Here, the model is extended to study the sensor response to a complex gas mixture containing two reducing gases e.g. O2\\/CO\\/CO2\\/H2\\/H2O. In a first version, it is

A. D. Brailsford; M. Yussouff; E. M. Logothetis

1996-01-01

190

Unsteady heat transfer from a thick hot-film sensor  

NASA Astrophysics Data System (ADS)

This study is aimed at developing numerical and analytical models of thick hot-film sensor that include thermal storage in the sensor. Transient conjugate heat transfer analysis is carried out with the unsteady surface element (USE) method. The temperature response of the sensor is determined from analysis of three bodies (air, hot film, and polymer substrate). The average temperature of the hot-film sensor is determined, with known heat flux input to the hot film and with known air velocity. This work, which involves steady airflow with transient heat transfer, is a first step toward transient airflow analysis of these sensors.

Park, Chong H.; Cole, Kevin D.

1994-10-01

191

Developing Multilayer Thin Film Strain Sensors With High Thermal Stability  

NASA Technical Reports Server (NTRS)

A multilayer thin film strain sensor for large temperature range use is under development using a reactively-sputtered process. The sensor is capable of being fabricated in fine line widths utilizing the sacrificial-layer lift-off process that is used for micro-fabricated noble-metal sensors. Tantalum nitride films were optimized using reactive sputtering with an unbalanced magnetron source. A first approximation model of multilayer resistance and temperature coefficient of resistance was used to set the film thicknesses in the multilayer film sensor. Two multifunctional sensors were fabricated using multilayered films of tantalum nitride and palladium chromium, and tested for low temperature resistivity, TCR and strain response. The low temperature coefficient of resistance of the films will result in improved stability in thin film sensors for low to high temperature use.

Wrbanek, John D.; Fralick, Gustave C.; Gonzalez, Jose M., III

2006-01-01

192

Thin film hydrogen sensors: A materials processing approach  

NASA Astrophysics Data System (ADS)

Hydrogen (H2) is consumed and produced in large quantities by chemical, petroleum, plastic, space and glass industries. Detection and quantitative estimation of H2 in a reliable and efficient manner is of great value in these applications, not only from a safety stand point but also economically beneficial. Hence the requirement for a simple but efficient hydrogen sensor. The simplest hydrogen sensors are based on monitoring changes in electrical properties of group VIII transition metals, especially palladium (Pd). Hydrogen adsorbs on Pd surface and diffuses into its bulk altering its electrical and optical properties. This variation is used to detect/estimate hydrogen in the ambience. However, at high hydrogen concentrations palladium undergoes a phase change. This causes an expansion of the lattice---a problem for fabricating reliable sensors using this metal. This problem was overcome by alloying palladium with nickel. Currently, sensors made from palladium alloy thin films (resistors and FET's) can detect/estimate hydrogen from ppm to 100% concentrations. However, these sensors are affected by the total gas pressure and other gases like carbon monoxide (CO), sulfur dioxide (SO 2), hydrogen sulfide (H2S). This work, for most part deals with resistors (chemiresistors). Resistors estimate hydrogen by correlating the change in resistance to the hydrogen concentration. Magnetron sputtering enables the deposition of films of different compositions and morphology. In this work, Pd and Pd/Ni alloy thin films resistors were fabricated by sputtering. Morphology was seen to have a significant effect on the hydrogen sensing property of these films. In presence of CO the response of these sensors are extremely sluggish, however by employing SiO2 barrier layer the response was greatly improved. It was noted that despite the sluggish response, the signal from the chemiresistors did saturate to same level as seen in absence of CO from gas mixture; contrary to the earlier results. Also the geometry of the resistors did not have any effect on the sensor sensitivity or response. Mass spectroscopy and ion energy distribution function (IEDF) analysis are important tools for characterizing processing plasmas. In this work, the sputter discharges were studied using energy and quadrupole mass spectrometer from Hiden. The IEDF of pulsed DC sputter discharges indicated a higher energy peak (˜65eV) and a broad distribution in addition to the low energy peak (˜5eV). The high energy peak was absent from the DC sputter discharge. This high energy peak was correlated to the pulsing of the DC source and was found to be independent of the target material.

Jayaraman, Raviprakash

193

A Phenomenological Model of Industrial Gas Sensors  

Microsoft Academic Search

Gas sensors are widely used in industry for applications ranging from air-to-fuel ratio control in combustion processes, including those in automotive engines and industrial furnaces, to leakage detection of inflammable and toxic gases. This presentation reports on a model to describe the response of typical electrochemical solid state gas sensors in environments of air (80% N2 and 20% O_2) and

J. T. Woestman; E. M. Logothetis; M. D. Shane; A. D. Brailsford

1997-01-01

194

Diamond diode-based chemical gas sensors  

NASA Astrophysics Data System (ADS)

The successful utilization of microelectronic-based gas sensors (MOS Capacitor, MOSFET, MS, and MIS diodes) in many practical applications such as automotive, aeronautical, commercial, and environmental has not been achieved due to the limited operating temperature range of Si and GaAs semiconductors (less than 200sp°C). Present development in the diamond technology provides an opportunity to address this problem. Along with its well known physical and optical properties, the superior semiconductor properties of diamond over Si, GaAs, and SiC (higher breakdown voltage, energy band gap, carrier mobility, and thermal conductivity) are useful for gas sensor applications. We have developed a novel family of diamond-based chemical gas sensors for the detection of hydrogen, oxygen and carbon monoxide at a higher operating temperature range than currently possible with Si- and GaAs-based microelectronic gas sensors. The new devices were fabricated in the form of a Pd/i-diamond/psp+-diamond MIS structure for the detection hydrogen and a Pt/SnOsb{x}/i-diamond/psp+-diamond CAIS structure for the detection of oxygen and carbon monoxide. Sensor performances have been investigated over a wide temperature range (22sp° C{-}400sp° C). The gas sensitivity of the devices have been found to be large, fast, selective, repeatable, and reproducible. Detection mechanisms of the sensors have been developed. The hydrogen detection mechanism of the diamond-based MIS device is due to hydrogen dipole formation at the Pd/i-diamond interface and a subsequent change in the voltage distribution across the junction. The oxygen and carbon monoxide sensitivity of the CAIS device is attributed to the modification of the oxygen vacancies in the SnOsb{x} layer and the subsequent change in the voltage drop across the oxide. The current transport mechanisms of the sensors have been studied and gas adsorption effects on sensor parameters have been modeled. The current conduction mechanism of the sensors is Space Charge Limited, distinctively different from Si- and GaAs-based diodes. While no significant change was observed on the ideality factor, a change in the barrier height and tunneling factor of the sensors was found upon gas adsorption. The findings of this study form the basis for the utilization of microelectronic devices in wide range of gas sensor applications, requiring large sensitivity, fast, repeatable, and reproducible response, wider operating temperature range, and stability in harsh environments. Furthermore, this study contributes a fundamental knowledge in the operating principles and sensing mechanisms of the high temperature-tolerant microelectronic gas sensors.

Gurbuz, Yasar

195

Ionization gas sensor using aligned multiwalled carbon nanotubes (MWCNTs) array  

Microsoft Academic Search

Carbon nanotubes (CNTs) have drawn a lot of interest as the sensing element in sensor technology because of their unique electronic properties and remarkable mechanical properties. CNTs' extremely high surface-to-volume ratio makes it a very good candidate for the adsorption of gas molecules. Gas sensors are divided into two types, namely; physical gas sensors and chemical gas sensors. In the

Atieh Ranjbar Kermany; Norani Muti Mohamed; B. S. M. Singh

2010-01-01

196

Integrated Microfluidic Gas Sensors for Water Monitoring  

NASA Technical Reports Server (NTRS)

A silicon-based microhotplate tin oxide (SnO2) gas sensor integrated into a polymer-based microfluidic system for monitoring of contaminants in water systems is presented. This device is designed to sample a water source, control the sample vapor pressure within a microchannel using integrated resistive heaters, and direct the vapor past the integrated gas sensor for analysis. The sensor platform takes advantage of novel technology allowing direct integration of discrete silicon chips into a larger polymer microfluidic substrate, including seamless fluidic and electrical interconnects between the substrate and silicon chip.

Zhu, L.; Sniadecki, N.; DeVoe, D. L.; Beamesderfer, M.; Semancik, S.; DeVoe, D. L.

2003-01-01

197

Hydrogen gas sensor and method of manufacture  

DOEpatents

A sensor for measuring the pressure of hydrogen gas in a nuclear reactor, and method of manufacturing the same. The sensor comprises an elongated tube of hydrogen permeable material which is connected to a pressure transducer through a feedthrough tube which passes through a wall at the boundary of the region in which hydrogen is present. The tube is pressurized and flushed with hydrogen gas at an elevated temperature during the manufacture of the sensor in order to remove all gasses other than hydrogen from the device.

McKee, John M. (Hinsdale, IL)

1991-01-01

198

Sensor array for toxic gas detection  

DOEpatents

A portable instrument for use in the field in detecting and identifying a hazardous component in air or other gas including an array of small sensors which upon exposure to the gas from a pattern of electrical responses, a source of standard response patterns characteristic of various components, and microprocessor means for comparing the sensor-formed response pattern with one or more standard patterns to thereby identify the component on a display. The number of responses may be increased beyond the number of sensors by changing the operating voltage, temperature or other condition associated with one or more sensors to provide a plurality of responses from each of one or more of the sensors. In one embodiment, the instrument is capable of identifying anyone of over 50-100 hazardous components.

Stetter, Joseph R. (Naperville, IL); Zaromb, Solomon (Hinsdale, IL); Penrose, William R. (Naperville, IL)

1987-01-01

199

Resistive Oxygen Gas Sensors for Harsh Environments  

PubMed Central

Resistive oxygen sensors are an inexpensive alternative to the classical potentiometric zirconia oxygen sensor, especially for use in harsh environments and at temperatures of several hundred °C or even higher. This device-oriented paper gives a historical overview on the development of these sensor materials. It focuses especially on approaches to obtain a temperature independent behavior. It is shown that although in the past 40 years there have always been several research groups working concurrently with resistive oxygen sensors, novel ideas continue to emerge today with respect to improvements of the sensor response time, the temperature dependence, the long-term stability or the manufacture of the devices themselves using novel techniques for the sensitive films. Materials that are the focus of this review are metal oxides; especially titania, titanates, and ceria-based formulations.

Moos, Ralf; Izu, Noriya; Rettig, Frank; Reiss, Sebastian; Shin, Woosuck; Matsubara, Ichiro

2011-01-01

200

Graphene nanomesh as highly sensitive chemiresistor gas sensor.  

PubMed

Graphene is a one atom thick carbon allotrope with all surface atoms that has attracted significant attention as a promising material as the conduction channel of a field-effect transistor and chemical field-effect transistor sensors. However, the zero bandgap of semimetal graphene still limits its application for these devices. In this work, ethanol-chemical vapor deposition (CVD) of a grown p-type semiconducting large-area monolayer graphene film was patterned into a nanomesh by the combination of nanosphere lithography and reactive ion etching and evaluated as a field-effect transistor and chemiresistor gas sensors. The resulting neck-width of the synthesized nanomesh was about ?20 nm and was comprised of the gap between polystyrene (PS) spheres that was formed during the reactive ion etching (RIE) process. The neck-width and the periodicities of the graphene nanomesh (GNM) could be easily controlled depending on the duration/power of the RIE and the size of the PS nanospheres. The fabricated GNM transistor device exhibited promising electronic properties featuring a high drive current and an I(ON)/I(OFF) ratio of about 6, significantly higher than its film counterpart. Similarly, when applied as a chemiresistor gas sensor at room temperature, the graphene nanomesh sensor showed excellent sensitivity toward NO(2) and NH(3), significantly higher than their film counterparts. The ethanol-based graphene nanomesh sensors exhibited sensitivities of about 4.32%/ppm in NO(2) and 0.71%/ppm in NH(3) with limits of detection of 15 and 160 ppb, respectively. Our demonstrated studies on controlling the neck width of the nanomesh would lead to further improvement of graphene-based transistors and sensors. PMID:22931286

Paul, Rajat Kanti; Badhulika, Sushmee; Saucedo, Nuvia M; Mulchandani, Ashok

2012-10-01

201

Integrated Micro-Machined Hydrogen Gas Sensor. Final Report  

SciTech Connect

This report details our recent progress in developing novel MEMS (Micro-Electro-Mechanical Systems) based hydrogen gas sensors. These sensors couple novel thin films as the active layer on a device structure known as a Micro-HotPlate. This coupling has resulted in a gas sensor that has several unique advantages in terms of speed, sensitivity, stability and amenability to large scale manufacture. This Phase-I research effort was focused on achieving the following three objectives: (1) Investigation of sensor fabrication parameters and their effects on sensor performance. (2) Hydrogen response testing of these sensors in wet/dry and oxygen-containing/oxygen-deficient atmospheres. (3) Investigation of the long-term stability of these thin film materials and identification of limiting factors. We have made substantial progress toward achieving each of these objectives, and highlights of our phase I results include the demonstration of signal responses with and without oxygen present, as well as in air with a high level of humidity. We have measured response times of <0.5 s to 1% H{sub 2} in air, and shown the ability to detect concentrations of <200 ppm. These results are extremely encouraging and suggest that this technology has substantial potential for meeting the needs of a hydrogen based economy. These achievements demonstrate the feasibility of using micro-hotplates structures in conjunction with palladium+coated metal-hydride films for sensing hydrogen in many of the environments required by a hydrogen based energy economy. Based on these findings, they propose to continue and expand the development of this technology in Phase II.

Frank DiMeo, Jr.

2000-10-02

202

Automotive application of sol–gel TiO 2 thin film-based sensor for lambda measurement  

Microsoft Academic Search

We report on the preparation and characterization of titanium dioxide thin film gas sensor devices for application in lambda measurement. The sensor responses to different oxygen concentrations have been analyzed. Moreover, according to a computing software that simulates the composition of exhaust gases for different ? values, we exposed the sensors to different complex mixtures of exhaust gases, calibrating in

L. Francioso; D. S. Presicce; A. M. Taurino; R. Rella; P. Siciliano; A. Ficarella

2003-01-01

203

Study of poly (3-hexylthiophene) conducting polymer thin film micro-sensor for hydrazine vapor detection  

NASA Astrophysics Data System (ADS)

This dissertation discussed the construction and investigation of a poly (3-hexylthiophene) conducting polymer based thin film micro-sensor for a real-time detection of hydrazine vapor at ambient pressure. A type of low cost, small size, passive poly (3-hexylthiophene) thin film micro-sensor was designed and fabricated. The micro-sensor platform consisted of a rectangular shaped inert substrate and gold interdigited electrode pairs. A layer of poly (3-hexylthiophene) thin film was coated onto the sensor platform using a spin coating method, and nitrosonium hexafluorophosphate (NOPF6) was used to dope the poly (3-hexylthiophene) thin film to increase its electrical conductivity and form the finished sensor. The basic responses of the sensor to hydrazine vapor were experimentally investigated. The primary results showed that the sensor responded to hydrazine vapor in less than a few seconds; attained orders of magnitude change in normalized resistance during hydrazine exposure, and was not easily saturated. The interaction between the hydrazine gas molecules and doped poly (3-hexylthiophene) thin film was studied. The plausible mechanism was determined as: Charge carriers inside the doped poly (3-hexylthiophene) thin film were depleted during the oxidation-reduction chemical reaction between the hydrazine vapor and polymer film, resulting a reduction in the polymer film's electrical conductivity. Experiments were also conducted to find out the effects of hydrazine concentration, poly (3-hexylthiophene) thin film thickness, sensor storage time, environment temperature, and environment humidity on the sensor's performance. The response rate of the sensor under different sensing conditions was calculated and discussed. A diffusion-reaction model was applied to simulate the interaction between hydrazine molecules and doped poly (3-hexylthiophene) thin film. The profiles of hydrazine gas diffusion and positive charge carrier neutralization in the polymer film were obtained. Generally good agreement was achieved between the numerical simulation and experimental results which confirmed that the process was mainly controlled by the gas diffusion and chemical reaction. The positive correlation observed between computational and experimental data offers confidence in the prediction of sensor responses for different polymer film thicknesses and operation temperatures.

Yang, Hong

204

Room temperature gas sensitivity of ultrathin SnO2 films prepared from Langmuir-Blodgett film precursors  

NASA Astrophysics Data System (ADS)

The authors report the room temperature gas sensitivity of ultrathin SnO2 films prepared by thermal decomposition of multilayer Langmuir-Blodgett (LB) films. The SnO2 films, which are characterized by various spectroscopic techniques and electrical measurements, have been shown to sense ammonia gas at room temperature with fast response and recovery. The presence of a large number of surface states in the ultrathin SnO2 film is responsible for the room temperature gas sensitivity. Present results demonstrate the potential of LB technique to fabricate high quality ultrathin oxide films useful for sensor applications.

Choudhury, Sipra; Betty, C. A.; Girija, K. G.; Kulshreshtha, S. K.

2006-08-01

205

A room temperature HSGFET ammonia sensor based on iridium oxide thin film  

Microsoft Academic Search

Gas-sensing properties of hybrid suspended gate FET (HSGFET) sensor containing iridium oxide as sensitive layer are reported in this paper. The sensor response to NH3 and H2 was measured. We obtained a non-amplified signal of 70mV for 50ppm of ammonia and no signal to hydrogen even for 10,000ppm. Further, the gas-sensing properties of thin film of iridium oxide has been

A. Karthigeyan; R. P. Gupta; K. Scharnagl; M. Burgmair; S. K. Sharma; I. Eisele

2002-01-01

206

High resolution gas volume change sensor  

SciTech Connect

Changes of gas quantity in a system can be measured either by measuring pressure changes or by measuring volume changes. As sensitive pressure sensors are readily available, pressure change is the commonly used technique. In many physiologic systems, however, buildup of pressure influences the gas exchange mechanisms, thus changing the gas quantity change rate. If one wants to study the gas flow in or out of a biological gas pocket, measurements need to be done at constant pressure. In this article we present a highly sensitive sensor for quantitative measurements of gas volume change at constant pressure. The sensor is based on optical detection of the movement of a droplet of fluid enclosed in a capillary. The device is easy to use and delivers gas volume data at a rate of more than 15 measurements/s and a resolution better than 0.06 {mu}l. At the onset of a gas quantity change the sensor shows a small pressure artifact of less than 15 Pa, and at constant change rates the pressure artifact is smaller than 10 Pa or 0.01% of ambient pressure.

Dirckx, Joris J. J.; Aernouts, Jef E. F.; Aerts, Johan R. M. [Laboratory of Biomedical Physics, University of Antwerp, Groenenborgerlaan 171, Antwerp, Flanders B-2020 (Belgium)

2007-05-15

207

Diamond Thin Film Temperature and Heat-Flux Sensors.  

National Technical Information Service (NTIS)

Diamond film temperature and heat-flux sensors are developed using a technology compatible with silicon integrated circuit processing. The technology involves diamond nucleation, patterning, doping, and metallization. Multi-sensor test chips were designed...

M. Aslam G. S. Yang A. Masood R. Fredricks

1995-01-01

208

Biomaterial based sulphur di oxide gas sensor  

NASA Astrophysics Data System (ADS)

Biomaterials are getting importance in the present research field of sensors. In this present paper performance of biomaterial based gas sensor made of gum Arabica and garlic extract had been studied. Extract of garlic clove with multiple medicinal and chemical utility can be proved to be useful in sensing Sulphur di Oxide gas. On exposure to Sulphur di Oxide gas the material under observation suffers some temporary structural change, which can be observed in form of amplified potentiometric change through simple electronic circuitry. Exploiting this very property a potentiometric gas sensor of faster response and recovery time can be designed. In this work sensing property of the said material has been studied through DC conductance, FTIR spectrum etc.

Ghosh, P. K.; Sarkar, A.

2013-06-01

209

Thin Film Heat Flux Sensors: Design and Methodology  

NASA Technical Reports Server (NTRS)

Thin Film Heat Flux Sensors: Design and Methodology: (1) Heat flux is one of a number of parameters, together with pressure, temperature, flow, etc. of interest to engine designers and fluid dynamists, (2) The measurement of heat flux is of interest in directly determining the cooling requirements of hot section blades and vanes, and (3)In addition, if the surface and gas temperatures are known, the measurement of heat flux provides a value for the convective heat transfer coefficient that can be compared with the value provided by CFD codes.

Fralick, Gustave C.; Wrbanek, John D.

2013-01-01

210

Selectivity improvement of semi-conducting gas sensors by selective filter for atmospheric pollutants detection  

Microsoft Academic Search

The monitoring of atmospheric pollution using chemical gas sensors is a challenge due to the lack of selectivity of most existing devices. However, their performances can be improved using filtering films achieving the separation or the removal of some gases. This study is focused on the detection of carbon monoxide and of oxidant pollutants (nitrogen dioxide and ozone) by sensors

J. P. Viricelle; A. Pauly; L. Mazet; J. Brunet; M. Bouvet; C. Varenne; C. Pijolat

2006-01-01

211

Miniaturized gas ionization sensors using carbon nanotubes  

NASA Astrophysics Data System (ADS)

Gas sensors operate by a variety of fundamentally different mechanisms. Ionization sensors work by fingerprinting the ionization characteristics of distinct gases, but they are limited by their huge, bulky architecture, high power consumption and risky high-voltage operation. Here we report the fabrication and successful testing of ionization microsensors featuring the electrical breakdown of a range of gases and gas mixtures at carbon nanotube tips. The sharp tips of nanotubes generate very high electric fields at relatively low voltages, lowering breakdown voltages several-fold in comparison to traditional electrodes, and thereby enabling compact, battery-powered and safe operation of such sensors. The sensors show good sensitivity and selectivity, and are unaffected by extraneous factors such as temperature, humidity, and gas flow. As such, the devices offer several practical advantages over previously reported nanotube sensor systems. The simple, low-cost, sensors described here could be deployed for a variety of applications, such as environmental monitoring, sensing in chemical processing plants, and gas detection for counter-terrorism.

Modi, Ashish; Koratkar, Nikhil; Lass, Eric; Wei, Bingqing; Ajayan, Pulickel M.

2003-07-01

212

Ultra-Low-Power MEMS Selective Gas Sensors  

NASA Technical Reports Server (NTRS)

This innovation is a system for gas sensing that includes an ultra-low-power MEMS (microelectromechanical system) gas sensor, combined with unique electronic circuitry and a proprietary algorithm for operating the sensor. The electronics were created from scratch, and represent a novel design capable of low-power operation of the proprietary MEMS gas sensor platform. The algorithm is used to identify a specific target gas in a gas mixture, making the sensor selective to that target gas.

Stetter, Joseph

2012-01-01

213

Recognizing indoor formaldehyde in binary gas mixtures with a micro gas sensor array and a neural network  

NASA Astrophysics Data System (ADS)

Low-concentration formaldehyde (HCHO) together with ethanol/toluene/acetone/?-pinene (as an interference gas of HCHO) is detected with a micro gas sensor array, composed of eight tin oxide (SnO2) thin film gas sensors with Au, Cu, Pt or Pd metal catalysts. The characteristics of the multi-dimensional signals from the eight sensors are evaluated. A multilayer neural network with an error backpropagation (BP) learning algorithm, plus the principal component analysis (PCA) technique, is implemented to recognize these indoor volatile organic compounds (VOC). The results show that the micro gas sensor array, plus the multilayer neural network, is very effective in recognizing 0.06 ppm HCHO in single gas component and in binary gas mixtures, toluene/ethanol/?-pinene with small relative error.

Lv, Pin; Tang, Zhenan; Wei, Guangfen; Yu, Jun; Huang, Zhengxing

2007-09-01

214

Thin film heat flux sensor for Space Shuttle Main Engine turbine environment  

NASA Technical Reports Server (NTRS)

The Space Shuttle Main Engine (SSME) turbine environment stresses engine components to their design limits and beyond. The extremely high temperatures and rapid temperature cycling can easily cause parts to fail if they are not properly designed. Thin film heat flux sensors can provide heat loading information with almost no disturbance of gas flows or of the blade. These sensors can provide steady state and transient heat flux information. A thin film heat flux sensor is described which makes it easier to measure small temperature differences across very thin insulating layers.

Will, Herbert

1991-01-01

215

Optical Sensors Based on Single Arm Thin Film Waveguide Interferometer  

NASA Technical Reports Server (NTRS)

Single-arm double-mode double-order optical waveguide interferometer utilizes interference between two propagating modes of different orders. Sensing effect results from the change in propagation conditions of the modes caused by the environment. The waveguide is made as an open asymmetric slab structure containing a dye-doped polymer film onto a fused quartz substrate. It is more sensitive to the change of environment than its conventional polarimetric analog using orthogonal modes (TE and TM) of the same order. The sensor still preserves the option of operating in polarimetric regime using a variety of mode combinations such as TE(sub 0)/TM(sub 0) (conventional), TE(sub 0)/TM(sub 1), TE(sub 1)/TM(sub 0), or TE(sub 1)/TM(sub 1) but can also work in nonpolarimetric regime using combinations TE(sub 0)/TM(sub 1) or TE(sub 0)/TM(sub 1). Utilization of different mode combinations simultaneously makes the device more versatile. Application of the sensor to gas sensing is based on doping polymer film with an organic indicator dye sensitive to a particular gas. Change of optical absorption spectrum of the dye caused by the gaseous pollutant results change of the reactive index of the dye-doped polymer film that can be detected by the sensor. As an indicator dyes, we utilize Bromocresol Purple doped into polymer poly(methyl) methacrylate, which shows a reversible growth of the absorption peak neat 600 nm after exposure to wet ammonia. We have built a breadboard prototype of the sensor with He-Ne laser as a light source and with a single mode fiber input and a multimode fiber output. The prototype showed sensitivity to temperature change of the order of 2 C per one full oscillation of the signal. The sensitivity of the sensor to the presence of wet ammonia is 200 ppm per one full oscillation of the signal. The further improvements include switching to a longer wavelength laser source (750-nm semiconductor laser), substitution of poly(methyl) methacrylate with hydrophilic high-temperature polyimide, and increase the doping rate of indicator dye. All these improvements are expected to bring sensitivity to 10 ppm of ammonia per one full oscillation of signal independent on the humidity of ambient air. The proposed sensor can be used as a robust and inexpensive stand-alone instrument for continuous environment pollution monitoring.

Sarkisov, S. S.; Diggs, D.; Curley, M.; Adamovsky, Grigory (Technical Monitor)

2001-01-01

216

A Phenomenological Model of Industrial Gas Sensors  

NASA Astrophysics Data System (ADS)

Gas sensors are widely used in industry for applications ranging from air-to-fuel ratio control in combustion processes, including those in automotive engines and industrial furnaces, to leakage detection of inflammable and toxic gases. This presentation reports on a model to describe the response of typical electrochemical solid state gas sensors in environments of air (80% N2 and 20% O_2) and one reducing species such as CO, H2 or CH_4. The goal of the model is to predict the time-dependent sensor output resulting from a time-dependent gas composition. Through a set of coupled differential equations, the model accounts for the flow of the gases into the sensor, their diffusion through a porous spinel coating, their adsorption/desorption on/off a catalytic electrode and their redox reaction on the electrode. The solution of these equations provides an oxygen adatom concentration on the electrode surface. This oxygen concentration is used in the Nernst equation to determine an instantaneous sensor emf and a first order filter is user to account for the time delay associated with the emf generation processes. The model was applied to the operation of an automotive oxygen sensor exposed to mixtures of O2 and CO in N2 and mixtures of O2 and H2 in N_2. Good agreement was found with experimental results under both steady state and dynamic operating conditions.

Woestman, J. T.; Logothetis, E. M.; Shane, M. D.; Brailsford, A. D.

1997-08-01

217

Four-Channel QCA Using Mesoporous Silica Films for Gas Sensing Applications  

Microsoft Academic Search

A four-channel quartz crystal microbalance array (QCA) coated with silica hybrid films is tested as a gas sensor to identify and quantify target analytes. Plasma calcined mesoporous silica films have been used to form hybrids for gas sensing applications. Silica hybrids are obtained by incorporating various receptor molecules in the porous network through physiosorption and\\/or chemical bonding between the silica

Alagappan Palaniappan; Xiaodi Su; Francis E. H. Tay

2006-01-01

218

ZnO thin film sensor  

Microsoft Academic Search

The electrical and gas sensing properties of chemically deposited zinc oxide (ZnO) films were investigated. Two activation energy values, 0.3 eV and 0.8–0.9 eV, were determined in the temperature range 300–400 K which are attributed to oxygen vacancy (VO) donor and heat of chemisorption of the O2? species. The adsorption of oxygen on ZnO leads to a stable and highly

P. Mitra; A. P. Chatterjee; H. S. Maiti

1998-01-01

219

Temperature dependence of gas sensing behaviour of TiO2 doped PANI composite thin films  

NASA Astrophysics Data System (ADS)

In the present work we have reported the effect of temperature on the gas sensing properties of TiO2 doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and TiO2 doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline at low temperature. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature TiO2 doped PANI composite sensor shows higher response value and showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement.

Srivastava, Subodh; Sharma, S. S.; Sharma, Preetam; Sharma, Vinay; Rajura, Rajveer Singh; Singh, M.; Vijay, Y. K.

2014-04-01

220

Ultra-sensitive strain sensors based on piezoresistive nanographene films  

NASA Astrophysics Data System (ADS)

Graphene shows promise on strain sensor applications, but the piezoresistive sensitivity of perfect graphene is low due to its weak electrical conductivity response upon structural deformation. In this paper, we used nanographene films for ultra-sensitive strain sensors. The piezoresistive sensitivity of nanographene films with different thicknesses and conductivities was systematically investigated and a nearly inverse proportional correlation was found. A gauge factor over 300, the highest so far for graphene-based strain sensors, was achieved. A charge tunneling model was used to explain the piezoresistive characteristics of nanographene films, which indicates our results provide a different rout toward ultra-sensitive strain sensors.

Zhao, Jing; He, Congli; Yang, Rong; Shi, Zhiwen; Cheng, Meng; Yang, Wei; Xie, Guibai; Wang, Duoming; Shi, Dongxia; Zhang, Guangyu

2012-08-01

221

Development of High Temperature Gas Sensor Technology  

NASA Technical Reports Server (NTRS)

The measurement of engine emissions is important for their monitoring and control. However, the ability to measure these emissions in-situ is limited. We are developing a family of high temperature gas sensors which are intended to operate in harsh environments such as those in an engine. The development of these sensors is based on progress in two types of technology: (1) The development of SiC-based semiconductor technology; and (2) Improvements in micromachining and microfabrication technology. These technologies are being used to develop point-contact sensors to measure gases which are important in emission control especially hydrogen, hydrocarbons, nitrogen oxides, and oxygen. The purpose of this paper is to discuss the development of this point-contact sensor technology. The detection of each type of gas involves its own challenges in the fields of materials science and fabrication technology. Of particular importance is sensor sensitivity, selectivity, and stability in long-term, high temperature operation. An overview is presented of each sensor type with an evaluation of its stage of development. It is concluded that this technology has significant potential for use in engine applications but further development is necessary.

Hunter, Gary W.; Chen, Liang-Yu; Neudeck, Philip G.; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai; Zhou, Huan-Jun

1997-01-01

222

Micromachined metal oxide gas sensors: opportunities to improve sensor performance  

Microsoft Academic Search

This review deals with gas sensors combining a metal oxide based sensing layer and a substrate realized by using micromachining. It starts by giving an overview of the design principles and technology involved in the fabrication of micromachined substrates examining thermal and mechanical aspects. Both kinds of micromachined substrates, closed-membrane-type and the suspended-membrane-type, are discussed. The deposition of the sensing

Isolde Simon; Nicolae Bârsan; Michael Bauer; Udo Weimar

2001-01-01

223

Hydrogen-Sensing Response of Carbon-Nanotube Thin-Film Sensor with Pd Comb-Like Electrodes  

NASA Astrophysics Data System (ADS)

Hydrogen gas sensors based on single-walled carbon nanotube (SWCNT) films were fabricated with Pd comb-like electrodes. The SWCNT films were deposited by Mo/Co catalyst-assisted chemical vapor deposition using alcohol. The film included a high-density network of SWCNTs. The SWCNT film sensor showed a large conductance change and a fast response (20 s) upon exposure to 1% H2 gas in air at room temperature, while the conductance change was negligible for devices using Au electrodes.

Hayakawa, Yuki; Suda, Yoshiyuki; Hashizume, Tamotsu; Sugawara, Hirotake; Sakai, Yosuke

2007-04-01

224

A SF6 gas sensor using a dual track SAW device based on multi-wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

In this paper, we propose a sulfur hexafluoride (SF6) gas sensor using a dual track surface acoustic wave (SAW) device based on multi-wall carbon nanotubes (MWCNTs). The sensor consists of a dual track SAW device and MWCNT film sensitive to SF6 gas. The measurement acoustic track of the sensor is coated with an MWCNT film treated by an acid process which selectively absorbs SF6 gas, while the reference acoustic track is uncoated. Experimental results confirm that the SF6 gas sensor using a dual track SAW device based on multi-wall CNTs has good response characteristics to different concentrations of SF6 gas from 0.5 to 20 ppm. The sensor has good linearity and reproducibility, and its sensitivity is approximately 7.4 kHz ppm-1. Furthermore, the sensor has a smaller cross-sensitivity for SO2 and HF.

Wen, Changbao; Zhu, Changchun; Ju, Yongfeng; Liu, Li; Li, Wanlin; Yan, Dong; Xu, Hongke; Qiu, Yanzhang

2011-03-01

225

Construction of a Polyaniline Nanofiber Gas Sensor  

ERIC Educational Resources Information Center

The electrical properties of polyaniline changes by orders of magnitude upon exposure to analytes such as acids or bases, making it a useful material for detection of these analytes in the gas phase. The objectives of this lab are to synthesize different diameter polyaniline nanofibers and compare them as sensor materials. In this experiment…

Virji, Shabnam; Weiller, Bruce H.; Huang, Jiaxing; Blair, Richard; Shepherd, Heather; Faltens, Tanya; Haussmann, Philip C.; Kaner, Richard B.; Tolbert, Sarah H.

2008-01-01

226

Conduction Model of Metal Oxide Gas Sensors  

Microsoft Academic Search

Tin dioxide is a widely used sensitive material for gas sensors. Many research and development groups in academia and industry are contributing to the increase of (basic) knowledge\\/(applied) know-how. However, from a systematic point of view the knowledge gaining process seems not to be coherent. One reason is the lack of a general applicable model which combines the basic principles

Nicolae Barsan; Udo Weimar

2001-01-01

227

Colorimetric blood-gas monitoring sensors  

NASA Astrophysics Data System (ADS)

Colorimetric fiber optic sensors have been developed for measuring the pH and pCO2 of blood. These sensors are fabricated using a single 125 micrometers diameter optical fiber. Located at the distal end of the fiber is a capsule that contains a pH sensitive dye. The pCO2 sensor is fabricated from a pH sensor with the addition of a salt, bicarbonate, and the encapsulation with an ion impermeable gas permeable membrane. The distal end of the capsule is terminated with a reflective surface. The reflective surface can either be a polished metallic surface or, in this case, a TiO2 impregnated epoxy. The disposable sensor mates with an optical connector that contains two optical fibers of the same size as the disposable sensor. The two fibers within the optical cable provide a light path for both the antegrade and retrograde optical signals. These fibers are terminated at either the LED source or the detector. A prototype sensor assembly that incorporates the measurement of three physiological parameters (pH, pCO2, and sO2) has been demonstrated to fit within a standard 20 gauge arterial catheter, typically used for radial artery blood pressure monitoring, without significant damping of the blood pressure waveform. The pH sensor has a range of 6.9 - 7.8 with a precision of 0.01 pH units and the pCO2 sensor has a range of 15 - 95 mm Hg with a precision of 3 mm Hg. The long term drift pH drift is less than 0.01 pH unit per 8 hours and the pCO2 drift is less than 1 mm Hg per 8 hours. Sensor performance in the canine has demonstrated that the pH sensor is accurate to within +/- 0.03 pH units and the pCO2 sensor is accurate to within +/- 3 mm Hg when compared to a typical blood gas analyzer.

Proctor, Keith J.; Seifert, George P.

1993-05-01

228

Test Structures for Rapid Prototyping of Gas and Pressure Sensors  

NASA Technical Reports Server (NTRS)

A multi-project ceramic substrate was used in developing a gas sensor and pressure sensor. The ceramic substrate cantained 36 chips with six variants including sensors, process control monitors, and an interconnect ship. Tha gas sensor is being developed as an air quality monitor and the pressure gauge as a barometer.

Buehler, M.; Cheng, L. J.; Martin, D.

1996-01-01

229

Chemical sensor based on surface acoustic wave resonator using Langmuir-Blodgett film.  

PubMed

A one-port surface acoustic wave (SAW) resonators incorporating Langmuir-Blodgett (LB) films has been investigated. SAW sensors are one potential applications of SAW devices. Most of the work reported on SAW sensor concerns delay lines. In this paper we characterize the mass loading effects of one-port resonators by depositing successive monolayers of LB films onto the surface. A 90 MHz SAW gas-phase sensor has been fabricated on an ST cut quartz substrate, and one-port resonator configurations have been used as the sensing element. Ultra thin monolayers of arachidic acid and arachidic acid ethyl ester have been deposited using the LB method. The resonant frequencies and the Q values have been measured as sensor response. Experimental results show that the Q values and the resonant frequencies of the one-port SAW resonator vary with film mass loading on the SAW device surface. PMID:18244288

Nomura, T; Takebayashi, R; Saitoh, A

1998-01-01

230

Palladium Doped Tin Oxide Based Hydrogen Gas Sensors for Safety Applications  

NASA Astrophysics Data System (ADS)

Hydrogen is considered to be a hazardous gas since it forms a flammable mixture between 4 to 75% by volume in air. Hence, the safety aspects of handling hydrogen are quite important. For this, ideally, highly selective, fast response, small size, hydrogen sensors are needed. Although sensors based on different technologies may be used, thin-film sensors based on palladium (Pd) are preferred due to their compactness and fast response. They detect hydrogen by monitoring the changes to the electrical, mechanical or optical properties of the films. We report the development of Pd-doped tin-oxide based gas sensors prepared on thin ceramic substrates with screen printed platinum (Pt) contacts and integrated nicrome wire heaters. The sensors are tested for their performances using hydrogen-nitrogen gas mixtures to a maximum of 4% H2 in N2. The sensors detect hydrogen and their response times are less than a few seconds. Also, the sensor performance is not altered by the presence of helium in the test gas mixtures. By the above desired performance characteristics, field trials of these sensors have been undertaken. The paper presents the details of the sensor fabrication, electronic circuits, experimental setup for evaluation and the test results.

Kasthurirengan, S.; Behera, Upendra; Nadig, D. S.

2010-04-01

231

Ink-jet printed colorimetric gas sensors on plastic foil  

NASA Astrophysics Data System (ADS)

An all polymeric colorimetric gas sensor with its associated electronics for ammonia (NH3) detection targeting low-cost and low-power applications is presented. The gas sensitive layer was inkjet printed on a plastic foil. The use of the foil directly as optical waveguide simplified the fabrication, made the device more cost effective and compatible with large scale fabrication techniques, such as roll to roll processes. Concentrations of 500 ppb of NH3 in nitrogen with 50% of RH were measured with a power consumption of about 868 ?W in an optical pulsed mode of operation. Such sensors foresee applications in the field of wireless systems, for environmental and safety monitoring. The fabrication of the planar sensor was based on low temperature processing. The waveguide was made of PEN or PET foil and covered with an ammonia sensitive layer deposited by inkjet printing, which offered a proper and localized deposition of the film. The influence of the substrate temperature and its surface pretreatment were investigated to achieve the optimum deposition parameters for the printed fluid. To improve the light coupling from the light source (LED) to the detectors (photodiodes), polymeric micro-mirrors were patterned in an epoxy resin. With the printing of the colorimetric film and additive patterning of polymeric micro-mirrors on plastic foil, a major step was achieved towards the implementation of full plastic selective gas sensors. The combination with printed OLED and PPD would further lead to an integrated all polymeric optical transducer on plastic foil fully compatible with printed electronics processes.

Courbat, Jerome; Briand, Danick; de Rooij, Nico F.

2010-08-01

232

An electrothermal carbon nanotube gas sensor.  

PubMed

We show both gas pressure and species sensing capabilities based on the electrothermal effect of a multiwalled carbon nanotube (MWCNT). Upon exposure to gaseous environments, the resistance of a heated MWCNT is found to change following the conductive heat-transfer variances of gas molecules. To realize this mechanism, a suspended MWCNT is constructed by synthesis and assembly in localized chemical vapor deposition that is accomplished within seconds via real-time electrical feedback control. Vacuum pressure sensitivity and gas species differentiability are observed and analyzed. Such MWCNT electrothermal sensors are compact, fast and reversible in responses, and fully integratable with microelectronics. PMID:18001108

Kawano, Takeshi; Chiamori, Heather C; Suter, Marcel; Zhou, Qin; Sosnowchik, Brian D; Lin, Liwei

2007-12-01

233

Selective, pulsed CVD of platinum on microfilament gas sensors  

SciTech Connect

A post-processing, selective micro-chemical vapor deposition (``micro-CVD``) technology for the deposition of catalytic films on surface-micromachined, nitride-passivated polysilicon filaments has been investigated. Atmospheric pressure deposition of Pt on microfilaments was accomplished by thermal decomposition of Pt acetylacetonate; deposition occurs selectively only on those filaments which are electrically heated. Catalyst morphology, characterized by SEM, can be controlled by altering deposition time, filament temperature, and through the use of pulsed heating of the filament during deposition. Morphology plays an important role in determining the sensitivity of these devices when used as combustible gas sensors.

Manginell, R.P.; Smith, J.H.; Ricco, A.J.; Moreno, D.J.; Hughes, R.C. [Sandia National Labs., Albuquerque, NM (United States); Huber, R.J. [Utah Univ., Salt Lake City, UT (United States); Senturia, S.D. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1996-05-01

234

Graphene-based microfiber gas sensor  

NASA Astrophysics Data System (ADS)

In this paper, a novel graphene-based microfiber sensor is proposed and demonstrated for detection of gas concentration for the first time. As the complex refractive index (CRI) of graphene can be modulated by gas molecules in the surrounding environment, the propagating light along the graphene layer coupled by the microfiber would be altered to induce the attenuation of polarization mode intensity. Based on such a unique TE-polarization mode attenuation feature of graphene, experimental results showed that the acetone concentration can be measured accurately and quickly. Such an approach could open a window for realization of a variety of highly sensitive and fast gas or liquid sensors based on graphene, for wide applications in biological, medical and chemical fields.

Yao, Bai-Cheng; Wu, Yu; Chen, Yang; Liu, Xiu-Ping; Gong, Yuan; Rao, Yun-Jiang

235

Portable mid-infrared gas sensors: Development and applications  

Microsoft Academic Search

Several novel compact architectures of diode laser based absorption gas sensors have been developed, characterized and applied to real world applications. The motivation for this research has been the need to develop highly sensitive, selective and rapid response gas sensors that operate reliably in a non-laboratory environment. The gas sensors utilize rare earth doped fiber amplified near infrared diode lasers

Dirk Richter

2001-01-01

236

Porous Semiconductors: Advanced Material for Gas Sensor Applications  

Microsoft Academic Search

The present review article is devoted to the analysis of the problems related to the design of gas sensors based on porous semiconductors (PS). The peculiarities of the semiconductor porosification by anodic etching and the principles of gas sensor design based on porous semiconductors, including gas sensor construction and main operating characteristics, are considered in the article. It is shown

G. Korotcenkov; B. K. Cho

2010-01-01

237

Thin-Film Resistance Heat-Flux Sensors  

NASA Technical Reports Server (NTRS)

Thin-film heat-flux sensors of a proposed type would offer advantages over currently available thin-film heat flux sensors. Like a currently available thin-film heat-flux sensor, a sensor according to the proposal would be based on measurement of voltages related to the temperatures of thin metal films on the hotter and colder faces of a layer of an electrically insulating and moderately thermally conductive material. The heat flux through such a device is proportional to the difference between the temperatures and to the thermal conductivity of the layer. The advantages of the proposed sensors over the commercial ones would arise from the manner in which the temperature-related voltages would be generated and measured.

Fralick, Gustave C.; Wrbanek, John D.; Blaha, Charles A.

2005-01-01

238

Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring  

PubMed Central

Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition.

Fine, George F.; Cavanagh, Leon M.; Afonja, Ayo; Binions, Russell

2010-01-01

239

Fatigue crack monitoring with coupled piezoelectric film acoustic emission sensors  

NASA Astrophysics Data System (ADS)

Fatigue-induced cracking is a commonly seen problem in civil infrastructures reaching their original design life. A number of high-profile accidents have been reported in the past that involved fatigue damage in structures. Such incidences often happen without prior warnings due to lack of proper crack monitoring technique. In order to detect and monitor the fatigue crack, acoustic emission (AE) technique, has been receiving growing interests recently. AE can provide continuous and real-time monitoring data on damage progression in structures. Piezoelectric film AE sensor measures stress-wave induced strain in ultrasonic frequency range and its feasibility for AE signal monitoring has been demonstrated recently. However, extensive work in AE monitoring system development based on piezoelectric film AE sensor and sensor characterization on full-scale structures with fatigue cracks, have not been done. A lack of theoretical formulations for understanding the AE signals also hinders the use of piezoelectric film AE sensors. Additionally, crack detection and source localization with AE signals is a very important area yet to be explored for this new type of AE sensor. This dissertation presents the results of both analytical and experimental study on the signal characteristics of surface stress-wave induced AE strain signals measured by piezoelectric film AE sensors in near-field and an AE source localization method based on sensor couple theory. Based on moment tensor theory, generalized expression for AE strain signal is formulated. A special case involving the response of piezoelectric film AE sensor to surface load is also studied, which could potentially be used for sensor calibration of this type of sensor. A new concept of sensor couple theory based AE source localization technique is proposed and validated with both simulated and experimental data from fatigue test and field monitoring. Two series of fatigue tests were conducted to perform fatigue crack monitoring on large-scale steel test specimens using piezoelectric film AE sensors. Continuous monitoring of fatigue crack growth in steel structures is demonstrated in these fatigue test specimens. The use of piezoelectric film AE sensor for field monitoring of existing fatigue crack is also demonstrated in a real steel I-girder bridge located in Maryland. The sensor couple theory based AE source localization is validated using a limited number of piezoelectric film AE sensor data from both fatigue test specimens and field monitoring bridge. Through both laboratory fatigue test and field monitoring of steel structures with active fatigue cracks, the signal characteristics of piezoelectric film AE sensor have been studied in real-world environment.

Zhou, Changjiang

240

Sensor Array Devices Utilizing Nano-structured Metal-oxides for Hazardous Gas Detection  

NASA Astrophysics Data System (ADS)

Methane and carbon monoxide are two hazardous gases which require continuous monitoring by gas sensors in underground coal mines for explosion prevention and toxicity, respectively. This work explored implementing miniaturized gas sensors in this area to simultaneously detect both gases for benefits of increased portability and reduced power consumption of the chemiresistive gas sensor device. The focus of this research was to understand how the particle size, morphology, and microstructure of the metaloxide film affected the gas sensor performance to the two gases of interest on miniaturized gas sensor devices in the form of microhotplate platforms. This was done through three main research studies. The first was conducted by growing SnO2 nanowires from SnO 2 particles using an Au-catalyst. Growth conditions including temperature, time, and oxygen partial pressure were explored to determine the formation aspects of the SnO2 nanowires. Gas sensor studies were completed that provided evidence that the SnO2 nanowires increased detection to a fixed concentration of carbon monoxide compared to SnO2 particles without nano-structure formation. A second research study was performed to compare the gas sensor performance of SnO2 nanoparticles, hierarchical particles, and micron-size particles. The nanoparticles were developed into an ink and deposited via ink-jet printing on the microhotplate substrates to control the microstructure of the metal-oxide film. By preventing agglomeration of the nanoparticle film, the SnO2 nanoparticles displayed similar gas sensor performance to methane and carbon monoxide as the hierarchical particles. Both nano-structures had much higher gas sensor response than the micron-size particles which confirms the surface area of the metal-oxide film is critical for reaction of the analyte gas at the surface. The last research study presented in the dissertation describes an oxide nanoparticle array developed for detecting methane and carbon monoxide in the presence of one another. A design of experiments was constructed and principal component analysis was used for determining the optimum temperatures of the metal-oxide elements. A four element array was developed with the SnO 2 and TiO2 sensor elements able to detect methane concentrations of interest and the ZnO and NiO sensor elements able to detect the carbon monoxide concentrations. A linear based prediction model was developed and tested for accuracy and reproducibility of the model to a series of random gas concentrations.

Andio, Mark A.

241

Self-assembled thin film chemical sensors  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Current chemical sensors suffer from poor molecular specificity, sensitivity, and stability and seldom have the recovery properties needed for real-time monitoring applications. We have employed self-assembly techniques to covalently bond species- selective reagents directly to the surface of the transducer so that analyte/reagent chemistry occurs at the interface between the transducer and the media to be monitored. The use of self-assembling monolayer and -multilayer (SAM) techniques results in stable sensing elements with optimal specificity built in through the use of reagents that have been designed for molecular recognition. Moreover, self-assembly chemistry applied to oxide surfaces allows flexible means of transduction spanning optical, electrochemical, mass-loading, and conduction methods. The work conducted on this project focused on demonstration of the methodology and the application to selected organic vapors (aromatic compounds and halogenated hydrocarbons). We have been able to develop a series of surface acoustic wave (SAW) sensors that are specific for aromatic compounds and halogenated hydrocarbons based on self-assembled thin films of cyclodextrins and calixarenes. Monolayers of seven different cyclodextrins and clixarenes have been attached to SAW transducers and their response to several organic molecules in the vapor phase have been measured. This preliminary data confirms the efficacy of this approach for real- time monitoring of hydrocarbons.

Swanson, B.; Li, DeQuan

1996-11-01

242

Passive Chemiresistor Sensor Based on Iron (II) Phthalocyanine Thin Films for Monitoring of Nitrogen Dioxide  

NASA Astrophysics Data System (ADS)

In this dissertation, an alternate, new approach was investigated to produce a nonreversible, passive, iron (II) phthalocyanine (FePc) thin film sensor that does not require continuous power for operation. The sensor was manufactured using standard microelectronics fabrication procedures, with emphasis on low cost and sensor consistency. The sensor substrate consists of a gold interdigitated electrode pattern deposited on an oxidized silicon or quartz wafer. The FePc thin film is then vacuum sublimed over the interdigitated electrodes to form the finalized sensor. Different thicknesses and morphologies of FePc thin films were fabricated. Once sensor fabrication was accomplished, the general response, temperature dependence, concentration dependence, specificity, and longevity of FePc thin film sensors were investigated. To evaluate general sensor reponse, sensors were exposed to 100 ppm nitrogen dioxide in nitrogen, with a flow rate of 0.25 liters per minute (L/min), at the temperatures of -46, 20, and 71 °C. For each case, the resistance of the sensor decreased exponentially as a function of exposure duration and reached saturation within 25 minutes. The resistance decrease was measured to be four, three, and two orders of magnitude for the exposure temperatures of -46, 20, and 71 .C respectively. In these experiments, sub-zero temperature detection of nitrogen dioxide with FePc thin films was reported for the first time. It was found that the response at -46 °C was greater than at 20 or 71 °C. To evaluate temperature dependence, sensors were thermal cycled in the range of -50 to 80 °C, first under ultra-high purity nitrogen gas at 0.25 L/min, and then under 100 ppm nitrogen dioxide gas at 0.25 L/min. Intrinsic FePc film conductivity was measured by thermal cycling sensors under nitrogen gas. Extrinsic FePc film conductivity was measured by thermal cycling sensors under nitrogen dioxide gas. Results from these tests indicated that the temperature dependence of FePc thin film conductivity is described by the Arrhenius equation. Activation energies of 0.70 and 0.36 eV were measured for intrinsic and extrinsic conductivity respectively. To investigate the effects of sensor fabrication parameters, the film thickness, substrate type, and heat treatment effects were analyzed. FePc film thickness effects were investigated by fabricating sensors ranging from 50 to 450 nm in thickness. Observation of surface morphology under a scanning electron microscope (SEM) showed an evolution of increasing grain size and film roughness as film thickness increased. The 450 nm films have the largest grain size and surface roughness. They also form the best film-electrode contact. For substrate type analysis, FePc thin films simultaneously deposited on sensor substrates consisting of n-type oxidized silicon, p-type oxidized silicon, and quartz wafers were observed under SEM. Visual results show similar film morphologies. Electrical resistance levels under a continuous -50 to 80 °C thermal cycle under 0.1 L/min flowing nitrogen gas also indicated similar film conductivity values. In attempt to understand the sensor conductivity mechanism and to model sensor response, two theoretical models were developed. To determine the sensor conductivity mechanism, theoretical surface and bulk conductivity equations were derived for the sensor geometry. Comparison of measured resistance values with published metal-Pc conductivity values suggests that the bulk conductivity assumption yields comparable intrinsic values of 2.2 x 10-5 and 2.49 x 10-8 O-1m -1 at 80 and -50 °C respectively. Since a passive, integrating sensor inevitably approaches saturation, a sensor response model was developed for determining analyte concentrations based on the level of saturation. This passive response model was derived with reference to established equations on gas adsorption-desorption kinetics. Experimental sensor saturation data revealed that film conductivity is a power law of surface coverage. The passive sensing model also predicts a linear, proportional relation

Shu, John Hungjen

243

Thin sol–gel SiO 2–SnO x –AgO y films for low temperature ammonia gas sensor  

Microsoft Academic Search

Thin SiO2–SnOx–AgOy films were prepared, up to 60–100nm thick, by means of the sol–gel technology and characterized by a variety of analytical techniques. It is shown that the films have an amorphous structure with an inclusion of crystallites of Ag and Sn oxides. The conductance of the films is rather sensitive to the presence of NH3 impurity in air at

V. V. Petrov; T. N. Nazarova; A. N. Korolev; N. F. Kopilova

2008-01-01

244

Photonic crystals enable infrared gas sensors  

NASA Astrophysics Data System (ADS)

Sensors of trace gases are of enormous importance to diverse fields such as environmental protection, household safety, homeland security, bio-hazardous material identification, meteorology and industrial environments. The gases of interest include CO for home environments, CO2 for industrial and environment applications and toxic effluents such as SO2, CH4, NO for various manufacturing environments. We propose a new class of IR gas sensors, where the enabling technology is a spectrally tuned metallo-dielectric photonic crystal. Building both the emitting and sensing capabilities on to a single discrete element, Ion Optics" infrared sensorchip brings together a new sensor paradigm to vital commercial applications. Our design exploits Si-based suspended micro-bridge structures fabricated using conventional photolithographic processes. Spectral tuning, control of bandwidth and direction of emission were accomplished by specially designed metallo-dielectric photonic crystal surfaces.

Puscasu, Irina; Johnson, Edward A.; Pralle, Martin U.; McNeal, Mark P.; Daly, James T.; Greenwald, Anton C.

2004-10-01

245

In2O3-based micro gas sensor for detecting NO x gases  

NASA Astrophysics Data System (ADS)

In this study, NO x micro gas sensors for monitoring the indoor atmosphere of automobile were fabricated using MEMS (microelectromechanical system) technology and a sol-gel process. The sensing electrode and micro heater were designed to have a co-planar typed structure in a Pt thin film layer. The thermal characteristics of a micro heater array were analyzed using a finite element method (FEM). The chip size of the gas sensor was approximately 2 mm × 2 mm. Indium oxide as a sensing material for NO x gas was synthesized by a sol-gel process with indium isopropoxide as a precursor. Field emission Scanning electron microscopy and x-ray diffraction showed that particle size of the synthesized In2O3 was approximately 17-45 nm. The maximum gas sensitivity as the relative resistance ( R s = R gas / R air ) was observed at 275°C with a value of 8.0 at 1 ppm NO2 gas. The response (80% saturation) and recovery times were within 1 min. The sensing properties of NO2 gas exhibited linear behavior with increasing gas concentration. The sensing mechanism of the gas sensor was explained by the variations in the electron depletion layers and the adsorption of gas molecules on the In2O3 particle surface. These results suggest that in the future, MEMS-based gas sensors can be used as automotive-exhaust-gas sensors.

Kim, Bum-Joon; Song, In-Gyu; Kim, Jung-Sik

2014-03-01

246

Modular Analytical Multicomponent Analysis in Gas Sensor Aarrays  

PubMed Central

A multi-sensor system is a chemical sensor system which quantitatively and qualitatively records gases with a combination of cross-sensitive gas sensor arrays and pattern recognition software. This paper addresses the issue of data analysis for identification of gases in a gas sensor array. We introduce a software tool for gas sensor array configuration and simulation. It concerns thereby about a modular software package for the acquisition of data of different sensors. A signal evaluation algorithm referred to as matrix method was used specifically for the software tool. This matrix method computes the gas concentrations from the signals of a sensor array. The software tool was used for the simulation of an array of five sensors to determine gas concentration of CH4, NH3, H2, CO and C2H5OH. The results of the present simulated sensor array indicate that the software tool is capable of the following: (a) identify a gas independently of its concentration; (b) estimate the concentration of the gas, even if the system was not previously exposed to this concentration; (c) tell when a gas concentration exceeds a certain value. A gas sensor data base was build for the configuration of the software. With the data base one can create, generate and manage scenarios and source files for the simulation. With the gas sensor data base and the simulation software an on-line Web-based version was developed, with which the user can configure and simulate sensor arrays on-line.

Chaiyboun, Ali; Traute, Rudiger; Kiesewetter, Olaf; Ahlers, Simon; Muller, Gerhard; Doll, Theodor

2006-01-01

247

Multifrequency interrogation of nanostructured gas sensor arrays: a tool for analyzing response kinetics.  

PubMed

This paper presents a unique perspective on enhancing the physicochemical mechanisms of two distinct highly sensitive nanostructured metal oxide micro hot plate gas sensors by utilizing an innovative multifrequency interrogation method. The two types of sensors evaluated here employ an identical silicon transducer geometry but with a different morphological structure of the sensitive film. While the first sensing film consists of self-ordered tungsten oxide nanodots, limiting the response kinetics of the sensor-chemical species pair only to the reaction phenomena occurring at the sensitive film surface, the second modality is a three-dimensional array of tungsten oxide nanotubes, which in turn involves both the diffusion and adsorption of the gas during its reaction kinetics with the sensitive film itself. By utilizing the proposed multifrequency interrogation methodology, we demonstrate that the optimal temperature modulation frequencies employed for the nanotubes-based sensors to selectively detect hydrogen, carbon monoxide, ethanol, and dimethyl methyl phosphonate (DMMP) are significantly higher than those utilized for the nanodot-based sensors. This finding helps understand better the amelioration in selectivity that temperature modulation of metal oxides brings about, and, most importantly, it sets the grounds for the nanoengineering of gas-sensitive films to better exploit their practical usage. PMID:22834982

Vergara, Alexander; Calavia, Raul; Vázquez, Rosa María; Mozalev, Alexander; Abdelghani, Adnane; Huerta, Ramón; Hines, Evor H; Llobet, Eduard

2012-09-01

248

Improvement of long-term stability in SnO 2-based gas sensor for monitoring offensive odor  

Microsoft Academic Search

WO3\\/SnO2 ceramics has been suggested as an effective sensing material for monitoring offensive odor or pollutant gases. This work was focused on improving long-term stability, which has been a principal problem generally associated with SnO2 semiconductor gas sensors. Miniaturized thick film gas sensors were fabricated by screen-printing technique. Two types of sensor materials, W-doped SnO2 and WO3-mixed SnO2, were comparatively

Jong Hyun Park; Kwang Ho Kim

1999-01-01

249

?????????????????????????????????????????????????????????????????? ???????????????????????? TITANIUM DIOXIDE THIN FILMS PREPARED BY ION-ASSISTED E-BEAM EVAPORAION FOR GAS SENSING APPLICATIONS ?????? ???????????1, ???????? ?????????????2 ??? ?????? ??????????1  

Microsoft Academic Search

TiO2 is promising gas-sensing material due to its high temperature stability and catalytic properties. The physical and gas-sensing properties of the TiO2 gas sensor depend on the method and the condition of film preparation. In this work, we study the gas sensing behaviour of TiO2 thin film prepared by electron beam evaporation with ion-assisted deposition (IAD). TiO2 thin film has

C. Promjantuk; A. Wisitsoraat; P. Limsuwan

250

Zeolite thin film-coated long-period fiber grating sensors for detection of chemical vapors with high sensitivity  

NASA Astrophysics Data System (ADS)

In this study, a new zeolite thin film-coated long-period fiber grating (LPFG) sensor was developed and evaluated for chemical vapor detection. The sensor was fabricated by growing nanoporous MFI-type zeolite (pore size ~0.55nm) thin film on fiber grating using in situ hydrothermal crystallization method. The hydrothermal synthesis process was controlled by continuously monitoring the LPFG transmission spectrum evolution, which indicated the zeolite film formation and growth process. The zeolite-LPFG sensor was activated by calcination in air to remove the structural directing agent from the zeolite pores and then demonstrated for sensitive detection of chemical vapor in gas phases.

Zhang, Jian; Wei, Tao; Xiao, Hai; Dong, Junhang

2007-10-01

251

Gas mixing apparatus for automated gas sensor characterization  

NASA Astrophysics Data System (ADS)

We developed a computer-controlled gas mixing system that provides automated test procedures for the characterization of gas sensors. The focus is the generation of trace gases (e.g. VOCs like benzene or naphthalene) using permeation furnaces and pre-dilution of test gases. With these methods, the sensor reaction can be analyzed at very low gas concentrations in the ppb range (parts per billion) and even lower. The pre-dilution setup enables to cover a high concentration range (1:62?500) within one test procedure. Up to six test gases, humidity, oxygen content, total flow and their variation over time can be controlled via a LabVIEW-based user-interface.

Helwig, Nikolai; Schüler, Marco; Bur, Christian; Schütze, Andreas; Sauerwald, Tilman

2014-05-01

252

Diamond diode-based chemical gas sensors  

Microsoft Academic Search

The successful utilization of microelectronic-based gas sensors (MOS Capacitor, MOSFET, MS, and MIS diodes) in many practical applications such as automotive, aeronautical, commercial, and environmental has not been achieved due to the limited operating temperature range of Si and GaAs semiconductors (less than 200sp°C). Present development in the diamond technology provides an opportunity to address this problem. Along with its

Yasar Gurbuz

1997-01-01

253

Gas sensors based on carbon nanoflake/tin oxide composites for ammonia detection.  

PubMed

Carbon nanoflake (CNFL) was obtained from graphite pencil by using the electrochemical method and the CNFL/SnO2 composite material assessed its potential as an ammonia gas sensor. A thin film resistive gas sensor using the composite material was manufactured by the drop casting method, and the sensor was evaluated to test in various ammonia concentrations and operating temperatures. Physical and chemical characteristics of the composite material were assessed using SEM, TEM, SAED, EDS and Raman spectroscopy. The composite material having 10% of SnO2 showed 3 times higher sensor response and better repeatability than the gas sensor using pristine SnO2 nano-particle at the optimal temperature of 350°C. PMID:24473403

Lee, Soo-Keun; Chang, Daeic; Kim, Sang Wook

2014-03-15

254

A logarithmic multi-parameter model using gas sensor main and cross sensitivities to estimate gas concentrations in a gas mixture for SnO 2 gas sensors  

Microsoft Academic Search

In a metal-oxide semiconductor gas sensor, the sensitivity of the metal-oxide resistance to concentrations of reducing gases in the surrounding atmosphere is known to be related to adsorption and desorption of gas on the redox reactions between the gas and oxygen. Changes in the electric conductance due to these reactions were measured for tin dioxide semiconductor gas sensors. In this

A. Chaiyboun; R. Traute; T. Haas; O. Kiesewetter; T. Doll

2007-01-01

255

Use of different sensing materials and deposition techniques for thin-film sensors to increase sensitivity and selectivity  

Microsoft Academic Search

The performances of metal oxide semiconducting materials used as gas-sensing detectors depend strongly on their structural and morphological properties. The average grain size has been proved to play a prominent role and better sensor performances were found in polycrystalline films where the grain size is few tens of nm or smaller. On the other hand, thermal treatments during thin-film deposition

Sergio Nicoletti; Stefano Zampolli; Ivan Elmi; Leonello Dori; Maurizio Severi

2003-01-01

256

Review on optical fiber sensors with sensitive thin films  

NASA Astrophysics Data System (ADS)

The combination of fiber optics with nano-structure technologies and sensitive thin films offers great potential for the realization of novel sensor concepts. Miniatured optical fiber sensors with thin films as sensitive elements could open new fields for optical fiber sensor applications. Thin films work as sensitive elements and transducer to get response and feedback from environments, in which optical fibers are employed to work as signal carrier. This article presents some research work conducted at the National Engineering Laboratory for Optical Fiber Sensing Technologies in recent years. Concrete examples are: Pd/WO3 co-sputtered coating as sensing material for optical hydrogen sensors shows robust mechanical stability and meanwhile good sensing performance; TbDyFe magnetostrictive coating directly deposited on fiber Bragg grating (FBG) demonstrates its possibility of miniature optical magnetic field/current sensors, and 40-pm shift of the FBG wavelength happens at a magnetic field order of 50 mT.

Yang, Minghong; Dai, Jixiang

2012-03-01

257

In 2 O 3 Thin Films Obtained Through a Chemical Complexation Based Sol-Gel Process and Their Application as Gas Sensor Devices  

Microsoft Academic Search

A new approach is presented for preparing In2O3 thin films starting from inorganic precursors, based on a very simple but effective modification of the usual precipitation-peptization process. Indium nitrate was dissolved in methanol and In3+ ions were chelated with acetylacetone before adding concentrated base to the resulting solution. Such a route allowed obtaining long-term stable sols, from which films could

M. Epifani; S. Capone; R. Rella; P. Siciliano; L. Vasanelli; G. Faglia; P. Nelli; G. Sberveglieri

2003-01-01

258

Studies on Spray Deposited SnO2, Pd:SnO2 and F:SnO2 Thin Films for Gas Sensor Applications  

Microsoft Academic Search

Undoped tin oxide (TO), palladium?doped tin oxide (PTO) and fluorine?doped tin oxide (FTO) thin films have been prepared by spray pyrolysis method, under optimized conditions. Transmission measurement of the TO, PTO and FTO films have been studied in the UV?Visible region. Band gap energy evaluated from the spectral data lies between 3.15 eV and 3.8 eV. The X?ray diffraction analysis

N. Sankara Subramanian; B. Santhi; S. Sundareswaran; K. S. Venkatakrishnan

2006-01-01

259

Gas Sensors Based on Ceramic p-n Heterocontacts  

SciTech Connect

Ceramic p-n heterocontacts based on CuO/ZnO were successfully synthesized and a systematic study of their hydrogen sensitivity was conducted. The sensitivity and response rates of CuO/ZnO sensors were studied utilizing current-voltage, current-time, and impedance spectroscopy measurements. The heterocontacts showed well-defined rectifying characteristics and were observed to detect hydrogen via both dc and ac measurements. Surface coverage data were derived from current-time measurements which were then fit to a two-site Langmuir adsorption model quite satisfactorily. The fit suggested that there should be two energetically different adsorption sites in the system. The heterocontacts were doped in an attempt to increase the sensitivity and the response rate of the sensor. First, the effects of doping the p-type (CuO) on the sensor characteristics were investigated. Doping the p-type CuO with both acceptor and isovalent dopants greatly improved the hydrogen sensitivity. The sensitivity of pure heterocontact observed via I-V measurements was increased from {approx}2.3 to {approx}9.4 with Ni doping. Dopants also enhanced the rectifying characteristics of the heterocontacts. Small amounts of Li addition were shown to decrease the reverse bias (saturation) current to 0.2 mA at a bias level of -5V. No unambiguous trends were observed between the sensitivity, the conductivity, and the density of the samples. Comparing the two phase microstructure to the single phase microstructure there was no dramatic increase in the sensitivity. Kinetic studies also confirmed the improved sensor characteristics with doping. The dopants decreased the response time of the sensor by decreasing the response time of one of the adsorption sites. The n-type ZnO was doped with both acceptor and donor dopants. Li doping resulted in the degradation of the p-n junction and the response time of the sensor. However, the current-voltage behavior of Ga-doped heterocontacts showed the best rectifying characteristics with very high forward currents. Ga doped heterocontacts showed the highest sensitivity observed during current-time measurements as well, even though the sensor response was rather slow. Finally, a possible synergistic effect of doping both p and n-sides was studied by utilizing current-time measurements for 1.5 mol% Ni-CuO/1.5 mol% Ga-ZnO heterocontact. A sensitivity value of {approx}5.1 was obtained with the fastest response among all the samples. The time needed to reach 90% coverage was lowered by a factor of 4 when compared to the pure heterocontact and the time needed to reach 70% coverage was just over one minute. Heterocontact gas sensors are promising candidates for high temperature sensor applications. Today, Si-based microelectromechanical system (MEMS) technology has shown great promise for developing novel devices such as pressure sensors, chemical sensors, and temperature sensors through complex designs. However, the harsh thermal, vibrational, and corrosive environments common to many aerospace applications impose severe limitations on their use. Sensors based on ceramic p-n heterocontacts are promising alternatives because of their inherent corrosion resistance and environmental stability. The other advantages include their inherent tuning ability to differentiate between different reducing gases and a possible cost efficient production of a wireless sensor. Being a capacitive type sensor, its output can be transformed into a passive wireless device by creating a tuned LC circuit. In this way, the sensor output (the capacitance) can be accessed remotely by measuring the resonant frequency. The relatively simple structure of heterocontacts makes it suitable for thick film fabrication techniques to make sensor packages.

Seymen Murat Aygun

2004-12-19

260

A novel thick-film ceramic humidity sensor  

Microsoft Academic Search

The paper describes the results of studies on the fabrication and characterisation of a thick-film humidity sensor based on the semiconducting metal oxide MnWO4. The sensor element possesses a novel ‘sandwich’-configuration with a 40 ?m porous MnWO4 ceramic layer sandwiched by two 10 ?m polarity-reversed, interdigitated metal films. Instead of traditional glass frits, LiCl powders are used as adhesion promoters

Wenmin Qu; Jörg-Uwe Meyer

1997-01-01

261

Optical fiber gas sensor based on self-assembled gratings  

Microsoft Academic Search

The electrostatic self-assembled monolayer synthesis process is used to fabricate gas sensors by building up grating sensor elements on the ends of multimode optical fibers. These novel sensors can be designed to operate in the transmission windows of standard optical fibers and implemented using specific reference wavelengths to normalize the output signals. Experimental results for such sensors designed to detect

Francisco J. Arregui; Richard O. Claus; Kristie L. Cooper; Carlos Fernández-Valdivielso; Ignacio R. Matías

2001-01-01

262

Gas Main Sensor and Communications Network System  

SciTech Connect

Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the Northeast Gas Association (NGA), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. This projected was completed in April 2006, and culminated in the installation of more than 2 dozen GasNet nodes in both low- and high-pressure cast-iron and steel mains owned by multiple utilities in the northeastern US. Utilities are currently logging data (off-line) and monitoring data in real time from single and multiple networked sensors over cellular networks and collecting data using wireless bluetooth PDA systems. The system was designed to be modular, using in-pipe sensor-wands capable of measuring, flow, pressure, temperature, water-content and vibration. Internal antennae allowed for the use of the pipe-internals as a waveguide for setting up a sensor network to collect data from multiple nodes simultaneously. Sensor nodes were designed to be installed with low- and no-blow techniques and tools. Using a multi-drop bus technique with a custom protocol, all electronics were designed to be buriable and allow for on-board data-collection (SD-card), wireless relaying and cellular network forwarding. Installation options afforded by the design included direct-burial and external polemounted variants. Power was provided by one or more batteries, direct AC-power (Class I Div.2) and solar-array. The utilities are currently in a data-collection phase and intend to use the collected (and processed) data to make capital improvement decisions, compare it to Stoner model predictions and evaluate the use of such a system for future expansion, technology-improvement and commercialization starting later in 2006.

Hagen Schempf

2006-05-31

263

Ammonia sensors based on sensitive polyaniline films  

Microsoft Academic Search

We propose a new type of ammonia sensor with polyaniline (electroconducting polymer) as the sensitive element. Such sensors are characterized by high sensitivity, wide range of measured concentrations (1–2000 ppm) and high stability of electrical parameters. The use of polyaniline ensures high chemical stability of the sensors in oxidizing ambients. A sensor design based on a silicon chip custom-packed into

A. L. Kukla; Yu. M. Shirshov; S. A. Piletsky

1996-01-01

264

Nanoparticle cluster gas sensor: controlled clustering of SnO? nanoparticles for highly sensitive toluene detection.  

PubMed

Gas sensing with nanosized oxide materials is attracting much attention because of its promising capability of detecting various toxic gases at very low concentrations. In this study, using clustered SnO2 nanoparticles formed by controlled particle aggregation, we fabricated highly sensitive gas sensing films to detect large gas molecules such as toluene. A hydrothermal method using stanic acid (SnO2·nH2O) gel as a precursor produced monodispersed SnO2 nanoparticles of ca. 5 nm at pH 10.6. Decreasing the solution pH to 9.3 formed SnO2 clusters of ca. 45 nm that were assemblies of the monodispersed nanoparticles, as determined by dynamic light scattering, X-ray diffraction, and transmission electron microscopy analyses. Porous gas sensing films were successfully fabricated by a spin-coating method using the clustered nanoparticles due to the loose packing of the larger aggregated particles. The sensor devices using the porous films showed improved sensor responses (sensitivities) to H2 and CO at 300 °C. The enhanced sensitivity resulted from an increase in the film's porosity, which promoted the gas diffusivity of the sensing films. Pd loading onto the clustered nanoparticles further upgraded the sensor response due to catalytic and electrical sensitization effects of Pd. In particular, the Pd-loaded SnO2 nanoparticle clusters showed excellent sensitivity to toluene, able to detect it at down to low ppb levels. PMID:24635838

Suematsu, Koichi; Shin, Yuka; Hua, Zhongqiu; Yoshida, Kohei; Yuasa, Masayoshi; Kida, Tetsuya; Shimanoe, Kengo

2014-04-01

265

Thin Film on CMOS Active Pixel Sensor for Space Applications  

PubMed Central

A 664 × 664 element Active Pixel image Sensor (APS) with integrated analog signal processing, full frame synchronous shutter and random access for applications in star sensors is presented and discussed. A thick vertical diode array in Thin Film on CMOS (TFC) technology is explored to achieve radiation hardness and maximum fill factor.

Schulze Spuentrup, Jan Dirk; Burghartz, Joachim N.; Graf, Heinz-Gerd; Harendt, Christine; Hutter, Franz; Nicke, Markus; Schmidt, Uwe; Schubert, Markus; Sterzel, Juergen

2008-01-01

266

Influence of Cu overlayer on the properties of SnO 2-based gas sensors  

Microsoft Academic Search

The series of gas sensors based on SnO2 thin films and doped with different amount of Cu was prepared by using dc magnetron sputtering. The surface properties and chemical composition of the sensors covered with Cu and Pt overlayers were studied by XPS, SIMS and optical UV–VIS spectroscopy. The electrical conductivity controlled by surface interaction with gases (CO, H2, Cl2)

F. Cirilli; S Ka?iulis; G Mattogno; A Galdikas; A Mironas; A Šetkus

1998-01-01

267

Compact portable QEPAS multi-gas sensor  

NASA Astrophysics Data System (ADS)

A quartz-enhanced photoacoustic spectroscopy (QEPAS) based multi-gas sensor was developed to quantify concentrations of carbon monoxide (CO), hydrogen cyanide (HCN), hydrogen chloride (HCl), and carbon dioxide (CO2) in ambient air. The sensor consists of a compact package of dimensions 25cm x 25cm x 10cm and was designed to operate at atmospheric pressure. The HCN, CO2, and HCl measurement channels are based on cw, C-band telecommunication-style packaged, fiber-coupled diode lasers, while the CO channel uses a TO can-packaged Sb diode laser as an excitation source. Moreover, the sensor incorporates rechargeable batteries and can operate on batteries for at least 8 hours. It can also operate autonomously or interact with another device (such as a computer) via a RS232 serial port. Trace gas detection limits of 7.74ppm at 4288.29cm-1 for CO, 450ppb at 6539.11 cm-1 for HCN, 1.48ppm at 5739.26 cm-1 for HCl and 97ppm at 6361.25 cm-1 for CO2 for a 1sec average time, were demonstrated.

Dong, Lei; Kosterev, Anatoliy A.; Thomazy, David; Tittel, Frank K.

2011-01-01

268

Engineered nanostructured thin films for enhanced surface acoustic wave sensors  

NASA Astrophysics Data System (ADS)

Sensor technologies profoundly impact all aspects of our everyday lives. Advances have led to smaller devices, faster response times, reduced costs, higher specificity and sensitivity, and even new sensing technologies. Surface acoustic wave (SAW) technology, which has been around for many decades already, is an example of a newer sensing technology that has begun to be studied for sensing applications. Many advantages of SAW sensors have been identified, in particular the high sensitivity, low cost and wireless capability. However, as the technology is still in its infancy for sensing applications, many improvements and refinements on the platform have yet to be explored. With the arrival of nanotechnology, many existing technologies have benefited from integrating with the new findings that nanotechnology has brought forth. This thesis investigates the enhancement of existing SAW sensors using nanostructured films fabricated by a thin film deposition process known as glancing angle deposition (GLAD). The GLAD technique is a highly flexible and precise thin film fabrication method that is able to create high-surface-area thin films. This high-surface-area characteristic of these films is the driving motivation in their utilization to enhance the performance of SAW sensors. This thesis first demonstrates that dense, extremely high surface area films can be deposited on SAW sensors without adversely affecting device performance. These modified sensors were then studied as humidity sensors to demonstrate improved sensitivity with the addition of the GLAD films. Before the sensors with GLAD films could be tested in a liquid environment, ion-milling was investigated as a method of eliminating the clustering of the individual structures typically seen after exposure to liquids. These modified films were extended for use on the SAW sensors to investigate liquid sensing performance. The performance of SAW devices with clustered films was also studied for comparison. Both types of films were shown to increase sensitivity greatly over the reference SAW device. The success of these results validates the ability of GLAD films to enhance the sensitivity of not only SAW devices, but potentially other sensing technologies as well.

Kwan, Jonathan Kwok Wah

269

Electrochemical high-temperature gas sensors  

NASA Astrophysics Data System (ADS)

Combustion produced common air pollutant, NOx associates with greenhouse effects. Its high temperature detection is essential for protection of nature. Component-integration capable high-temperature sensors enable the control of combustion products. The requirements are quantitative detection of total NOx and high selectivity at temperatures above 500°C. This study reports various approaches to detect NO and NO2 selectively under lean and humid conditions at temperatures from 300°C to 800°C. All tested electrochemical sensors were fabricated in planar design to enable componentintegration. We suggest first an impedance-metric gas sensor for total NOx-detection consisting of NiO- or NiCr2O4-SE and PYSZ-electrolyte. The electrolyte-layer is about 200?m thickness and constructed of quasi-single crystalline columns. The sensing-electrode (SE) is magnetron sputtered thin-layers of NiO or NiCr2O4. Sensor sensitivity for detection of total NOx has been measured by applying impedance analysis. The cross-sensitivity to other emission gases such as CO, CO2, CH4 and oxygen (5 vol.%) has been determined under 0-1000ppm NO. Sensor maintains its high sensitivity at temperatures up to 550°C and 600°C, depending on the sensing-electrode. NiO-SE yields better selectivity to NO in the presence of oxygen and have shorter response times comparing to NiCr2O4-SE. For higher temperature NO2-sensing capability, a resistive DC-sensor having Al-doped TiO2-sensing layers has been employed. Sensor-sensitivity towards NO2 and cross-sensitivity to CO has been determined in the presence of H2O at temperatures 600°C and 800°C. NO2 concentrations varying from 25 to 100ppm and CO concentrations from 25 to 75ppm can be detected. By nano-tubular structuring of TiO2, NO2 sensitivity of the sensor was increased.

Saruhan, B.; Stranzenbach, M.; Yüce, A.; Gönüllü, Y.

2012-05-01

270

Dielectric Coating For Hot-Film Flow Sensors  

NASA Technical Reports Server (NTRS)

Very-thin-film dielectric coating stable over range of temperatures developed. This dielectric coating, combination of fused silica and thermoplastic polymer, has sufficient stability to withstand stresses placed upon it by cycling to and from cryogenic temperatures. Coating tailored to meet almost any criterion of roughness height. Useful for research in application of hot-film sensors to airfoils.

Hopson, Purnell, Jr.; Tran, Sang Q.

1990-01-01

271

Method of Forming Micro-Sensor Thin-Film Anemometer  

NASA Technical Reports Server (NTRS)

A device for measuring turbulence in high-speed flows is provided which includes a micro- sensor thin-film probe. The probe is formed from a single crystal of aluminum oxide having a 14 deg half-wedge shaped portion. The tip of the half-wedge is rounded and has a thin-film sensor attached along the stagnation line. The bottom surface of the half-wedge is tilted upward to relieve shock induced disturbances created by the curved tip of the half-wedge. The sensor is applied using a microphotolithography technique.

Sheplak, Mark (Inventor); McGinley, Catherine B. (Inventor); Spina, Eric F. (Inventor); Stephens, Ralph M. (Inventor); Hopson, Purnell, Jr. (Inventor); Cruz, Vincent B. (Inventor)

2000-01-01

272

Temperature and Humidity Dependence of a Polymer-Based Gas Sensor  

NASA Technical Reports Server (NTRS)

This paper quantifies the temperature and humidity dependence of a polymer-based gas sensor. The measurement and analysis of three polymers indicates that resistance changes in the polymer films, due to temperature and humidity, can be positive or negative. The temperature sensitivity ranged from +1600 to -320 ppm/nd the relative sensitivity ranged from +1100 to -260 ppm/%.

Ryan, M. A.; Buehler, M. G.

1997-01-01

273

Optical and Nonlinear Optical Response of Light Sensor Thin Films  

Microsoft Academic Search

For potential ultrafast optical sensor application, both VO2 thin films and nanocomposite crystal-Si enriched SiO2 thin films grown on fused quartz substrates were successfully prepared using pulsed laser deposition (PLD) and RF co-sputtering techniques. In photoluminescence (PL) measurement c-Si\\/SiO2 film contains nanoparticles of crystal Si exhibits strong red emission with the band maximum ranging from 580 to 750 nm. With

Huimin Liu; Armando Rua; Omar Vasquez; Valentin S. Vikhnin; Felix E. Fernandez; Luis F. Fonseca; Oscar Resto; Svi Z. Weisz

2005-01-01

274

Study for Electrode Metals on Taste Sensor with LB film  

NASA Astrophysics Data System (ADS)

In this paper, sensor responses with only metal electrode as Au, Cr, Ti and more with LB film were described. LB film material was the Dioctadecyldimethylammonium bromide combined by PVSK as an underlayer. To detect five basic taste substances, sensor parameters were defined as maximum voltage change and response time. Response time for sourness and umami with Ti and Cr evaporated metal electrode was larger than that of usual Au electrode. LB film effect was finally found to increase response time for five basic taste materials.

Yokoya, Takahiro; Hirata, Takamichi; Akiya, Masahiro

275

Development of a New Respirator for Organic Vapors with a Breakthrough Detector Using a Semiconductor Gas Sensor  

Microsoft Academic Search

A method for determining breakthrough of organic vapors in a respirator cartridge was developed. A thick film semiconductor gas sensor was used as a breakthrough detector. Air containing organic vapor was introduced into the cartridge, and an output signal from the sensor inserted in the downstream flow of the cartridge was recorded on an IC card. Simultaneously, the breakthrough curve

Hajime Hori; Toru Ishidao; Sumiyo Ishimatsu

2003-01-01

276

Enhancement of gas sensor response of nanocrystalline zinc oxide for ammonia by plasma treatment  

NASA Astrophysics Data System (ADS)

The effect of oxygen plasma treatment on nanocrystalline ZnO thin film based gas sensor was investigated. ZnO thin films were synthesized on alkali-free glass substrates by a sol-gel process. ZnO thin films were treated with oxygen plasma to change the number of vacancies/defects in ZnO. The effect of oxygen plasma on the structural, electrical, optical and gas sensing properties was investigated as a function of plasma treatment time. The results suggest that the microstructure and the surface morphology can be tuned by oxygen plasma treatment. The optical transmission in the visible range varies after the oxygen plasma treatment. Moreover, it is found that the oxygen plasma has significant impact on the electrical properties of ZnO thin films indicating a variation of resistivity. The oxygen plasma treated ZnO thin film exhibits an enhanced sensing response towards NH3 in comparison with that of the as-deposited ZnO sensor. When compared with the as-deposited ZnO film, the sensing response was improved by 50% for the optimum oxygen plasma treatment time of 8 min. The selectivity of 8 min plasma treated ZnO sensor was also examined for an important industrial gas mixture of H2, CH4 and NH3.

Hou, Yue; Jayatissa, Ahalapitiya H.

2014-08-01

277

Humidity sensors based on polymer thin films  

Microsoft Academic Search

Studies on humidity sensors fabricated with organic polymers for the last 10 years are reviewed. Several useful methods for improving the characteristics of humidity sensors based on polymers are proposed. In the case of a resistive-type sensor, cross-linking of hydrophilic polymers or formation of interpenetrated polymer networks with a hydrophobic polymer makes the hydrophilic polymers durable at high humidities. Graft

Y Sakai; Y Sadaoka; M Matsuguchi

1996-01-01

278

Carbon dioxide gas sensor using a graphene sheet  

Microsoft Academic Search

In this article, we report on a high-performance graphene carbon dioxide (CO2) gas sensor fabricated by mechanical cleavage. Unlike other solid-state gas sensors, the graphene sensor can be operated under ambient conditions and at room temperature. Changes in the device conductance are measured for various concentrations of CO2 gas adsorbed on the surface of graphene. The conductance of the graphene

Hyeun Joong Yoon; Do Han Jun; Jin Ho Yang; Zhixian Zhou; Sang Sik Yang; Mark Ming-Cheng Cheng

2011-01-01

279

Fast and robust gas identification system using an integrated gas sensor technology and Gaussian mixture models  

Microsoft Academic Search

Among the most serious limitations facing the success of future consumer gas identification systems are the drift problem and the real-time detection due to the slow response of most of today's gas sensors. This paper shows that the combination of an integrated sensor array and a Gaussian mixture model permits success in gas identification problems. An integrated sensor array has

Sofiane Brahim-Belhouari; Amine Bermak; Minghua Shi; Philip C. H. Chan

2005-01-01

280

Experimental study on optical fiber bundle hydrogen sensor based on palladium-silver optical thin film  

NASA Astrophysics Data System (ADS)

In this paper, a 20 nm palladium-silver (Pd/Ag) ultrathin optical film is used for hydrogen gas sensing. The mole ratio of the two metals is controlled at Pd:Ag=3:1. In the direct current (DC) sputtering machine, the optical thin film is evaporated on the optical glass. Compared with pure palladium, the Pd/Ag alloy can increase the life and the stability of the sensing film. Optimum sputtering parameters for Pd/Ag alloy are presented in this paper, and the effects of different experimental conditions for hydrogen sensor are investigated, including the temperature effect, humidity effect and cross sensitivity of hydrogen sensor for different gases. The experiment results indicate that the hydrogen sensor based on Pd/Ag optical thin film exhibits good sensing characteristics. The existing of CO and water in hydrogen increases the response time and decreases the response amplitude of optical fiber bundle hydrogen sensor. The experiment results show that the increasing temperature can eliminate the effect and shorten hydrogen sensor response time effectively.

Cui, Lu-jun; Shang, Hui-chao; Zhang, Gang; Li, Yong; Zhao, Ze-xiang

2013-01-01

281

Carbon-Nanotube-Based Chemical Gas Sensor  

NASA Technical Reports Server (NTRS)

Conventional thermal conductivity gauges (e.g. Pirani gauges) lend themselves to applications such as leak detectors, or in gas chromatographs for identifying various gas species. However, these conventional gauges are physically large, operate at high power, and have a slow response time. A single-walled carbon-nanotube (SWNT)-based chemical sensing gauge relies on differences in thermal conductance of the respective gases surrounding the CNT as it is voltage-biased, as a means for chemical identification. Such a sensor provides benefits of significantly reduced size and compactness, fast response time, low-power operation, and inexpensive manufacturing since it can be batch-fabricated using Si integrated-circuit (IC) process technology.

Kaul, Arunpama B.

2010-01-01

282

Film bulk acoustic-wave resonator based ultraviolet sensor  

NASA Astrophysics Data System (ADS)

This letter described ultraviolet (UV) radiation sensing with ZnO based film bulk acoustic-wave resonator (FBAR). The resonant frequency upshifted when there was UV illumination on the FBAR. For 365 nm UV light, the frequency upshift was 9.8 kHz with an intensity of 600 ?W/cm2, and the detection limit of the sensor was 6.5 nW. The frequency increase in the FBAR UV sensor was proposed to be due to the density decrease in ZnO film upon UV illumination. When UV was incident on the ZnO film, it can cause oxygen desorption from the ZnO surface, resulting in density decrease in the film. This study has proven the feasibility of detection of low intensity UV using ZnO film based FBAR.

Qiu, X.; Zhu, J.; Oiler, J.; Yu, C.; Wang, Z.; Yu, H.

2009-04-01

283

Mesoporous silica thin films for alcohol sensors  

Microsoft Academic Search

Silica mesoporous films using cetyltrimethylammonium bromide surfactant as a template have been prepared. The films have been deposited on silicon and alumina substrates by dip-coating and calcined at 250 and 450°C. The films were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy and Rutherford backscattering spectrometry. The films have been shown to maintain the mesophase after calcination, at 250°C

Plinio Innocenzi; Alessandro Martucci; Massimo Guglielmi; Andrea Bearzotti; Enrico Traversa; Jean Claude Pivin

2001-01-01

284

Compact and multiplexible hydrogen gas sensor assisted by self-referencing technique.  

PubMed

We have experimentally implemented a multiplexible but compact fiber sensor system suitable for multipoint sensing of hydrogen gas leakage. By making dual cavities along an optical fiber and coating a palladium film only at the end of the fiber tip, the measurement errors induced by the optical source power fluctuation and the mechanical perturbation in the lead fiber could be compensated. By adjusting the length of the dual-cavity, the capability of multiplexing several hydrogen sensors could be achieved. The experiment results showed that the response speed of the sensor was increasing with temperature, but at a low temperature the response amplitude became large. PMID:21935185

Park, Kwan Seob; Kim, Young Ho; Eom, Joo Beom; Park, Seong Jun; Park, Min-Su; Jang, Jae-Hyeong; Lee, Byeong Ha

2011-09-12

285

Thin Film Ceramic Strain Sensor Development for High Temperature Environments  

NASA Technical Reports Server (NTRS)

The need for sensors to operate in harsh environments is illustrated by the need for measurements in the turbine engine hot section. The degradation and damage that develops over time in hot section components can lead to catastrophic failure. At present, the degradation processes that occur in the harsh hot section environment are poorly characterized, which hinders development of more durable components, and since it is so difficult to model turbine blade temperatures, strains, etc, actual measurements are needed. The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in harsh environments. The effort at the NASA Glenn Research Center (GRC) to develop high temperature thin film ceramic static strain gauges for application in turbine engines is described, first in the fan and compressor modules, and then in the hot section. The near-term goal of this research effort was to identify candidate thin film ceramic sensor materials and provide a list of possible thin film ceramic sensor materials and corresponding properties to test for viability. A thorough literature search was conducted for ceramics that have the potential for application as high temperature thin film strain gauges chemically and physically compatible with the NASA GRCs microfabrication procedures and substrate materials. Test results are given for tantalum, titanium and zirconium-based nitride and oxynitride ceramic films.

Wrbanek, John D.; Fralick, Gustave C.; Gonzalez, Jose M.; Laster, Kimala L.

2008-01-01

286

Development of MWCNTs/alumina composite-based sensor for trace level ammonia gas sensing  

NASA Astrophysics Data System (ADS)

Multi-walled carbon nanotube (MWCNT)/alumina (Al2O3) composite thin film-based low cost, rigid and highly efficient sensors were developed for trace level ammonia (NH3) gas sensing applications. Composite films were prepared by dispersing MWCNTs in varying concentration in alumina solution following the sol-gel process. The sensor response as a function MWCNT concentrations were measured and compared. The notable characteristics of these sensors are fast response time (10 minutes), and excellent reproducibility with detection level up to 6 ppm. Although poor NH3 desorption causes a high recovery time, fast and complete recovery was acquired using appropriate thermal treatment protocol. The sensitivity was found to be proportional to NH3 concentrations in the range 6-25 ppm and then gradually saturated at higher concentrations. However, a decrease in the sensor response was observed with increase in concentrations of MWCNTs.

Sharma, Sakshi; Hussain, Shahir; Sengupta, K.; Islam, S. S.

2013-06-01

287

SiC-Based Schottky Diode Gas Sensors.  

National Technical Information Service (NTIS)

Silicon carbide based Schottky diode gas sensors are being developed for high temperature applications such as emission measurements. Two different types of gas sensitive diodes will be discussed in this paper. By varying the structure of the diode, one c...

G. W. Hunter P. G. Neudeck L. Y. Chen D. Knight C. C. Liu Q. H. Wu

1997-01-01

288

A sensitivity enhanced gas sensor based on carbon nanotubes around microfiber  

NASA Astrophysics Data System (ADS)

In this paper, a carbon nanotubes (CNTs) films around microfiber gas sensor is reported. The CNTs films are deposited uniformly on the surface of microfiber with Langmuir-Blodgett(LB) coating technology. The CNTs which are rank tightly perform as cladding of microfiber and show the well absorption characteristic when they are used for gas sensing. The experimental results have shown the variations of intensity of transmitting light while the concentration of acetone and xylene around CNTs films based microfiber are different, The changes of light intensity are 3.1dB and 9.5dB respectively, when acetone and xylene concentrations reached 1200ppm. As the gas vaporizing freely, the results also show the fine characteristic with real-time response. The results demonstrate that this type of CNTs films around microfiber structure has great potential applied in trace gases detecting in micro-scale.

Jia, Lan; Wu, Yu; Yao, Baicheng; Yang, Feiya; Rao, Yunjiang

2012-01-01

289

A Polycrystalline Diamond Thin Film Based Hydrogen Sensor  

Microsoft Academic Search

A new microelectronic gas sensor utilizing polycrystallinediamondfilm in conjunction with a catalytic metal has been developed for hydrogen detection. The sensor is fabricated in a layered Pd\\/i-diamond\\/p-diamond metal-insulator-semiconductor (MIS) Schottky-diode configuration on a tungsten substrate. The performance of the sensor for H2 detection has been examined in the temperature range 27-300°C. The analysis of the steady-state reaction kinetics has confirmed

David V. Kerns; W P Kang; Y Gurbuz; J L Davidson

2002-01-01

290

Oxygen sensor for monitoring gas mixtures containing hydrocarbons  

DOEpatents

A gas sensor measures O.sub.2 content of a reformable monitored gas containing hydrocarbons H.sub.2 O and/or CO.sub.2, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system.

Ruka, Roswell J. (Pittsburgh, PA); Basel, Richard A. (Pittsburgh, PA)

1996-01-01

291

Oxygen sensor for monitoring gas mixtures containing hydrocarbons  

DOEpatents

A gas sensor measures O{sub 2} content of a reformable monitored gas containing hydrocarbons, H{sub 2}O and/or CO{sub 2}, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system. 4 figs.

Ruka, R.J.; Basel, R.A.

1996-03-12

292

Study of real-time visualization of gas\\/odor flow image using gas sensor array  

Microsoft Academic Search

A new method to find a gas\\/odor source is proposed. A portable homogeneous gas sensor array is used to visualize the flow of a target gas. The direction of a gas source is estimated using a real-time image processing algorithm, and the source is located by following the estimated direction. The design of the sensor array has been performed using

H Ishida; T Yamanaka; N Kushida; T Nakamoto; T Moriizumi

2000-01-01

293

Controlling a gas\\/odor plume-tracking robot based on transient responses of gas sensors  

Microsoft Academic Search

Gas sensors provide an artificial sense of smell for a mobile robot to track an airborne gas\\/odor plume and locate its source. However, a slow response of gas sensors has been the major factor limiting the development of plume-tracking robots. This paper describes a new control algorithm that breaks the limitation. The basic idea is to detect onsets of gas

Hiroshi Ishida; Gouki Nakayama; Takamichi Nakamoto; Toyosaka Moriizumi

2005-01-01

294

CMOS Interfacing for Integrated Gas Sensors: A Review  

Microsoft Academic Search

Modern gas sensor technology is becoming an important part of our lives. It has been applied within the home (monitoring CO levels from boilers), the workplace (e.g., checking levels of toxic gases) to healthcare (monitoring gases in hospitals). However, historically the high price of gas sensors has limited market penetration to niche applications, such as safety in mines or petrochemical

Julian W. Gardner; Prasanta K. Guha; Florin Udrea; James A. Covington

2010-01-01

295

Development of SiC Gas Sensor Systems  

Microsoft Academic Search

Silicon carbide (SiC) based gas sensors have significant potential to address the gas sensing needs of aerospace applications such as emission monitoring, fuel leak detection, and fire detection. However, in order to reach that potential, a range of technical challenges must be overcome. These challenges go beyond the development of the basic sensor itself and include the need for viable

G. W. Hunter; P. G. Neudeck; R. S. Okojie; G. M. Beheim; V. Thomas; L. Chen; D. Lukco; C. C. Liu; B. Ward; D. Makel

2002-01-01

296

Millisecond response time measurements of high temperature gas sensors  

Microsoft Academic Search

We present a new apparatus for measuring the response times of a gas sensor with millisecond resolution, while also capturing the slower components of the response such as the steady state value. Laser induced fluorescence (LIF) imaging was used to quantify the exchange rate of the sensor's ambient gas. The millisecond response of high temperature (up to 950 K) field

Peter Tobias; Hui Hu; Manooch Koochesfahani; Ruby N. Ghosh

2004-01-01

297

Flexible pentacene thin film transistors as DNA hybridization sensor  

Microsoft Academic Search

A DNA hybridization sensor using pentacene thin film transistors (TFTs) is an excellent candidate for disposable sensor applications due to their low-cost fabrication process and fast detection. We fabricated pentacene TFTs on flexible substrate for the sensing of DNA hybridization. The 100 mer ss-DNA (poly A\\/poly T) or 100 bp ds-DNA (poly A\\/poly T hybrid) are deposited from a solution

Jung-Min Kim; Sandeep Kumar Jha; Rohit Chand; Dong-Hoon Lee; Yong-Sang Kim

2011-01-01

298

Characterization of the polypyrrole film-piezoelectric sensor combination.  

PubMed

Polymerization of pyrrole onto the electrode surfaces of thickness-shear-mode acoustic wave sensors at various levels of oxidation has been performed with electrochemical methods. The resulting films of polypyrrole have been characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Frequency decreases for the polypyrrole-coated sensors exposed to methanol, toluene and ammonia have been evaluated in terms of the various interactions occurring at the polymer surface. PMID:18965400

Vigmond, S J; Kallury, K M; Ghaemmaghami, V; Thompson, M

1992-04-01

299

Biochemical sensors based on thin-film waveguide  

Microsoft Academic Search

Biochemical sensors based on thin-film waveguide are proposed which can measure the concentration of sample solutions. In order to investigate the applicability of these sensors to Ca2+ and glucose measurement, the waveguide was fabricated with 3 layers: the substrate (pyrex glass), the waveguide layer (sputtered with Corning 7059 glass) and sample layer having PVC sensing membrane and\\/or sample chamber. We

Haruyuki MINAMITANI; Kyungho KIM; Kunihiro MATSUMOTO

1998-01-01

300

Low-power gas sensors based on work-function measurement in low-cost hybrid flip–chip technology  

Microsoft Academic Search

To implement low-power gas sensors with low component costs, the principle of work-function read out via a hybrid suspended gate FET (SGFET) is being pursued, whereby a freely selectable sensor film undergoes a reversible work-function change corresponding to the build-up of a potential difference on the surface in response to gas adsorption\\/reaction. This is read out via an ISFET structure.

M. Fleischer; B. Ostrick; R. Pohle; E. Simon; H. Meixner; C. Bilger; F. Daeche

2001-01-01

301

Preparation and Analysis of Platinum Thin Films for High Temperature Sensor Applications.  

National Technical Information Service (NTIS)

A study has been made of platinum thin films for application as high temperature resistive sensors. To support NASA Glenn Research Center s high temperature thin film sensor effort, a magnetron sputtering system was installed recently in the GRC Microsyst...

J. D. Wrbanek K. L. H. Laster

2005-01-01

302

Humidity sensors based on aluminum phthalocyanine chloride thin films  

NASA Astrophysics Data System (ADS)

In present paper, the fabrication and humidity sensing properties of aluminum phthalocyanine chloride (AlPcCl) thin film based sensors have been presented. AlPcCl thin films with nominal thickness of 50-100 nm are deposited on glass substrates between pre-deposited 50 nm thick aluminum electrodes. The gap between the electrodes is 50 ?m. It is observed that the sensing mechanism is based on the variation of resistance with change in humidity. For change in relative humidity (RH) from 20% to 92%, the change in resistance is 22.2×102 and 13.3×102 times respectively for the sensors having 50 nm and 100 nm thick AlPcCl films, while the 1 h annealing of these samples at 100 °C results in increase in average sensitivity up to 30% and 40% respectively. The consequence of measuring frequency and absorption-desorption behavior of the humidity sensor are also discussed in detail. It is also observed that annealing results in minimization of hysteresis and reduction of recovery time (?rec) up to 63% and 70% in sensors with 50 nm and 100 nm thick organic film respectively, while the response (?res) time is 10 s for both the sensors.

Chani, Muhammad Tariq Saeed; Karimov, Kh. S.; Ahmad Khalid, F.; Raza, Kabeer; Umer Farooq, Muhammad; Zafar, Qayyum

2012-08-01

303

Thin film planar waveguide sensor for liquid phase absorbance measurements  

SciTech Connect

A thin film planar waveguide is studied for application as a chemical sensor for liquid-phase absorbance measurements. The waveguide is comprised of a thin film of tantalum pentoxide deposited on a glass substrate with a pair of diffraction gratings etched into the substrate surface. The buried grating couplers allow the launch and collection optics to be isolated from the liquid sample. The response to an absorbing dye and different refractive index (RI) solutions is studied and compared to theoretical predictions. The sensor has an absorbance sensitivity equivalent to a 1 mm path length in a conventional transmission measurement. A method to reduce the intensity changes due to solution RI is demonstrated.

DeGrandpre, M.D.; Burgess, L.W. (Univ. of Washington, Seattle (USA)); White, P.L.; Goldman, D.S. (Battelle Pacific Northwest Laboratory, Richland, WA (USA))

1990-09-15

304

Organic material as gas sensor for farm application  

Microsoft Academic Search

Polyaniline is a organic material with potential use in electronic nose sensors and has been shown to be highly sensitive to ammonia. This paper shows results of the characterization of ultra thin films of Polyaniline for applications as gaseous ammonia sensor at NH3 monitoring at chicken farms. A sensitive layer based on such material deposited on the top of interdigital

M. P. Regaco; E. A. T. Dirani; F. J. Fonseca; A. M. de Andrade

2005-01-01

305

Hydrogen gas sensing properties of PdO thin films with nano-sized cracks  

NASA Astrophysics Data System (ADS)

We report on a novel method for the fabrication of highly sensitive hydrogen gas sensors based on palladium oxide thin films and have investigated their hydrogen sensing properties and nanostructures. To our knowledge, this is the first report on the use of palladium oxide and reduced palladium thin films as hydrogen sensors. The palladium oxide thin films were deposited on thermally oxidized Si substrates using a reactive direct current (DC) magnetron sputtering system. Considerable changes in the resistance of the palladium oxide thin films were observed when they were initially exposed to hydrogen gas, as a result of the reduction process. After the initial exposure to hydrogen gas of PdO30%, its sensitivity increased up to ~ 4.5 × 103%. The morphology of the PdO surface was analyzed using a scanning electron microscope (SEM), in order to investigate the interactions between palladium oxide and hydrogen. The SEM images showed a large number of nano-sized cracks on the surface of the palladium oxide during the reduction process, which acted to increase the effective surface-to-volume ratio. The response behaviors of the reduced Pd films to hydrogen gas were reversible and had an enhanced sensing property when compared with those of the pure Pd films. In addition, their sensitivities and response times were improved due to the nano-sized cracks on the surfaces. The results demonstrate that palladium oxide and reduced palladium thin films can be applied for use in highly sensitive hydrogen sensors.

Tack Lee, Young; Lee, Jun Min; Kim, Yeon Ju; Hyoun Joe, Jin; Lee, Wooyoung

2010-04-01

306

Pd–Pt alloy as a catalyst in gasochromic thin films for hydrogen sensors  

Microsoft Academic Search

We have used Pd–Pt alloy as the catalyst in the hydrogen sensor thin film. Palladium and platinum were co-sputtered on top of a tungsten oxide layer grown by reactive sputtering. Both the sensitivity and the durability were dramatically improved over the case of a palladium single-component catalyst. The fractional change in the optical absorption on exposure to 1% hydrogen gas

Jae Young Shim; Jae Dong Lee; Jung Mo Jin; Hyeonsik Cheong; Se-Hee Lee

2009-01-01

307

Pd Nanoparticles and Thin Films for Room Temperature Hydrogen Sensor  

PubMed Central

We report the application of palladium nanoparticles and thin films for hydrogen sensor. Electrochemically grown palladium particles with spherical shapes deposited on Si substrate and sputter deposited Pd thin films were used to detect hydrogen at room temperature. Grain size dependence of H2sensing behavior has been discussed for both types of Pd films. The electrochemically grown Pd nanoparticles were observed to show better hydrogen sensing response than the sputtered palladium thin films. The demonstration of size dependent room temperature H2sensing paves the ways to fabricate the room temperature metallic and metal–metal oxide semiconductor sensor by tuning the size of metal catalyst in mixed systems. H2sensing by the Pd nanostructures is attributed to the chemical and electronic sensitization mechanisms.

2009-01-01

308

Development of a PVDF film sensor for infrastructure monitoring  

NASA Astrophysics Data System (ADS)

Development of a health monitoring system is of vital importance for all civil infrastructures. However, this effort has been stymied in part by the lack of suitable low priced sensors and associated signal conditioning. Very often the requirement of a controlled stable power supply to the sensor itself poses another challenge. Piezoelectric polymer films offer an excellent alternative to the ubiquitous strain gage technology. The PVDF film generates an electrical charge when mechanically deformed. The PVDF film is typically a high impedance source with a capacitance in the nanofarad range and measurement of low frequency event can pose a challenge. The authors have utilized a charge mode amplification scheme for measuring quasi-static processes. The processed signal can be transmitted to a data acquisition system via a RF microelectronic circuit. The PVDF film as a transducer can be cut to very small size and are very affordable at around 50 cents per sensor. The whole circuitry can be integrated into one single unit. It would require very low power to function and could be embedded in the structure for a large number of remote applications. In this article the authors have reported the result of the various characterization test that have been carried out to determine the suitability of the basic film as the core of an autoadaptive sensor system to be designed for infrastructure monitoring.

Satpathi, Debashis; Victor, J. P.; Wang, Ming L.; Yang, H. Y.; Shih, C. C.

1999-05-01

309

Magnetoelastic sensor for characterizing properties of thin-film/coatings  

NASA Technical Reports Server (NTRS)

An apparatus for determining elasticity characteristics of a thin-film layer. The apparatus comprises a sensor element having a base magnetostrictive element at least one surface of which is at least partially coated with the thin-film layer. The thin-film layer may be of a variety of materials (having a synthetic and/or bio-component) in a state or form capable of being deposited, manually or otherwise, on the base element surface, such as by way of eye-dropper, melting, dripping, brushing, sputtering, spraying, etching, evaporation, dip-coating, laminating, etc. Among suitable thin-film layers for the sensor element of the invention are fluent bio-substances, thin-film deposits used in manufacturing processes, polymeric coatings, paint, an adhesive, and so on. A receiver, preferably remotely located, is used to measure a plurality of values for magneto-elastic emission intensity of the sensor element in either characterization: (a) the measure of the plurality of values is used to identify a magneto-elastic resonant frequency value for the sensor element; and (b) the measure of the plurality of successive values is done at a preselected magneto-elastic frequency.

Bachas, Leonidas G. (Inventor); Barrett, Gary (Inventor); Grimes, Craig A. (Inventor); Kouzoudis, Dimitris (Inventor); Schmidt, Stefan (Inventor)

2004-01-01

310

Development of bulk-scale and thin film magnetostrictive sensor  

NASA Astrophysics Data System (ADS)

Three key areas were investigated in this research. These are: (1) finite element modeling using modal analysis to better understand the mechanics of longitudinal vibration system, (2) thin film material Young's modulus measurement in a nondestructive manner by a magnetostrictive sensor, and (3) optimization of a deposition process for sputtering magnetostrictive thin films from Metglas 2826 MB ribbon and machining them into useful sensor platforms. We have verified the principle of operation for the longitudinal vibrating system through experimentation and comparison with numerical simulations of cantilevers, bridges, and beams. The results indicated that the governing vibration equation should use the plane-stress or biaxial modulus. Furthermore, the Poisson's ratio for Metglas 2826 MB was found to be 0.33. A resonating mechanical sensor was constructed from commercially available Metglas 2826 MB strip material and was used to measure Young's modulus of sputter deposited thin film material, e.g. Cu, Au, Al, Cr, Sn, In, SnAu (20/80 eutectic), and SiC, with a proposed measurement methodology. The determined Young's modulus values were comparable to those found in the literature. In addition, a finite element modeling analysis was employed to verify the Young's modulus determined by experimentation. Glass beads (size of ˜425 mum) were attached to freestanding (free-free ended) magnetostrictive sensors in order to simulate the attachment of target species. These mass-loading results indicated that the frequency shifts are sensitive to the location of the mass on the sensor's surface. Finite element analysis was conducted and ascertained that when a particle comparable in size to E. Coli O157 cell (mass in pico-gram range) attaches to sensor of 250 x 50 x 1.5 microns in size, a significant resonant frequency shift results, indicating that the sensor has the potential to detect the attachment of a single bacterium. These simulations also confirm that the resonant frequency shift is dependent on the location of the mass attachment along the longitudinal axis of the sensor. Finally, a process for depositing magnetostrictive thin film material from directly sputtering of Metglas 2826 MB ribbon was developed. Microscale sensors were fabricated with this film material. Dynamic testing of these microscale sensors was carried out on freestanding particles of the size 500 x 100 x 3 microns. The resonant frequency of these microfabricated particles was found to increase significantly in both magnitude and amplitude after the particle was annealed. A model was employed to explain why the magnetoelastic sensor behavior changed after annealing.

Liang, Cai

311

Microfabricated Chemical Gas Sensors and Sensor Arrays for Aerospace Applications  

NASA Technical Reports Server (NTRS)

Aerospace applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. In particular, factors such as minimal sensor size, weight, and power consumption are particularly important. Development areas which have potential aerospace applications include launch vehicle leak detection, engine health monitoring, and fire detection. Sensor development for these applications is based on progress in three types of technology: 1) Micromachining and microfabrication (Microsystem) technology to fabricate miniaturized sensors; 2) The use of nanocrystalline materials to develop sensors with improved stability combined with higher sensitivity; 3) The development of high temperature semiconductors, especially silicon carbide. This presentation discusses the needs of space applications as well as the point-contact sensor technology and sensor arrays being developed to address these needs. Sensors to measure hydrogen, hydrocarbons, nitrogen oxides (NO,), carbon monoxide, oxygen, and carbon dioxide are being developed as well as arrays for leak, fire, and emissions detection. Demonstrations of the technology will also be discussed. It is concluded that microfabricated sensor technology has significant potential for use in a range of aerospace applications.

Hunter, Gary W.

2005-01-01

312

Titanium dioxide-based carbon monoxide gas sensors: Effects of crystallinity and chemistry on sensitivity  

NASA Astrophysics Data System (ADS)

Among metal-oxide gas sensors which change electrical resistive properties upon exposure to target gasses, titanium dioxide (TiO2) has received attention for its sensitivity and stability during high temperature (>500°C) operation. However, due to the sensing mechanism sensitivity, selectivity, and stability remain as critical deficiencies to be resolved before these sensors reach commercial use. In this study, TiO2 thick films of approximately 30mum and thin films of approximately 1mum thick were fabricated to assess the influence of their material properties on gas sensing mechanism. Increased calcination temperature of TiO2 thick films led to grain growth, reduction in specific surface area, and particle-particle necking. These properties are known to degrade sensitivity; however the measured carbon monoxide (CO) gas response improved with increasing calcination temperature up to 800°C. It was concluded that the sensing improvement was due to increased crystallinity within the films. Sensing properties of TiO2 thin films of were also dependent on crystallization, however; due to the smaller volume of material, they reached optimized crystallization at lower temperatures of 650°C, compared to 800°C for thick films. Incorporation of tungsten (W) and nickel (Ni) ions into the films created donor and acceptor defect sites, respectively, within the electronic band gap of TiO2. The additional n-type defects in W-doped TiO 2 improved n-type CO response, while p-type defects in Ni-doped TiO 2 converted the gas response to p-type. Chemistry of thin films had a more significant impact on the electrical properties and gas response than did microstructure or crystallinity. Doped films could be calcined at higher temperatures and yet remain highly sensitive to CO. Thin films with p-n bi-layer structure were fabricated to determine the influence of a p-n junction on gas sensing properties. No effect of the junction was observed and the sensing response neared the average of the layers; however, electrical and gas response studies revealed that the majority of the conductivity and gas-surface reactions took place on the outer layer of the film. Further research is necessary to understand the influence of p-n junctions on the gas sensing behavior.

Seeley, Zachary Mark

313

Platinum and palladium doped tin oxide thick film sensors for sensing methane and hydrogen  

NASA Astrophysics Data System (ADS)

In this work, platinum (Pt) and palladium (Pd) doped SnO2 thick film sensors have been developed using solid state derived tin oxide powder. Thick film sensors were fabricated on a 1?x1? alumina substrate. The crystal structure and particle size are confirmed by X-ray diffraction (XRD) pattern. The fabricated sensors are tested for varying concentration (1-5%) of hydrogen and methane gas at different operating temperatures (200-350 °C). The effect of Pt and Pd doping have been analysed on different operating temperature, sensitivity and response/recovery time. The doping effects are also very important from view point of the gas selectivity. Based on the experimental results, we have observed the formation of tetragonal structure and particle size of the powders is drastically decreases from 26 to 19 nm after replacing the platinum dopant with palladium. Both the doped sensors have been found to be sensitive for hydrogen as compare to methane however, Pd-doped SnO2 sensor are most selective for hydrogen with very fast response and recovery time (20 s, 101 s) due to the small size effect.

Choudhary, Meenakshi; Mishra, V. N.; Dwivedi, R.

2013-01-01

314

Development of SiC Gas Sensor Systems  

NASA Technical Reports Server (NTRS)

Silicon carbide (SiC) based gas sensors have significant potential to address the gas sensing needs of aerospace applications such as emission monitoring, fuel leak detection, and fire detection. However, in order to reach that potential, a range of technical challenges must be overcome. These challenges go beyond the development of the basic sensor itself and include the need for viable enabling technologies to make a complete gas sensor system: electrical contacts, packaging, and transfer of information from the sensor to the outside world. This paper reviews the status at NASA Glenn Research Center of SiC Schottky diode gas sensor development as well as that of enabling technologies supporting SiC gas sensor system implementation. A vision of a complete high temperature microfabricated SiC gas sensor system is proposed. In the long-term, it is believed that improvements in the SiC semiconductor material itself could have a dramatic effect on the performance of SiC gas sensor systems.

Hunter, G. W.; Neudeck, P. G.; Okojie, R. S.; Beheim, G. M.; Thomas, V.; Chen, L.; Lukco, D.; Liu, C. C.; Ward, B.; Makel, D.

2002-01-01

315

Metal Oxide Gas Sensors: Sensitivity and Influencing Factors  

PubMed Central

Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above.

Wang, Chengxiang; Yin, Longwei; Zhang, Luyuan; Xiang, Dong; Gao, Rui

2010-01-01

316

Flexible carbon nanotube films for high performance strain sensors.  

PubMed

Compared with traditional conductive fillers, carbon nanotubes (CNTs) have unique advantages, i.e., excellent mechanical properties, high electrical conductivity and thermal stability. Nanocomposites as piezoresistive films provide an interesting approach for the realization of large area strain sensors with high sensitivity and low manufacturing costs. A polymer-based nanocomposite with carbon nanomaterials as conductive filler can be deposited on a flexible substrate of choice and this leads to mechanically flexible layers. Such sensors allow the strain measurement for both integral measurement on a certain surface and local measurement at a certain position depending on the sensor geometry. Strain sensors based on carbon nanostructures can overcome several limitations of conventional strain sensors, e.g., sensitivity, adjustable measurement range and integral measurement on big surfaces. The novel technology allows realizing strain sensors which can be easily integrated even as buried layers in material systems. In this review paper, we discuss the dependence of strain sensitivity on different experimental parameters such as composition of the carbon nanomaterial/polymer layer, type of polymer, fabrication process and processing parameters. The insights about the relationship between film parameters and electromechanical properties can be used to improve the design and fabrication of CNT strain sensors. PMID:24915183

Kanoun, Olfa; Müller, Christian; Benchirouf, Abderahmane; Sanli, Abdulkadir; Dinh, Trong Nghia; Al-Hamry, Ammar; Bu, Lei; Gerlach, Carina; Bouhamed, Ayda

2014-01-01

317

Flexible Carbon Nanotube Films for High Performance Strain Sensors  

PubMed Central

Compared with traditional conductive fillers, carbon nanotubes (CNTs) have unique advantages, i.e., excellent mechanical properties, high electrical conductivity and thermal stability. Nanocomposites as piezoresistive films provide an interesting approach for the realization of large area strain sensors with high sensitivity and low manufacturing costs. A polymer-based nanocomposite with carbon nanomaterials as conductive filler can be deposited on a flexible substrate of choice and this leads to mechanically flexible layers. Such sensors allow the strain measurement for both integral measurement on a certain surface and local measurement at a certain position depending on the sensor geometry. Strain sensors based on carbon nanostructures can overcome several limitations of conventional strain sensors, e.g., sensitivity, adjustable measurement range and integral measurement on big surfaces. The novel technology allows realizing strain sensors which can be easily integrated even as buried layers in material systems. In this review paper, we discuss the dependence of strain sensitivity on different experimental parameters such as composition of the carbon nanomaterial/polymer layer, type of polymer, fabrication process and processing parameters. The insights about the relationship between film parameters and electromechanical properties can be used to improve the design and fabrication of CNT strain sensors.

Kanoun, Olfa; Muller, Christian; Benchirouf, Abderahmane; Sanli, Abdulkadir; Dinh, Trong Nghia; Al-Hamry, Ammar; Bu, Lei; Gerlach, Carina; Bouhamed, Ayda

2014-01-01

318

Sensor for directly determining the exhaust gas recirculation rate—EGR sensor  

Microsoft Academic Search

Exhaust gas recirculation (EGR) is an effective means to reduce NOx emissions of internal combustion engines without increasing fuel consumption. Up to now, only complex procedures to determine the exhaust gas recirculation rate are available. Here, a novel sensor device is suggested that measures directly at one position and with only one single sensor device the concentration of a tracer

Ralf Moos; Burkhard Reetmeyer; Armin Hürland; Carsten Plog

2006-01-01

319

GAS MAIN SENSOR AND COMMUNICATIONS NETWORK SYSTEM  

SciTech Connect

Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the New York Gas Group (NYGAS), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. A prototype system was built for low-pressure cast-iron mains and tested in a spider- and serial-network configuration in a live network in Long Island with the support of Keyspan Energy, Inc. The prototype unit combined sensors capable of monitoring pressure, flow, humidity, temperature and vibration, which were sampled and combined in data-packages in an in-pipe master-slave architecture to collect data from a distributed spider-arrangement, and in a master-repeater-slave configuration in serial or ladder-network arrangements. It was found that the system was capable of performing all data-sampling and collection as expected, yielding interesting results as to flow-dynamics and vibration-detection. Wireless in-pipe communications were shown to be feasible and valuable data was collected in order to determine how to improve on range and data-quality in the future.

Hagen Schempf, Ph.D.

2003-02-27

320

Chemical Gas Sensors for Aeronautic and Space Applications  

NASA Technical Reports Server (NTRS)

Aeronautic and space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Two areas of particular interest are safety monitoring and emission monitoring. In safety monitoring, detection of low concentrations of hydrogen at potentially low temperatures is important while for emission monitoring the detection of nitrogen oxides, hydrogen, hydrocarbons and oxygen is of interest. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensors is based on progress in two types of technology: (1) Micromachining and microfabrication technology to fabricate miniaturized sensors. (2) The development of high temperature semiconductors, especially silicon carbide. The detection of each type of gas involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this microfabricated gas sensor technology make this general area of sensor development a field of significant interest.

Hunter, Gary W.; Chen, Liang-Yu; Neudeck, Philip G.; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai; Zhou, Huan-Jun

1997-01-01

321

Method of forming multi-element thin hot film sensors on polyimide film  

NASA Technical Reports Server (NTRS)

The invention comprises a method of forming a multi-element, thin hot film sensor on a polyimide film. The sensor is formed by first cleaning one surface of the polyimide. Then, under a continuous vacuum, the surface is simultaneously cleaned by ion bombardment while nickel is deposited by evaporation. The ion beam cleaning is discontinued and copper is then deposited to an initial thickness by evaporation without a break in the vacuum. The vacuum is then removed and a final thickness of copper is deposited by plating. Sensor patterns are then defined in the nickel and copper layers using conventional photolithography and etching techniques.

Hopson, Jr., Purnell (Inventor)

1996-01-01

322

Fabrication and characterization of all-thin-film magnetoelectric sensors  

Microsoft Academic Search

ac magnetic field sensors based on thin-film magnetoelectric (ME) devices operating at room temperature have been fabricated. The ME layers consist of a sol-gel derived Pb(Zr0.52Ti0.48)O3 film and a sputter deposited Fe0.7Ga0.3 film on Si cantilevers. The ME coupling is substantially improved by depositing a Pt layer at the interface. The ME coefficient up to 1.81 V\\/Oe cm is obtained

Peng Zhao; Zhenli Zhao; Dwight Hunter; Richard Suchoski; Chen Gao; Scott Mathews; Manfred Wuttig; Ichiro Takeuchi

2009-01-01

323

Ammonia sensor based on WO3 thin films  

NASA Astrophysics Data System (ADS)

WO3 thin films deposited using a simple method of vacuum evaporation has been investigated for their NH3 sensing properties. Effect of process parameters namely operating temperature, film thickness and amount of Au in the WO3 host matrix have been investigated and correlated with the observed sensitivity values to obtain the optimum sensor with improved sensing characteristics towards NH3. Pure WO3 films with thickness of 600 nm and the Au incorporated WO3 containing 0.034 wt.% Au were observed to exhibit a superior sensing property towards NH3.

Ramgir, Niranjan; Datta, Niyanta; Kaur, Manmeet; Kailasaganapati, S.; Debnath, A. K.; Aswal, D. K.; Gupta, S. K.

2012-06-01

324

Metal oxide nanowire gas sensors for indoor and outdoor environmental monitoring  

NASA Astrophysics Data System (ADS)

We present performance results of SnO2 and CuO nanowire gas sensor devices, where single and multi-nanowire device configurations have been employed in order to optimize sensor design. In particular the response to the target gases CO, H2, and H2S has been measured in dry and humid air; both the SnO2 and CuO nanowire sensors are able to detect CO in the low ppm concentration range, which is important for environmental monitoring. The CuO multi-nanowire devices show an extraordinary high response to H2S with sensitivity in the low ppb concentration. We present our developments of CMOS technology based micro-hotplates, which are employed as platform for gas sensitive thin films and nanowires. Potential heterogeneous integration of nanowires on the micro-hotplate chips as well as an approach towards gas sensor arrays is discussed. We conclude that CMOS integrated multi-nanowire gas sensors are highly promising candidates for the practical realization of multi-parameter sensor devices for indoor and outdoor environmental monitoring.

Köck, Anton; Brunet, Elise; Freudenberg, Oliver; Gamauf, Christoph; Kraft, Jochen; Mutinati, Giorgio C.; Maier, Thomas; Nemecek, Alexander; Schrank, Franz; Schrems, Martin; Siegele, Martin; Siegert, Jörg; Steinhauer, Stephan; Teva, Jordi

2013-05-01

325

Thin film devices used as oxygen partial pressure sensors  

NASA Technical Reports Server (NTRS)

Electrical conductivity of zinc oxide films to be used in an oxygen partial pressure sensor is measured as a function of temperature, oxygen partial pressure, and other atmospheric constituents. Time response following partial pressure changes is studied as a function of temperature and environmental changes.

Canady, K. S.; Wortman, J. J.

1970-01-01

326

Quick-Response Thin Film Platinum Temperature Sensor,  

National Technical Information Service (NTIS)

The newly developed quick-response thin-film platinum temperature sensor has the following features: (1) It has quick thermal response (0.03 seconds); (2) The temperature coefficient of the resistance conforms to 3850 ppm/degrees C of DIN43760. The stabil...

K. Ogata K. Matsumoto H. Tanigawa K. Onaka

1988-01-01

327

Fabrication of an uncooled infrared sensor using pyroelectric thin film  

NASA Astrophysics Data System (ADS)

In conventional IR-sensors, there are problems of needing cooler and sensing wavelength limitation. These problems can be achieved by using un-cooling thermal IR senors. However, they raise the problems of the attack of pyroelectric thin film layer during the etching of sacrificial layer as well as the thermal isolation of the IR detection layer. In order to fabricate uncooled IR-sensor using pyroelectric film, multilayer should be prepared pyroelectric thin film and thermally isolating membrane structure of square-shaped microstructures. We used the direct bonding technique to avoid the thermal loss by silicon substrate and the attack of pyroelectric thin film by etchant of the sacrificial layer. Metallic Pt layer used as a top and a bottom electrodes were deposited by E-beam sputtering method, while pyroelectric thin films were prepared Sol-Gel techniques. Because the pyroelectric thin film with c-axial orientation raised thermal polarization without the polling, the more integrated capability could be achieved. We investigated the characterized of the pyroelectric thin films: P-E loop, dielectric constant, XRD etc.

Park, Yun-Kwon; Ju, Byeong-Kwon; Park, Heung-Woo; Yoon, Young-Soo; Yom, Sang S.; Oh, Young-Jei; Park, Jung-Ho; Suh, Sang-Hee; Oh, Myung H.; Kim, Chul-Ju

1999-10-01

328

Optical Fiber Hydrogen Sensors with Pd\\/W03 Composite Thin Film by Magntron Co-Sputtering  

Microsoft Academic Search

A fiber-optic hydrogen gas sensor using composite palladium and tungsten trioxide (WO3) was proposed and characterized. This sensor utilizes the absorption of the evanescent field interaction in the clad of Pd\\/WO3 thin film which was prepared by magnetron co-sputtering process, coated on a silica core. Modulation of optical power intensity is observed, a clear increase of power with hydrogen and

Minghong Yang; Yan Sun; Dongsheng Zhang; Desheng Jiang

2009-01-01

329

Gas-sensitive properties of thin tin dioxide films under the influence of hydrogen sulfide  

NASA Astrophysics Data System (ADS)

In order to develop sensors for selective detection of hydrogen sulfide in the air, the characteristics of thin SnO2 films with various additives (Au, Pt) in the volume and deposited catalysts (Pt / Pd, Au) are studied. The films were obtained by magnetron sputtering. The sensor response to H2S (the ratio of the sensor conductivity G1 in the presence of hydrogen sulfide in the gas to the conductivity G0 in the clean air) is studied as a function of the operating temperature and gas concentration in the range 0.1-70 ppm. It is shown that the sensors with the addition of gold in the volume can be used to detect maximum permissible concentrations (7 ppm) of hydrogen sulfide in the working area after stabilization of the characteristics during long-term tests.

Sevast'yanov, E. Yu.; Maksimova, N. K.; Chernikov, E. V.; Firsov, A. A.

2012-11-01

330

Chemical Gas Sensors for Aeronautic and Space Applications 2  

NASA Technical Reports Server (NTRS)

Aeronautic and Space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Areas of most interest include launch vehicle safety monitoring emission monitoring and fire detection. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensor is based on progress two types of technology: 1) Micro-machining and micro-fabrication technology to fabricate miniaturized sensors. 2) The development of high temperature semiconductors, especially silicon carbide. Sensor development for each application involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this micro-fabricated gas sensor technology make this area of sensor development a field of significant interest.

Hunter, G. W.; Chen, L. Y.; Neudeck, P. G.; Knight, D.; Liu, C. C.; Wu, Q. H.; Zhou, H. J.; Makel, D.; Liu, M.; Rauch, W. A.

1998-01-01

331

Controlling a gas\\/odor plume-tracking robot based on transient responses of gas sensors  

Microsoft Academic Search

Gas sensors provide the artificial sense of smell for a mobile robot to track an airborne gas\\/odor plume and to locate its source. However, a slow response of gas sensors has been the major factor limiting the development of plume-tracking robots. This paper describes a new control algorithm that overcomes the limitation. The basic idea is to detect the onset

Hiroshi Ishida; Gouki Nakayama; Takamichi Nakamoto; Toyosaka Moriizumi

2002-01-01

332

Thin Film Ceramic Strain Sensor Development for Harsh Environments  

NASA Technical Reports Server (NTRS)

The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in propulsion system applications. In order to have a more passive method of negating changes of resistance due to temperature, an effort is underway at NASA GRC to develop high temperature thin film ceramic static strain gauges for application in turbine engines, specifically in the fan and compressor modules on blades. Other applications include on aircraft hot section structures and on thermal protection systems. The near-term interim goal of this research effort was to identify candidate thin film ceramic sensor materials to test for viability and provide a list of possible thin film ceramic sensor materials and corresponding properties to test for viability. This goal was achieved by conducting a thorough literature search for ceramics that have the potential for application as high temperature thin film strain gauges chemically and physically compatible and selecting potential candidate materials for with NASA GRC's microfabrication procedures and substrates.

Wrbanek, John D.; Fralick, Gustave

2007-01-01

333

Sensors and the Influence of Process Parameters and Thin Films  

NASA Astrophysics Data System (ADS)

Design of semiconductor silicon sensors is based on physical principles and the variation of geometry and material parameters. Normally in MEMS design a conversion method from non electrical input to an electrical output signal is chosen to get a good linear sensor. During miniaturization and increase of the accuracy the device behaves no more linear. For different function (e.c. sensitivity, resolution) and quality parameters (e.c. drift, burst pressure) of a device temperature coefficients (TC) nonlinearities, hysteresis and so on take place. Additional during characterization you find offsets and other effects, not described in your physical model of the device. The reason for this is that in thin films values, like the k-factor of metallic resistance, are influenced of process parameters, inhomogeneities in the capacity are influenced by process steps or geometry parameters have influence to void generation. For sensor design this all has to be modeled, that means we have to investigate microscopic effects. The influence of thin layers to function of a sensor is shown for Yaw rate sensors, pressure sensors, mass flow sensors and chemical sensors.

Krauss, Hans-Reiner

334

Transient hot-film sensor response in a shock tube  

NASA Technical Reports Server (NTRS)

Shock tube experiments were performed to determine the response of a hot-film sensor, mounted flush on the side wall of a shock tube, to unsteady flow behind a normal shock wave. The present experiments attempt to isolate the response of the anemometer due only to the change in convective heat transfer at the hot-film surface. The experiments, performed at low supersonic shock speeds in air, are described along with the data acquisition procedure. The change in convective heat transfer is deduced from the data and the results are compared with those from transient boundary layer theory and another set of experimental results. Finally, a transient local heat transfer coefficient is formulated for use as the forcing function in a hot-film sensor instrument model simulation.

Roberts, A. S., Jr.; Ortgies, K. R.; Gartenberg, E.

1989-01-01

335

Microprocessor controlled exhaust gas lambda sensor  

Microsoft Academic Search

The present paper describes a new design for a microprocessor controlled lambda sensor device. This device can be used for the external inspection and testing of an automobile's internal lambda sensor. The device is based on the Motorola 68HC11a1 microprocessor and utilises the linear signal from a new design oxygen sensor (linear air\\/fuel sensor, LAF) installed on it. This signal

P. N Botsaris; A Polyhroniadis

2000-01-01

336

SiC-Based Schottky Diode Gas Sensors  

NASA Technical Reports Server (NTRS)

Silicon carbide based Schottky diode gas sensors are being developed for high temperature applications such as emission measurements. Two different types of gas sensitive diodes will be discussed in this paper. By varying the structure of the diode, one can affect the diode stability as well as the diode sensitivity to various gases. It is concluded that the ability of SiC to operate as a high temperature semiconductor significantly enhances the versatility of the Schottky diode gas sensing structure and will potentially allow the fabrication of a SiC-based gas sensor arrays for versatile high temperature gas sensing applications.

Hunter, Gary W.; Neudeck, Philip G.; Chen, Liang-Yu; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai

1997-01-01

337

MWCNT-polymer composites as highly sensitive and selective room temperature gas sensors.  

PubMed

Multi-walled carbon nanotubes (MWCNTs)-polymer composite-based hybrid sensors were fabricated and integrated into a resistive sensor design for gas sensing applications. Thin films of MWCNTs were grown onto Si/SiO(2) substrates via xylene pyrolysis using the chemical vapor deposition technique. Polymers like PEDOT:PSS and polyaniline (PANI) mixed with various solvents like DMSO, DMF, 2-propanol and ethylene glycol were used to synthesize the composite films. These sensors exhibited excellent response and selectivity at room temperature when exposed to low concentrations (100 ppm) of analyte gases like NH(3) and NO(2). The effect of various solvents on the sensor response imparting selectivity to CNT-polymer nanocomposites was investigated extensively. Sensitivities as high as 28% were observed for an MWCNT-PEDOT:PSS composite sensor when exposed to 100 ppm of NH(3) and - 29.8% sensitivity for an MWCNT-PANI composite sensor to 100 ppm of NO(2) when DMSO was used as a solvent. Additionally, the sensors exhibited good reversibility. PMID:21451225

Mangu, Raghu; Rajaputra, Suresh; Singh, Vijay P

2011-05-27

338

Investigation into the hydrogen gas sensing mechanism of cubic silicon carbide resistive gas sensors  

Microsoft Academic Search

The hydrogen (H2) gas sensing mechanism driving 3C-SiC resistive gas sensors is investigated in this work in which two hypotheses are proposed. One hypothesis involves the surface adsorption of H2 on the sensor surface with the adsorbed molecules influencing the flow of current in a resistive gas sensor, termed the surface adsorption detection mechanism. The second hypothesis includes the transfer

Timothy J. Fawcett

2006-01-01

339

Investigation into the hydrogen gas sensing mechanism of 3C-SiC resistive gas sensors  

Microsoft Academic Search

The hydrogen (H2) gas sensing mechanism driving 3C-SiC resistive gas sensors is investigated in this work in which two hypotheses are proposed. One hypothesis involves the surface adsorption of H2 on the sensor surface with the adsorbed molecules influencing the flow of current in a resistive gas sensor, termed the surface adsorption detection mechanism. The second hypothesis includes the transfer

Timothy J Fawcett

2006-01-01

340

Gas Turbine Combustion Chambers with Film Evaporation.  

National Technical Information Service (NTIS)

The paper reports on an attempt to apply Meurer's film vaporization combustion method (M-method), originally developed for diesel motors, to the combustion chambers of gas turbines. (In the M-method, instead of distributing the fuel in the air, it is laid...

A. W. Hussmann

1968-01-01

341

Impedance spectroscopy of undoped and Cr-doped ZnO gas sensors under different oxygen concentrations  

NASA Astrophysics Data System (ADS)

Thin films of undoped and chromium (Cr)-doped zinc oxide (ZnO) were synthesized by RF reactive co-sputtering for oxygen gas sensing applications. The prepared films showed a highly c-axis oriented phase with a dominant (0 0 2) peak appeared at a Bragg angle of around 34.13 °, which was lower than that of the standard reference of ZnO powder (34.42 °). The peak shifted to a slightly higher angle with Cr doping. The operating temperature of the ZnO gas sensor was around 350 °C, which shifted to around 250 °C with Cr-doping. The response of the sensor to oxygen gas was enhanced by doping ZnO with 1 at.% Cr. Impedance spectroscopy analysis showed that the resistance due to grain boundaries significantly contributed to the characteristics of the gas sensor.

Al-Hardan, N.; Abdullah, M. J.; Aziz, A. Abdul

2011-08-01

342

GAS MAIN SENSOR AND COMMUNICATIONS NETWORK SYSTEM  

SciTech Connect

Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the New York Gas Group (NYGAS), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. In Phase II of this three-phase program, an improved prototype system was built for low-pressure cast-iron and high-pressure steel (including a no-blow installation system) mains and tested in a serial-network configuration in a live network in Long Island with the support of Keyspan Energy, Inc. The experiment was carried out in several open-hole excavations over a multi-day period. The prototype units (3 total) combined sensors capable of monitoring pressure, flow, humidity, temperature and vibration, which were sampled and combined in data-packages in an in-pipe master-repeater-slave configuration in serial or ladder-network arrangements. It was verified that the system was capable of performing all data-sampling, data-storage and collection as expected, yielding interesting results as to flow-dynamics and vibration-detection. Wireless in-pipe communications were shown to be feasible and the system was demonstrated to run off in-ground battery- and above-ground solar power. The remote datalogger access and storage-card features were demonstrated and used to log and post-process system data. Real-time data-display on an updated Phase-I GUI was used for in-field demonstration and troubleshooting.

Hagen Schempf

2004-09-30

343

Hydrogen sensors based on carbon nanotubes thin films  

Microsoft Academic Search

Single-walled carbon nanotubes (SWNTs) produced by arc-discharge have been researched as resistive gas sensors for H2 detection. Raw as well as modified single-walled carbon nanotubes were utilised as sensor material. Two types of modification treatments were carried out on the as grown SWNT material; chemical functionalization with palladium and doping with palladium by sputtering.CNTs were deposited on alumina substrates by

I. Sayago; E. Terrado; E. Lafuente; M. C. Horrillo; W. K. Maser; A. M. Benito; R. Navarro; E. P. Urriolabeitia; M. T. Martinez; J. Gutierrez

2005-01-01

344

Volatile organic compound gas sensor based on aluminum-doped zinc oxide with nanoparticle.  

PubMed

Thick film semiconductor gas sensors based on aluminum-doped zinc oxide (AZO) with nanoparticle size were fabricated to detect volatile organic compound (VOC) existed in building, especially, formaldehyde (HCHO) gas which was known as the cause of sick building syndrome. The sensing materials for screen printing were prepared using roll milling process with binder. The crystallite sizes of prepared materials were about 15 nm through X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Gas response characteristics were examined for formaldehyde (HCHO), benzene, carbon monoxide, carbon dioxide gas existing in building. In particular, the sensors showed responses to HCHO gas at sub ppm as a function of operating temperatures and gas concentrations. Also, we investigated sensitivity, repeativity, selectivity, and response time of sensor. The transients were very sharp, taking less than 2 s for 90% response. The sensor has shown very stable response at 350 degrees C and followed a very good behavior and showed 60% response in 50 ppb HCHO concentration at 350 degrees C operating temperatures. PMID:23882782

Choi, Nak-Jin; Lee, Hyung-Kun; Moon, Seung Eon; Yang, Woo Seok; Kim, Jongdae

2013-08-01

345

Polymeric foil optical waveguide with inkjet printed gas sensitive film for colorimetric sensing  

Microsoft Academic Search

The design of low-cost and low-power optical transducers on plastic foil for colorimetric gas sensors is proposed. The transducer was fabricated from PET or PEN foil on which polymeric micro-mirrors and colorimetric film were patterned using additive techniques. It consisted of a planar optical waveguide that was covered with an inkjet printed ammonia sensitive film for its evaluation. A parametric

J. Courbat; D. Briand; J. Wöllenstein; N. F. de Rooij

346

Design and Experimentation with Sandwich Microstructure for Catalytic Combustion-Type Gas Sensors  

PubMed Central

The traditional handmade catalytic combustion gas sensor has some problems such as a pairing difficulty, poor consistency, high power consumption, and not being interchangeable. To address these issues, integrated double catalytic combustion of alcohol gas sensor was designed and manufactured using silicon micro-electro-mechanical systems (MEMS) technology. The temperature field of the sensor is analyzed using the ANSYS finite element analysis method. In this work, the silicon oxide-PECVD-oxidation technique is used to manufacture a SiO2-Si3N2-SiO2 microstructure carrier with a sandwich structure, while wet etching silicon is used to form a beam structure to reduce the heat consumption. Thin-film technology is adopted to manufacture the platinum-film sensitive resistance. Nano Al2O3-ZrO-ThO is coated to format the sensor carrier, and the sensitive unit is dipped in a Pt-Pd catalyst solution to form the catalytic sensitive bridge arm. Meanwhile the uncoated catalyst carrier is considered as the reference unit, realizing an integrated chip based on a micro double bridge and forming sensors. The lines of the Pt thin-film resistance have been observed with an electronic microscope. The compensation of the sensitive material carriers and compensation materials have been analyzed using an energy spectrum. The results show that the alcohol sensor can detect a volume fraction between 0 and 4,500 × 10?6 and has good linear output characteristic. The temperature ranges from ?20 to +40 °C. The humidity ranges from 30% to 85% RH. The zero output of the sensor is less than ±2.0% FS. The power consumption is ?0.2 W, and both the response and recovery time are approximately 20 s.

Gu, Jun-Tao; Zhang, Yong-De; Jiang, Jin-Gang

2014-01-01

347

Design and experimentation with sandwich microstructure for catalytic combustion-type gas sensors.  

PubMed

The traditional handmade catalytic combustion gas sensor has some problems such as a pairing difficulty, poor consistency, high power consumption, and not being interchangeable. To address these issues, integrated double catalytic combustion of alcohol gas sensor was designed and manufactured using silicon micro-electro-mechanical systems (MEMS) technology. The temperature field of the sensor is analyzed using the ANSYS finite element analysis method. In this work, the silicon oxide-PECVD-oxidation technique is used to manufacture a SiO2-Si3N2-SiO2 microstructure carrier with a sandwich structure, while wet etching silicon is used to form a beam structure to reduce the heat consumption. Thin-film technology is adopted to manufacture the platinum-film sensitive resistance. Nano Al2O3-ZrO-ThO is coated to format the sensor carrier, and the sensitive unit is dipped in a Pt-Pd catalyst solution to form the catalytic sensitive bridge arm. Meanwhile the uncoated catalyst carrier is considered as the reference unit, realizing an integrated chip based on a micro double bridge and forming sensors. The lines of the Pt thin-film resistance have been observed with an electronic microscope. The compensation of the sensitive material carriers and compensation materials have been analyzed using an energy spectrum. The results show that the alcohol sensor can detect a volume fraction between 0 and 4,500 × 10(-6) and has good linear output characteristic. The temperature ranges from -20 to +40 °C. The humidity ranges from 30% to 85% RH. The zero output of the sensor is less than ±2.0% FS. The power consumption is ?0.2 W, and both the response and recovery time are approximately 20 s. PMID:24625742

Gu, Jun-Tao; Zhang, Yong-De; Jiang, Jin-Gang

2014-01-01

348

Novel aspect in grain size control of nanocrystalline diamond film for thin film waveguide mode resonance sensor application.  

PubMed

Nanocrystalline diamond (NCD) thin film growth was systematically investigated for application for the thin film waveguide mode resonance sensor. The NCD thin film was grown on the Si wafer or on the SiO2-coated sapphire substrate using the hot filament chemical vapor deposition (HFCVD). The structural/optical properties of the samples were characterized by the high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS), near edge X-ray absorption fine structure (NEXAFS), X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. The waveguide modes of the NCD layer were studied by prism coupler technique using laser (wavelength: 632.8 nm) with varying incident angle. A novel aspect was disclosed in the grain size dependence on the growth temperature at the relatively low methane concentration in the precursor gas, which was important for optical property: the grain size increased with decreasing growth temperature, which was contrary to the conventional knowledge prevailing in the microcrystalline diamond (MCD) domain. We have provided discussions to reconcile such observation. An optical waveguide mode resonance was demonstrated in the visible region using the microstructure-controlled transparent NCD thin film waveguide, which provided a strong potential for the waveguide mode resonance sensor applications. PMID:24195713

Lee, Hak-Joo; Lee, Kyeong-Seok; Cho, Jung-Min; Lee, Taek-Sung; Kim, Inho; Jeong, Doo Seok; Lee, Wook-Seong

2013-11-27

349

A Thin Film Multifunction Sensor for Harsh Environments  

NASA Technical Reports Server (NTRS)

The status of work at NASA Glenn Research Center to develop a minimally intrusive integrated sensor to provide realtime measurement of strain, heat flux and flow in high temperature environments is presented in this paper. The sensor can be beneficial as a single package to characterize multiple stress and strain modes simultaneously on materials and components during engine development and validation. A major technical challenge is to take existing individual gauge designs and modify them into one integrated thin film sensor. Ultimately, the goal is to develop the ability to deposit the sensors directly onto internal engine parts or on a small thin substrate that can be attached to engine components. Several prototype sensors constructed of platinum, platinum-rhodium alloy, and alumina on constant-strain alumina beams have been built and bench-tested. The technical challenges of the design. construction, and testing are discussed. Data from the preliminary testing of the sensor array is presented. The future direction for the sensor development is discussed as well.

Wrbanek, John D.; Fralick, Gustave C.; Martin, Lisa C.; Blaha, Charles A.

2001-01-01

350

Aluminum-doped TiO 2 nano-powders for gas sensors  

Microsoft Academic Search

Nano-powders of pure and Al-doped TiO2 ceramics were synthesized using a citrate–nitrate auto combustion method. Powders were then used to make thick film gas sensors to measure selectivity and sensitivity in CO and O2 environment. Titanyl nitrate solution was prepared using commercial TiO2 powder, hydrofluoric acid (HF) and concentrated nitric acid (HNO3). An optimized ratio of citrate to nitrate was

Young Jin Choi; Zachary Seeley; Amit Bandyopadhyay; Susmita Bose; Sheikh A. Akbar

2007-01-01

351

Non-Noble-Metal Dopants in Tin Oxide Gas Sensor for Detection of Isobutane  

Microsoft Academic Search

SnO2 films were prepared from paste and sol-gel by spinning on substrate. The dopants were non-noble metals at 0.5-4 mole%, it included Al, La, Nd, Mn, Ni, Cu, Sb, In, Nb, Si and Fe. The effects of these dopants towards isobutane sensitivity of SnO2 gas sensor were investigated. Increases in isobutene sensitivity were achieved with 0.5%Fe and 1%Si for paste-derived

Paisan Setasuwon

352

Multifunctional sensing film used for fiber optic cholesterol sensor  

NASA Astrophysics Data System (ADS)

In this paper, by using ethyl silicate, ethanol and fluorescence indicator as the precursors, the multifunctional optic biosensing (MOBS) film containing cholesterol oxidase and the fluorescence indicator was prepared by sol-gel method. This biosensing film has both the function of biocatalyst and oxygen biosensing and can be used as the effective biosensing materials for fiber optic cholesterol sensor. The fiber optical cholesterol sensor based on fluorescence quenching was designed and fabricated using lock-in amplifying technology to realize the detection of cholesterol concentration. The experimental results showed that the best precursor proportion in volume ratio is: ethyl silicate: ethanol: 0.01 M HCl = 5: 8: 1.6. The drying rate of the sol could be controlled by using formamide as the controlling drier. When 16% of formamide were added in the mixing system, the cracks of the film could be reduced greatly and the immobilization of cholesterol oxidase and the fluorescence indicator could be improved effectively. A linear relationship between phase delay ? and the cholesterol concentration was observed in the range of 100 to 500 mg/dL. Since the cholesterol concentration is in the range of 140 to 200 mg/dL in the blood of healthy people, it will be possible for the sensor to be used in clinical detection. The biosensor with MOBS film has the response time of about 30 s, which is rather fast for a biosensor, and the relative deviation of +/-5.03%. This biosensor also has good stability.

Wang, Bin; Huang, Jun; Li, Mingtian; Zhou, Xuan

2008-12-01

353

Gas sensors based on SAW narrow aperture devices  

Microsoft Academic Search

A new configuration of surface acoustic wave (SAW) gas sensors based on SAW waveguide devices with relatively narrow aperture of several wavelengths is suggested. This suggested configuration permits to impart to SAW sensor a new feature such as a certain electronic tuning of chemical selectivity (without sensitive coating) by applying electric voltage between this waveguide and two planar electrodes closely

Yu. V. Gulyaev; R. G. Kryshtal; A. V. Medved; V. V. Shemet; V. E. Zemlyakov

2000-01-01

354

Integrated sensor head for gas analysis via atomic emission spectroscopy  

Microsoft Academic Search

We report about design, fabrication, and experimental characterization of a compact sensor head for gas analysis via atomic emission spectroscopy. The novelty of our approach is the integration of a micro-hollow cathode structure for plasma generation and an optical collector on a common planar micro systems platform. The sensor head is designed for a fiber optic spectrometer. Elliptically-shaped reflector segments

Matthias Gruber; Michael Bohling; Martin Mogl; Hans Knuppertz; Holger Winkelmann

2010-01-01

355

Optochemical sensor for determining ozone based on novel soluble indigo dyes immobilised in a highly permeable polymeric film.  

PubMed

An optochemical ozone sensor is described that has been manufactured by immobilisation of novel soluble indigo derivatives in permeable transparent polymeric films of polydimethylsiloxane-polycarbonate copolymer. From a number of investigated indigo derivatives, 4,4',7,7'-tetraalkoxyindigo 9 has been selected for optimal sensitivity and specificity of ozone detection. A linear calibration for ozone can be obtained in the range between 0.01 and 0.5 ppm. The limit of quantitation is 0.03 ppm, and the accuracy exceeds 8%. It takes about 134 s to measure the relatively low occupational exposure concentration of 0.1 ppm. A reduction of the sensor response time could be achieved through application of double-sided coated sensors instead of single-sided variants. The stability of the sensors and the effect of external parameters like relative humidity (RH), temperature and gas flow on the sensor response have been investigated. The sensor response is affected by varying the gas flow or temperature; however, humidity in the range between 0 and 90% RH does not affect sensor response. The indigo derivative 9 remained stable inside the polymeric film and no chemical reaction, crystallisation or leaching occurred during 10 months of observation. Proper choice of indicator dye and polymeric material and successful application of kinetic evaluation method for the exposure experiments determine the desired features of the sensor. PMID:15986207

Alexy, Marcin; Voss, Gundula; Heinze, Jürgen

2005-08-01

356

Development of an ammonia gas sensor  

Microsoft Academic Search

Copper (I) bromide (CuBr) thin films for ammonia detection are prepared by two different techniques: (1) magnetron sputtering and (2) chemical or electrochemical oxidation of copper in presence of bromine ions. The microstructure of the films is related to these processes. The electrical properties of these films are studied and the temperature dependence of the bulk conductivity is in agreement

Marc Bendahan; Pascal Lauque; Jean-Luc Seguin; Khalifa Aguir; Philippe Knauth

2003-01-01

357

Turbine Blade Temperature Measurements Using Thin Film Temperature Sensors  

NASA Technical Reports Server (NTRS)

The development of thin film temperature sensors is discussed. The technology for sputtering 2 micron thin film platinum versus platinum 10 percent rhodium thermocouples on alumina forming coatings was improved and extended to applications on actual turbine blades. Good adherence was found to depend upon achieving a proper morphology of the alumina surface. Problems of adapting fabrication procedures to turbine blades were uncovered, and improvements were recommended. Testing at 1250 K at one atmosphere pressure was then extended to a higher Mach No. (0.5) in combustor flow for 60 hours and 71 thermal cycles. The mean time to failure was 47 hours accumulated during 1 hour exposures in the combustor. Calibration drift was about 0.1 percent per hour, attributable to oxidation of the rhodium in the thin films. An increase in film thickness and application of a protective overcoat are recommended to reduce drift in actual engine testing.

Grant, H. P.; Przybyszewski, J. S.; Claing, R. G.

1981-01-01

358

Studying the Effect of Deposition Conditions on the Performance and Reliability of MEMS Gas Sensors  

PubMed Central

In this paper, the reliability of a micro-electro-mechanical system (MEMS)-based gas sensor has been investigated using Three Dimensional (3D) coupled multiphysics Finite Element (FE) analysis. The coupled field analysis involved a two-way sequential electrothermal fields coupling and a one-way sequential thermal-structural fields coupling. An automated substructuring code was developed to reduce the computational cost involved in simulating this complicated coupled multiphysics FE analysis by up to 76 percent. The substructured multiphysics model was then used to conduct a parametric study of the MEMS-based gas sensor performance in response to the variations expected in the thermal and mechanical characteristics of thin films layers composing the sensing MEMS device generated at various stages of the microfabrication process. Whenever possible, the appropriate deposition variables were correlated in the current work to the design parameters, with good accuracy, for optimum operation conditions of the gas sensor. This is used to establish a set of design rules, using linear and nonlinear empirical relations, which can be utilized in real-time at the design and development decision-making stages of similar gas sensors to enable the microfabrication of these sensors with reliable operation.

Sadek, Khaled; Moussa, Walied

2007-01-01

359

Intrinsic fiber optical gas sensor based on surface plasmon resonance spectroscopy  

NASA Astrophysics Data System (ADS)

A miniaturized fiber optical sensor based on surface plasmon resonance spectroscopy is investigated in view of the detection of organic solvent vapors, particularly tetrachloroethene. Surface plasmons are excited on a silver coated multimode fiber by polychromatic light, and the resonant excitation is detected as a resonant absorption band in the measured output spectrum. When the analyte is absorbed in a thin gas-sensitive polysiloxane film deposited on the silver layer the polymer film changes its thickness and its refractive index. These changes result in a wavelength shift of the resonant curve depending on the analyte gas concentration. Theoretical considerations about the sensing effect are made and resonance curves were computer-simulated. Based on this simulation the layout of all sensor parameters was optimized. The sensor shows an excellent response to tetrachloroethene with a response time of two seconds and high reporducibility. Using self-assembling monolayers on the silver surface a long-term stability of more than three months is obtained. The sensor shows low cross sensitivities less than 1% to other solvent vapors like aceton and ethanol, furthermore, the influence of humidity is very low. This miniaturized fiber optical sensor in combination with an easy-to-handle and non-sophisticated measuring and evaluation unit is excellently suitable for the remote sensing of special organic solvent vapors.

Niggemann, Matthias; Katerkamp, Andreas; Pellmann, Maria; Bolsmann, Peter; Reinbold, Joerg; Cammann, Karl

1995-09-01

360

Electrochemically Functionalized Single-Walled Carbon Nanotube Gas Sensor  

Microsoft Academic Search

We demonstrate a facile fabrication method to make chemical gas sensors using single-walled carbon nanotubes (SWNT) electrochemically functionalized with polyaniline (PANI). The potential advantage of this method is to enable targeted functionalization with different materials to allow for creation of high-density individually addressable nanosensor arrays. PANI-SWNT network based sensors were tested for on-line monitoring of ammonia gas. The results show

Ting Zhang; Bong-Young Yoo

2006-01-01

361

Langasite for high-temperature acoustic wave gas sensors  

Microsoft Academic Search

Langasite (La3Ga5SiO14), a piezoelectric material with no phase transitions to 1470°C, holds promise as a high-sensitivity crystal microbalance gas sensor platform. In order to successfully implement langasite acoustic wave gas sensors, electrical losses at elevated temperatures need be minimized. The electrical conductivity of langasite is characterized as a function of oxygen partial pressure for temperatures of 700–1000°C and correlated with

Huankiat Seh; Harry L. Tuller; Holger Fritze

2003-01-01

362

Micromachined Thin-Film Sensors for SOI-CMOS Co-Integration  

NASA Astrophysics Data System (ADS)

Co-integration of sensors with their associated electronics on a single silicon chip may provide many significant benefits regarding performance, reliability, miniaturization and process simplicity without significantly increasing the total cost. Micromachined Thin-Film Sensors for SOI-CMOS Co-integration covers the challenges and interests and demonstrates the successful co-integration of gas flow sensors on dielectric membrane, with their associated electronics, in CMOS-SOI technology. We firstly investigate the extraction of residual stress in thin layers and in their stacking and the release, in post-processing, of a 1 ?m-thick robust and flat dielectric multilayered membrane using Tetramethyl Ammonium Hydroxide (TMAH) silicon micromachining solution.

Laconte, Jean; Flandre, D.; Raskin, Jean-Pierre

363

Properties of thin films for high temperature flow sensors  

NASA Technical Reports Server (NTRS)

Requirements of material parameters of high temperature flow sensors are identified. Refractory metal silicides offer high temperature sensitivity and high frequency response and are stable up to 1000 C. Intrinsic semiconductors of high band gap are also considered as sensor elements. SiC and diamond are identified. Combined with substrates of low thermal and electrical conductivity, such as quartz or Al2O3, these materials meet several requirements of high sensitivity and frequency response. Film deposition and patterning techniques suitable for these materials are identified.

Albin, Sacharia

1991-01-01

364

Selective mixed potential ammonia exhaust gas sensor  

Microsoft Academic Search

Novel selective ammonia sensors with high potential for long-term stability in harsh exhaust environments are introduced. The sensor bases on the mixed potential effect. In contrast to common sensors, the electrode functionalities electrical conductivity, selective catalytic activity, and electrochemical activity combined with long-term stability are separated. For that reason, one of the two electrodes is covered by a well-known porous

Daniela Schönauer; Kerstin Wiesner; Maximilian Fleischer; Ralf Moos

2009-01-01

365

Correlation between XPS, Raman and TEM measurements and the gas sensitivity of Pt and Pd doped SnO2 based gas sensors  

Microsoft Academic Search

Nanocrystalline thick-film SnO2 sensors with different dopants were fabricated by an optimized screen printing process and subsequent annealing. Powders\\u000a were used as starting materials which were prepared by a wet chemical process from SnCl4. Microanalysis was performed of both, the precursors and the final sensor materials with their different annealing conditions.\\u000a Gas sensing tests with CO, CH4 and NO2 in

J. Kappler; N. Bârsan; U. Weimar; A. Dièguez; J. L. Alay; A. Romano-Rodriguez; J. R. Morante; W. Göpel

1998-01-01

366

Post treatment of plasma-polymerized SnOx organic-like films with poly ethylene glycol for improving CO gas sensitivity.  

PubMed

In this study, a new room temperature type gas sensor device based on plasma deposition of tetramethyltin (TMT) and O2 organically hybridized film followed by post treatment on the deposited film was developed for improving CO gas sensitivity and distinguishing from methane, butane, and carbon monoxide gases in the test environment. Plasma deposited SnOx thin film was first produced from TMT and O2 gas mixtures at room temperature, and then post treatments on the SnOx thin films were carried out by either spin coating with poly ethylene glycol (PEG) or surface grafting with p-styrenesulfonic acid sodium salt (Nass). It was found that the gas sensor spin coating post treated with PEG exhibits linear response to CO gas with the sensitivity not affected by methane and butane gases. For CO concentrations ranging from 30 to 650 ppm, steep change in the sensor resistance can be detected without warming up the sensor. PMID:22629938

Liao, Shu-Chuan; Wu, Hsin-Ming; Tsao, Yu-Chia; Lin, Hong-Ru; Chen, Ko-Shao; Chen, Wei-Yu

2012-02-01

367

Co-polymer films for sensors  

NASA Technical Reports Server (NTRS)

Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

Ryan, Margaret A. (Inventor); Homer, Margie L. (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Jewell, April D. (Inventor); Shevade, Abhijit V. (Inventor); Manatt, Kenneth S. (Inventor); Taylor, Charles (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor)

2010-01-01

368

Producing CCD imaging sensor with flashed backside metal film  

NASA Technical Reports Server (NTRS)

A backside illuminated CCD imaging sensor for reading out image charges from wells of the array of pixels is significantly improved for blue, UV, far UV and low energy x-ray wavelengths (1-5000.ANG.) by so overthinning the backside as to place the depletion edge at the surface and depositing a thin transparent metal film of about 10.ANG. on a native-quality oxide film of less than about 30.ANG. grown on the thinned backside. The metal is selected to have a higher work function than that of the semiconductor to so bend the energy bands (at the interface of the semiconductor material and the oxide film) as to eliminate wells that would otherwise trap minority carriers. A bias voltage may be applied to extend the frontside depletion edge to the interface of the semiconductor material with the oxide film in the event there is not sufficient thinning. This metal film (flash gate), which improves and stabilizes the quantum efficiency of a CCD imaging sensor, will also improve the QE of any p-n junction photodetector.

Janesick, James R. (Inventor)

1988-01-01

369

CCD imaging sensor with flashed backside metal film  

NASA Technical Reports Server (NTRS)

A backside illuminated CCD imaging sensor for reading out image charges from wells of the array of pixels is significantly improved for blue, UV, far UV and low energy x-ray wavelengths (1-5000.ANG.) by so overthinning the backside as to place the depletion edge at the surface and depositing a thin transparent metal film of about 10.ANG. on a native-quality oxide film of less than about 30.ANG. grown on the thinned backside. The metal is selected to have a higher work function than that of the semiconductor to so bend the energy bands (at the interface of the semiconductor material and the oxide film) as to eliminate wells that would otherwise trap minority carriers. A bias voltage may be applied to extend the frontside depletion edge to the interface of the semiconductor material with the oxide film in the event there is not sufficient thinning. This metal film (flash gate), which improves and stabilizes the quantum efficiency of a CCD imaging sensor, will also improve the QE of any p-n junction photodetector.

Janesick, James R. (Inventor)

1991-01-01

370

Application of a sensor array based on capillary-attached conductive gas sensors for odor identification  

Microsoft Academic Search

An electronic nose based on an array of capillary-attached conductive gas sensors was fabricated. The identification ability of the developed structure was investigated by employing different categories of simple and complex odor databases. Feature data sets were generated from the dynamic and steady state responses of the sensor array to the applied odor databases. Combinations of different feature extraction and

Behzad Bahraminejad; Shahnor Basri; Maryam Isa; Zarida Hambali

2010-01-01

371

NOVEL GAS SENSORS FOR HIGH-TEMPERATURE FOSSIL FUEL APPLICATIONS  

SciTech Connect

SRI is developing ceramic-based microsensors for detection of exhaust gases such as NO, NO{sub 2}, and CO in advanced combustion and gasification systems. The sensors detect the electrochemical activity of the exhaust gas species on catalytic electrodes and are designed to operate at high temperatures, elevated pressures, and corrosive environments typical of large power generation exhausts. Under this research project we are developing sensors for multiple gas detection in a single package along with data acquisition and control software and hardware. The sensor package can be easily integrated into online monitoring systems for active emission control. This report details the research activities performed from October 2003 to April 2004.

Palitha Jayaweera

2004-05-01

372

Wide-range (0.33%-100%) 3C-SiC resistive hydrogen gas sensor development  

Microsoft Academic Search

Silicon carbide (SiC) resistive hydrogen gas sensors have been fabricated and tested. NiCr planar ohmic contacts were deposited on both a 4 mum 3C-SiC epitaxial film grown on n-type Si(001) and directly on Si to form the resistive sensor structures. Detection at concentrations as low as 0.33% and as high as 100% (H2 in Ar) was observed with the 3C-SiC

Timothy J. Fawcett; John T. Wolan; Rachael L. Myers; Jeremy Walker; Stephen E. Saddow

2004-01-01

373

Wide-range (0.33%–100%) 3C–SiC resistive hydrogen gas sensor development  

Microsoft Academic Search

Silicon carbide (SiC) resistive hydrogen gas sensors have been fabricated and tested. NiCr planar ohmic contacts were deposited on both a 4 ?m 3C–SiC epitaxial film grown on n-type Si(001) and directly on Si to form the resistive sensor structures. Detection at concentrations as low as 0.33% and as high as 100% (H2 in Ar) was observed with the 3C–SiC

Timothy J. Fawcett; John T. Wolan; Rachael L. Myers; Jeremy Walker; Stephen E. Saddow

2004-01-01

374

Nano-assembled films for taste sensor application.  

PubMed

An artificial taste sensor based on different types of ultra-thin films of conducting polymers (a special class of plastics that can conduct electricity) and their mixture with a lipid-like material has been able to mimic the human palate. In addition, this "electronic tongue" has been successfully employed in the analysis of tastants, suppression effects, and commercial beverages throughout AC measurements (impedance spectroscopy) in a relatively low-cost, simple, and efficient way. PMID:12752211

Riul, Antonio Riul; Malmegrim, Roger R; Fonseca, Fernando J; Mattoso, Luiz H C

2003-05-01

375

Biosensors based on the thin-film magnetoresistive sensors  

Microsoft Academic Search

The review considered the state-of-the-art in the development of devices for detection of the agents of disease on the basis\\u000a of the Lab on a chip (LOC) biosensors whose detecting element is a matrix of thin-film anisotropic magnetoresistive (AMR),\\u000a magnetoresistive (GMR), or spin-tunnel magnetoresistive (STMR) magnetic field sensors based on the multi-chip planar technology.\\u000a Data were presented on the nanospherical

S. I. Kasatkin; N. P. Vasil’eva; A. M. Murav’ev

2010-01-01

376

Tantalum oxide thin films as protective coatings for sensors  

Microsoft Academic Search

Reactively sputtered tantalum oxide thin films have been investigated as protective coatings for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140 is lower than 0.008 . Etching in liquids with pH values in the range from pH 2 to 11 have generally given

Carsten Christensen; Roger de Reus; Siebe Bouwstra

1999-01-01

377

Tantalum oxide thin films as protective coatings for sensors  

Microsoft Academic Search

Reactively sputtered tantalum oxide thin-films have been investigated as protective coating for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140°C is lower than 0.008 Å\\/h. Etching in liquids with pH values in the range from pH 2-11 have generally given etch rates below

Carsten Christensen; Roger de Reus; S. Bouwstra

1999-01-01

378

Optical sensors and multisensor arrays containing thin film electroluminescent devices  

DOEpatents

Optical sensor, probe and array devices for detecting chemical biological, and physical analytes. The devices include an analyte-sensitive layer optically coupled to a thin film electroluminescent layer which activates the analyte-sensitive layer to provide an optical response. The optical response varies depending upon the presence of an analyte and is detected by a photodetector and analyzed to determine the properties of the analyte.

Aylott, Jonathan W. (Ann Arbor, MI); Chen-Esterlit, Zoe (Ann Arbor, MI); Friedl, Jon H. (Ames, IA); Kopelman, Raoul (Ann Arbor, MI); Savvateev, Vadim N. (Ames, IA); Shinar, Joseph (Ames, IA)

2001-12-18

379

Method of Forming a Hot Film Sensor System on a Model  

NASA Technical Reports Server (NTRS)

A method of forming a hot film sensor directly on a model is provided. A polyimide solution is sprayed onto the model. The model so sprayed is then heated in air. The steps of spraying and heating are repeated until a polyimide film of desired thickness is achieved on the model. The model with the polyimide film thereon is then thoroughly dried in air. One or more hot film sensors and corresponding electrical conducting leads are then applied directly onto the polyimide film.

Tran, Sang Q. (Inventor)

1998-01-01

380

Theory for a gas composition sensor based on acoustic properties  

NASA Technical Reports Server (NTRS)

Sound travelling through a gas propagates at different speeds and its intensity attenuates to different degrees depending upon the composition of the gas. Theoretically, a real-time gaseous composition sensor could be based on measuring the sound speed and the acoustic attenuation. To this end, the speed of sound was modelled using standard relations, and the acoustic attenuation was modelled using the theory for vibrational relaxation of gas molecules. The concept for a gas composition sensor is demonstrated theoretically for nitrogen-methane-water and hydrogen-oxygen-water mixtures. For a three-component gas mixture, the measured sound speed and acoustic attenuation each define separate lines in the composition plane of two of the gases. The intersection of the two lines defines the gas composition. It should also be possible to use the concept for mixtures of more than three components, if the nature of the gas composition is known to some extent.

Phillips, Scott; Dain, Yefim; Lueptow, Richard M.

2003-01-01

381

Reflectance Infrared Spectroscopy on Operating Surface Acoustic Wave Chemical Sensors During Exposure to Gas-Phase Analytes  

SciTech Connect

We have developed instrumentation to enable the combination of surface acoustic wave (SAW) sensor measurements with direct, in-situ molecular spectroscopic measurements to understand the response of the SAW sensors with respect to the interfacial chemistry of surface-confined sensing films interacting with gas-phase analytes. Specifically, the instrumentation and software was developed to perform in-situ Fourier-transform infrared external-reflectance spectroscopy (FTIR-ERS) on operating SAW devices during dosing of their chemically modified surfaces with analytes. By probing the surface with IR spectroscopy during gas exposure, it is possible to understand in unprecedented detail the interaction processes between the sorptive SAW coatings and the gaseous analyte molecules. In this report, we provide details of this measurement system, and also demonstrate the utility of these combined measurements by characterizing the SAW and FTIR-ERS responses of organic thin-film sensor coatings interacting with gas-phase analytes.

Hierlemann, A.; Hill, M.; Ricco, A.J.; Staton, A.W.; Thomas, R.C.

1999-01-11

382

Design and modeling of metal oxide gas sensors  

NASA Astrophysics Data System (ADS)

Detailed theoretical models are presented, and used to facilitate the design of industrial metal oxide gas sensors. By modeling both the sensing mechanisms and the conduction process, these methods optimize the sensitivity and selectivity. A phenomenological approach to the operation of metal oxide gas sensors, the Integrated Reaction Conduction (IRC) model, is introduced. The IRC model consolidates the surface reaction kinetics and electrical conduction through the granular sensor microstructure. A simple relation is established between the sensing mechanism reaction energies and the sensing behavior of n-type oxide sensors. The adsorption and oxidation reaction energies for anatase-phase based TiO2 sensors are extracted from comparisons with experimental data. By predicting the effects of dopants, temperature, and sintering on the sensor response, the IRC model foretells improvement of the sensitivity and other gas sensor properties. The depletion width prior to reducing gas exposure in an n-type metal oxide sensor is calculated by combining the known defect chemistry and the various phenomena determining electron depletion near the oxide surface. These include the charged surface of adsorbed oxygen ions, dopant segregation, and ionic defect accumulation. The sensor response is found to enhance if the depletion width is comparable to the grain size. Affecting the initial depletion width via dopants or ionic defect equilibration provides an alternate route towards sensor response optimization. The Polychromatic Percolation Model (PPM) is introduced, and facilitates the design of a selective n/p composite sensor by predicting the sensor response as a function of the n-type/p-type composition. Conduction through an n-type/p-type composite containing randomly distributed and oriented grains is characterized as a percolation phenomenon, where the overall resistance of the material combines contributions from n-type and p-type pathways. The composite microstructure governs the relative fraction of each pathway type and its respective percolation threshold, while the effective resistance through each pathway is calculated using experimentally measured resistances of single-phase n-type and p-type materials. PPM model calculations match the experimentally measured response of an anatase/rutile TiO2 composite gas sensor, and the conductivity of a ZnO/CuO n/p composite. Using the predictions of the PPM model, a selective n/p composite sensor may be designed.

Chwieroth, Brian Stewart

383

Diamond thin film temperature and heat-flux sensors  

NASA Technical Reports Server (NTRS)

Diamond film temperature and heat-flux sensors are developed using a technology compatible with silicon integrated circuit processing. The technology involves diamond nucleation, patterning, doping, and metallization. Multi-sensor test chips were designed and fabricated to study the thermistor behavior. The minimum feature size (device width) for 1st and 2nd generation chips are 160 and 5 micron, respectively. The p-type diamond thermistors on the 1st generation test chip show temperature and response time ranges of 80-1270 K and 0.29-25 microseconds, respectively. An array of diamond thermistors, acting as heat flux sensors, was successfully fabricated on an oxidized Si rod with a diameter of 1 cm. Some problems were encountered in the patterning of the Pt/Ti ohmic contacts on the rod, due mainly to the surface roughness of the diamond film. The use of thermistors with a minimum width of 5 micron (to improve the spatial resolution of measurement) resulted in lithographic problems related to surface roughness of diamond films. We improved the mean surface roughness from 124 nm to 30 nm by using an ultra high nucleation density of 10(exp 11)/sq cm. To deposit thermistors with such small dimensions on a curved surface, a new 3-D diamond patterning technique is currently under development. This involves writing a diamond seed pattern directly on the curved surface by a computer-controlled nozzle.

Aslam, M.; Yang, G. S.; Masood, A.; Fredricks, R.

1995-01-01

384

Renewable liquid film-based electrochemical sensor for gaseous hydroperoxides.  

PubMed

Electrochemical sensors for hydroperoxides based on thin flowing films were investigated. The sensor is composed of two segments of Nafion tubing put on a silver wire. A small portion of the silver wire is exposed and is chloridized to function as the reference electrode. One Nafion segment has a Pt-wire coil wrapped on it to function as the counter electrode and the other has a similar Pt-Rh wire coil that functions as the working electrode. A collection solution flows as a thin film on the sensor surface and also functions as the collection medium. Hydrogen peroxide and cumene hydroperoxide were examined as test compounds. The former can be oxidatively determined with a Pt-Rh electrode over a large range (ppb-ppm) without any significant influence of relative humidity. By using a technique to stop the liquid flow, the sensitivity can be further improved. Cumene hydroperoxide, an industrially important hydroperoxide, can be determined easily with a relative precision of better than 5% in the vapor phase over simulated process reaction mixtures containing percentage levels of the analyte by reduction on a Pd electrode. The sensor is simple and inexpensive to fabricate and requires only a suitably equipped personal computer for operation. PMID:18966780

Huang, H; Dasgupta, P K

1997-04-01

385

Conjugated polymer films for gas separations  

Microsoft Academic Search

Permeabilities for a series of gases through free-standing films of the conjugated polymer polyaniline are reported. A remarkable selectivity has been achieved for important gas pairs including hydrogen-nitrogen, oxygen-nitrogen, and carbon dioxide-methane. The selectivity values of 3,590 for Hâ\\/Nâ, 30 for Oâ\\/Nâ, and 336 for COâ\\/CHâsurpass the highest previously reported values of 313, 16, and 60 for the nonconjugated polymers

M. R. Anderson; B. R. Mattes; H. Reiss; R. B. Kaner

1991-01-01

386

Highly selective gas sensor arrays based on thermally reduced graphene oxide  

NASA Astrophysics Data System (ADS)

The electrical properties of reduced graphene oxide (rGO) have been previously shown to be very sensitive to surface adsorbates, thus making rGO a very promising platform for highly sensitive gas sensors. However, poor selectivity of rGO-based gas sensors remains a major problem for their practical use. In this paper, we address the selectivity problem by employing an array of rGO-based integrated sensors instead of focusing on the performance of a single sensing element. Each rGO-based device in such an array has a unique sensor response due to the irregular structure of rGO films at different levels of organization, ranging from nanoscale to macroscale. The resulting rGO-based gas sensing system could reliably recognize analytes of nearly the same chemical nature. In our experiments rGO-based sensor arrays demonstrated a high selectivity that was sufficient to discriminate between different alcohols, such as methanol, ethanol and isopropanol, at a 100% success rate. We also discuss a possible sensing mechanism that provides the basis for analyte differentiation.

Lipatov, Alexey; Varezhnikov, Alexey; Wilson, Peter; Sysoev, Victor; Kolmakov, Andrei; Sinitskii, Alexander

2013-05-01

387

Compact Laser Multi-gas Spectral Sensors for Spacecraft Systems  

NASA Technical Reports Server (NTRS)

The objective of this research effort has been the development of a new gas sensor technology to meet NASA requirements for spacecraft and space station human life support systems for sensitive selective and real time detection of trace gas species in the mid-infrared spectral region.

Tittel, Frank K.

1997-01-01

388

Development of SiC Gas Sensor Systems.  

National Technical Information Service (NTIS)

Silicon carbide (SiC) based gas sensors have significant potential to address the gas sensing needs of aerospace applications such as emission monitoring, fuel leak detection, and fire detection. However, in order to reach that potential, a range of techn...

G. W. Hunter P. G. Neudeck R. S. Okojie G. M. Beheim V. Thomas L. Chen D. Lukco C. C. Liu B. Ward D. Makel

2002-01-01

389

High sensitive tellurium based NO 2 gas sensor  

Microsoft Academic Search

For the first time it is shown, that tellurium based thin films exhibit high sensitivity to nitrogen dioxide at room temperature. The resistance of the tellurium films decreases reversibly in the presence of NO2. The sensitivity of this device depends on the gas concentration and it increases to lower concentrations less than 3ppm. The response time is considerably short and

D. Tsiulyanu; S. Marian; V. Miron; H.-D. Liess

2001-01-01

390

Optical-integrated NH3 sensor design using WO3 thin tllms: influence of gas adsorption and chromic effects  

Microsoft Academic Search

We propose a new model for the design of optical-integrated (OI) sensor, composed of a surface waveguide covered with a sensitive material (SM) deposited at the surface in the form of thin films. Commonly these last are metallic oxides which becomes highly absorbent in the presence of the gas to be detected. In this way, the optical signal propagating in

Hugo E. Lazcano Hernández; Celia Sánchez Pérez; Augusto García Valenzuela

2008-01-01

391

Microhotplate-based silicon gas sensor arrays with linear temperature gradient for wine quality monitoring  

NASA Astrophysics Data System (ADS)

In this work, we describe the design implementation, validated by experimental results, of an innovative gas sensor array for wine quality monitoring. The main innovation of this integrated array deals with the simultaneous outputs, from a single chip on TO-12 socket, of 8 different signals coming from a WO3 thin film structure heated in a linear temperature gradient mode, allowing an overall evaluation of gas sensing properties of the material in a 100°C-wide window, typically from 300 to 400°C. The implemented sensitive layer is a WO3 film deposed by RF-sputtering. Preliminary tests of gas sensing showed good responses to the target analytes for the specific application (1-heptanol, 3-methyl butanol, benzaldehyde and ethyl-hexanoate).

Adami, Andrea; Lorenzelli, Leandro; Guarnieri, Vittorio; Zen, Mario; Francioso, Luca; Siciliano, Pietro; Forleo, A.; Taurino, A. M.; Agnusdei, Giuseppe

2005-07-01

392

Fabrication and characterization of all-thin-film magnetoelectric sensors  

NASA Astrophysics Data System (ADS)

ac magnetic field sensors based on thin-film magnetoelectric (ME) devices operating at room temperature have been fabricated. The ME layers consist of a sol-gel derived Pb(Zr0.52Ti0.48)O3 film and a sputter deposited Fe0.7Ga0.3 film on Si cantilevers. The ME coupling is substantially improved by depositing a Pt layer at the interface. The ME coefficient up to 1.81 V/Oe cm is obtained at the mechanical resonant frequency of 333 Hz and at dc bias magnetic field of 90 Oe. Clear reduction in the substrate clamping effect is observed as the Si cantilever thickness is systematically reduced down to 35 ?m.

Zhao, Peng; Zhao, Zhenli; Hunter, Dwight; Suchoski, Richard; Gao, Chen; Mathews, Scott; Wuttig, Manfred; Takeuchi, Ichiro

2009-06-01

393

A monolithic integrated 4 × 4 tin oxide gas sensor array with on-chip multiplexing and differential readout circuits  

NASA Astrophysics Data System (ADS)

This paper presents a monolithic 4 × 4 tin oxide gas sensor array together with on-chip multiplexing and differential read-out circuitry. A robust fabrication process focusing on the integration of the CMOS circuitry and the microelectromechanical systems (MEMS) structure is first described. The gas sensor uses a surface micro-machined micro-hotplate based structure. Platinum is selected as the material of choice for both the micro heater and the sensor's electrodes, for its good thermal stability and compatibility with the sensing film. Different post-treatments are used to modify the characteristics of the tin oxide gas sensors hence improving the sensor's selectivity of the overall sensor array. Furthermore, in contrast to the conventional voltage divider read-out technique, a novel differential read-out circuit (DRC) for tin oxide gas sensors is proposed. The DRC applies a constant current to drive the sensor and uses a unit-gain single stage amplifier (inverter) to generate a fully differential output, directly from the voltage drop across the sensor. The output of the DRC is simply proportional to the difference between the voltage on the two electrodes of the sensor but not to the transistor parameters such as mobility and threshold voltage, neither to the supply voltage. The monolithic sensor array and its pre-processing circuitry have been implemented in our in-house 5 ?m process. Experimental results showed good linearity at the output of the DRC for a wide range of sensor resistance variation (over 20 M?). The fabricated micro-hotplate sensor array was tested for four target gases. Results show good sensitivity and interesting thermal characteristic leading to only 15.5 mW power consumption for 300 °C operating temperature.

Guo, Bin; Bermak, Amine; Chan, Philip C. H.; Yan, Gui-Zhen

2007-01-01

394

Sensor validation and fusion for gas turbine vibration monitoring  

NASA Astrophysics Data System (ADS)

Vibration monitoring is an important practice throughout regular operation of gas turbine power systems and, even more so, during characterization tests. Vibration monitoring relies on accurate and reliable sensor readings. To obtain accurate readings, sensors are placed such that the signal is maximized. In the case of characterization tests, strain gauges are placed at the location of vibration modes on blades inside the gas turbine. Due to the prevailing harsh environment, these sensors have a limited life and decaying accuracy, both of which impair vibration assessment. At the same time bandwidth limitations may restrict data transmission, which in turn limits the number of sensors that can be used for assessment. Knowing the sensor status (normal or faulty), and more importantly, knowing the true vibration level of the system all the time is essential for successful gas turbine vibration monitoring. This paper investigates a dynamic sensor validation and system health reasoning scheme that addresses the issues outlined above by considering only the information required to reliably assess system health status. In particular, if abnormal system health is suspected or if the primary sensor is determined to be faulted, information from available "sibling" sensors is dynamically integrated. A confidence expresses the complex interactions of sensor health and system health, their reliabilities, conflicting information, and what the health assessment is. Effectiveness of the scheme in achieving accurate and reliable vibration evaluation is then demonstrated using a combination of simulated data and a small sample of a real-world application data where the vibration of compressor blades during a real time characterization test of a new gas turbine power system is monitored.

Yan, Weizhong; Goebel, Kai F.

2003-08-01

395

40 Å Platinum-porous SiC gas sensor: Investigation sensing properties of H2 gas  

NASA Astrophysics Data System (ADS)

The present paper reports on a new structure for H2 gas sensing based on thin porous silicon carbide (PSiC) films. The PSiC layer has been formed by electrochemical etching of SiC films previously deposited onto p-type silicon substrate by pulsed laser deposition (PLD) using 6H-SiC target. Current-voltage (I-V) and current-time (I-t) characteristics have been measured. A thin platinum (Pt) film (40 Å thickness) deposited onto PSiC layer has been used as a catalytic metal. The Schottky diode parameters such as ideality factor (n), barrier height (?Bp) and series resistance (RS) have been evaluated under different concentrations of H2 gas. The experimental results show that upon exposure to H2 gas the barrier height, the ideality factor and the series resistance change significantly. The different changes in the electrical parameters of the structure (increase and decrease as a function of the H2 concentration) have been explained by the formation of two inversion layers. The first one forms as soon as the gas is in contact with the sensor and the second when the concentration reaches 90 ppm. Subsequently, the effect of gas concentration on the maximum sensitivity value of the sensor has been investigated. A high sensitivity (?I/I) value around 86% is found at about 1 V bias voltage. In addition, the response and recovery times were determined to be around 55 s and 160 s, respectively. Finally, the structure shows a reversible response for low gas concentration at room temperature.

Keffous, A.; Cheriet, A.; Hadjersi, T.; Boukennous, Y.; Gabouze, N.; Boukezzata, A.; Belkacem, Y.; Kechouane, M.; Kerdja, T.; Menari, H.; Berouaken, M.; Talbi, L.; Ouadah, Y.

2013-01-01

396

Feasibility of wireless gas detection with an FMCW RADAR interrogation of passive RF gas sensor  

Microsoft Academic Search

The feasibility of the remote measurement of gas detection from an RF gas sensor has been experimentally investigated. It consists of a Frequency-Modulated Continuous-Wave (FMCW) RADAR interrogation of an antenna loaded by the passive sensor. The frequency band of the RADAR [28.8-31GHz] allows the detection of the resonant frequencies of Whispering Gallery Modes that are sensitive to gas concentration. Reported

Hamida Hallil; F. Chebila; P. Menini; P. Pons; H. Aubert

2010-01-01

397

Ultramultiple roundtrips of surface acoustic wave on sphere realizing innovation of gas sensors.  

PubMed

A thin beam of wave usually diverges due to diffraction, which is a limitation of any device using such waves. However, a surface acoustic wave (SAW) on a sphere with an appropriate aperture does not diverge but is naturally collimated, realizing ultramultiple roundtrips along an equator of the sphere. This effect is caused by the balance between diffraction and focusing on a spherical surface, and it enables realization of high-performance ball SAW sensors. The advantage of ball SAW is most fully appreciated when applied to a very thin sensitive film for which the multiple-roundtrip enhances the sensitivity, but the attenuation loss is not very large. It is exemplified in a hydrogen gas sensor that realizes a wide sensing range of 10 ppm to 100% for the first time, and realizes relatively fast response time of 20 s without heating the sensitive film. PMID:16615584

Yamanaka, Kazushi; Ishikawa, Satoru; Nakaso, Noritaka; Takeda, Nobuo; Sim, Dong Youn; Mihara, Tsuyoshi; Mizukami, Akio; Satoh, Ichitaro; Akao, Shingo; Tsukahara, Yusuke

2006-04-01

398

Optical fiber Bragg grating hydrogen sensor based on evanescent-field interaction with palladium thin-film transducer  

NASA Astrophysics Data System (ADS)

Fiber Bragg grating (FBG) sensors in single-mode optical fibers are widely applied for measurement of temperature and strain. If exposing FBG sensors to an external analyte by planar side-polishing technique of the fiber, evanescent-field interaction yields a Bragg wavelength shift also by changing the refractive index of the analyte. Deposition of sensor-specific transducer layers on the side-polished fiber can specify this spectrally encoding and network-capable optochemical fiber Bragg grating refractometry to the monitoring of specific substances, absorbed gases and vapors. In this paper, the sensor principle is demonstrated for the example of a hydrogen gas sensor based on a palladium thin-film transducer. Hydrogen in 0.1-4% volume concentration range can be monitored by the spectral shift of the Bragg wavelength, which is caused by the decreasing complex refractive index of Pd with increasing absorption of hydrogen.

Schroeder, Kerstin; Ecke, Wolfgang; Willsch, Reinhardt

2009-10-01

399

The gas-sensing properties of WO3-x thin films deposited via the atmospheric pressure chemical vapour deposition (APCVD) of WCl6 with ethanol  

NASA Astrophysics Data System (ADS)

The use of the APCVD reaction of WCl6 with ethanol to produce tungsten oxide films (3600-6700 nm thick) for use as gas sensors is presented. The response of these films to varying concentrations of ethanol and NO2 at varying temperatures has been examined. A comparison of the CVD sensors to a thick film (~60 µm) screen-printed sensor has shown that the CVD sensors have a faster rate of response, a stable sensing response and faster return to baseline with no drift at the conditions examined.

Ashraf, Sobia; Blackman, Christopher S.; Naisbitt, Simon C.; Parkin, Ivan P.

2008-02-01

400

Application of a sensor array based on capillary-attached conductive gas sensors for odor identification  

NASA Astrophysics Data System (ADS)

An electronic nose based on an array of capillary-attached conductive gas sensors was fabricated. The identification ability of the developed structure was investigated by employing different categories of simple and complex odor databases. Feature data sets were generated from the dynamic and steady state responses of the sensor array to the applied odor databases. Combinations of different feature extraction and classification methods were used to detect target gases. Validation of each technique was evaluated. Achievements of the study proved high classification rates of the fabricated e-nose in odor identification. It was indicated that gas identification is possible by applying the early selected portion of transient responses of the developed sensor array. The ability of the mentioned structure in analyzing gas mixtures was also investigated. The results presented high accuracy in the classification of gas mixtures.

Bahraminejad, Behzad; Basri, Shahnor; Isa, Maryam; Hambali, Zarida

2010-08-01

401

Alpha-Particle Gas-Pressure Sensor  

NASA Technical Reports Server (NTRS)

An approximate model was developed to establish design curves for the saturation region and a more complete model developed to characterize the current-voltage curves for an alpha-particle pressure sensor. A simple two-parameter current-voltage expression was developed to describe the dependence of the ion current on pressure. The parameters are the saturation-current pressure coefficient and mu/D, the ion mobility/diffusion coefficient. The sensor is useful in the pressure range between 0.1 and 1000 mb using a 1 - mu Ci(241) Am source. Experimental results, taken between 1 and up to 200 mb, show the sensor operates with an anode voltage of 5 V and a sensitivity of 20 fA/mb in nitrogen.

Buehler, M. C.; Bell, L. D.; Hecht, M. H.

1996-01-01

402

Thin Film Heat Flux Sensor Development for Ceramic Matrix Composite (CMC) Systems  

NASA Technical Reports Server (NTRS)

The NASA Glenn Research Center (GRC) has an on-going effort for developing high temperature thin film sensors for advanced turbine engine components. Stable, high temperature thin film ceramic thermocouples have been demonstrated in the lab, and novel methods of fabricating sensors have been developed. To fabricate thin film heat flux sensors for Ceramic Matrix Composite (CMC) systems, the rough and porous nature of the CMC system posed a significant challenge for patterning the fine features required. The status of the effort to develop thin film heat flux sensors specifically for use on silicon carbide (SiC) CMC systems with these new technologies is described.

Wrbanek, John D.; Fralick, Gustave C.; Hunter, Gary W.; Zhu, Dongming; Laster, Kimala L.; Gonzalez, Jose M.; Gregory, Otto J.

2010-01-01

403

Pattern recognition of gas sensor array using characteristics of impedance  

Microsoft Academic Search

In this paper, impedance variations of SnO2-based gas sensor array are measured in gases. Back propagation algorithm of pattern recognition [1,2] is used to distinguish a species and concentration of gases with analog signals of impedance variation from sensor array. When the impedance variation presents as the quantities of rising and falling time to 100kHz pulse input signal of a

Byung-Su Joo; Nak-Jin Choi; Yun-Su Lee; Jun-Woo Lim; Bong-Hwi Kang; Duk-Dong Lee

2001-01-01

404

Designing Real Nanotube-Based Gas Sensors  

NASA Astrophysics Data System (ADS)

Using a combination of density functional theory and recursive Green‘s functions techniques, we present a full description of a large scale sensor, accounting for disorder and different coverages. Here, we use this method to demonstrate the functionality of nitrogen-rich carbon nanotubes as ammonia sensors as an example. We show how the molecules one wishes to detect bind to the most relevant defects on the nanotube, describe how these interactions lead to changes in the electronic transport properties of each isolated defect, and demonstrate that there are significative resistance changes even in the presence of disorder, elucidating how a realistic nanosensor works.

Rocha, A. R.; Rossi, M.; Fazzio, A.; da Silva, Antonio J. R.

2008-05-01

405

Physical characteristics of polyimide films for flexible sensors  

NASA Astrophysics Data System (ADS)

Physical characteristics of polyimide films, including optical, micro/nano mechanical, and thermophysical characteristics were investigated using a photometric, a nanoindentation, and a thermomechanical analyzer for applications in flexible sensors. Experimental results show that UV light cannot transmit into the polyimide films. The transmittances, with a maximum of about 86%, at VIS and near IR lights decrease with increasing PI film thicknesses. The mechanical characteristics were determined using tensile, bending moment, and nanoindentation testing. The stress-strain curve approximated bilinear characteristics, the load-unload bending moment exhibited hysteresis, and nanoindentation generated elastic energy dissipation in the loading-unloading region. Nanoindentation showed an almost uniform hardness and a reduced Young’s modulus of about 0.181±0.03 and 3.21±0.06 GPa, respectively, when the penetrating depth was more than about 2 ?m. Thermophysical characteristics were greatly influenced on 8.3 and 25 ?m specimens due to the higher relaxation of thin PI films. The thermal expansion remained steady when the thickness was over 50 ?m. The results show that PI films have potential in flexible sensing and higher temperature fabrication.

Chang, Wen-Yang; Fang, Te-Hua; Lin, Yu-Cheng

2008-08-01

406

SEMICONDUCTOR DEVICES: Chlorine gas sensors using hybrid organic semiconductors of PANI/ZnPcCl16  

NASA Astrophysics Data System (ADS)

PANI/ZnPcCl16 (polyaniline doped with sulfosalicylic acid/hexadecachloro zinc phthalocyanine) powders were vacuum co-deposited onto Si substrates, where Pt interdigitated electrodes were made by micromachining. The PANI/ZnPcCl16 films were characterized and analyzed by SEM, and the influencing factors on its intrinsic performance were analyzed and sensitivities of the sensors were investigated by exposure to chlorine (Cl2) gas. The results showed that powders prepared with a stoichiometric ratio of (ZnPcCl16)0.6(PANI)0.4 had a preferential sensitivity to Cl2 gas, superior to those prepared otherwise; the optimal vacuum co-deposition conditions for the films are a substrate temperature of 160 °C, an evaporation temperature of 425 °C and a film thickness of 75 nm; elevating the operation temperature (above 100 °C) or increasing the gas concentration (over 100 ppm) would improve the response characteristics, but there should be upper levels for each. Finally, the gas sensing mechanism of PANI/ZnPcCl16 films was also discussed.

Tingping, Lei; Yunbo, Shi; Wenlong, Lü; Yang, Liu; Wei, Tao; Pengliang, Yuan; Liwei, Lin; Daoheng, Sun; Liquan, Wang

2010-08-01

407

On-chip fabrication of SnO 2nanowire gas sensor: The effect of growth time on sensor performance  

Microsoft Academic Search

In this works, we report on the on-chip fabrication of SnO2-nanowire gas sensors by selective growth of the nanowires on Pt interdigitated at different grown time lengths. The gas-sensing properties of the on-chip fabricated sensors were characterized using liquefied petroleum gas (LPG) and NH3 gas at different operating temperatures. The effect of growth time on sensor performances was systematically investigated

Le Viet Thong; Nguyen Duc Hoa; Dang Thi Thanh Le; Do Thanh Viet; Phuong Dinh Tam; Anh-Tuan Le; Nguyen Van Hieu

2010-01-01

408

Optical Sensors Based on Single Arm Thin Film Waveguide Interferometer  

NASA Technical Reports Server (NTRS)

All the goals of the research effort for the first year were met by the accomplishments. Additional efforts were done to speed up the process of development and construction of the experimental gas chamber which will be completed by the end of 1997. This chamber incorporates vacuum sealed multimode optical fiber lines which connect the sensor to the remote light source and signal processing equipment. This optical fiber line is a prototype of actual optical communication links connecting real sensors to a control unit within an aircraft or spacecraft. An important problem which we are planning to focus on during the second year is coupling of optical fiber line to the sensor. Currently this problem is solved using focusing optics and prism couplers. More reliable solutions are planned to be investigated.

Sarkisov, Sergey S.

1997-01-01

409

Gas composition determination in an air conditioned system using a sensor array: characterization of three different TGS sensors  

Microsoft Academic Search

The determination of the atmosphere gas composition in any application by gas sensors implies a very well-known response to all the sensors used to obtain this information. The aim of our work is to detect forane R134a or carbon dioxide or a mixture of these two gases in dry synthetic air. For these reasons, the first studied sensor was the

Frédéric Sarry; Martine Lumbreras

1999-01-01

410

MEMS device for mass market gas and chemical sensors  

NASA Astrophysics Data System (ADS)

Gas and chemical sensors are used in many applications. Industrial health and safety monitors allow companies to meet OSHA requirements by detecting harmful levels of toxic or combustible gases. Vehicle emissions are tested during annual inspections. Blood alcohol breathalizers are used by law enforcement. Refrigerant leak detection ensures that the Earth's ozone layer is not being compromised. Industrial combustion emissions are also monitored to minimize pollution. Heating and ventilation systems watch for high levels of carbon dioxide (CO2) to trigger an increase in fresh air exchange. Carbon monoxide detectors are used in homes to prevent poisoning from poor combustion ventilation. Anesthesia gases are monitored during a patients operation. The current economic reality is that two groups of gas sensor technologies are competing in two distinct existing market segments - affordable (less reliable) chemical reaction sensors for consumer markets and reliable (expensive) infrared (IR) spectroscopic sensors for industrial, laboratory, and medical instrumentation markets. Presently high volume mass-market applications are limited to CO detectros and on-board automotive emissions sensors. Due to reliability problems with electrochemical sensor-based CO detectors there is a hesitancy to apply these sensors in other high volume applications. Applications such as: natural gas leak detection, non-invasive blood glucose monitoring, home indoor air quality, personal/portable air quality monitors, home fire/burnt cooking detector, and home food spoilage detectors need a sensor that is a small, efficient, accurate, sensitive, reliable, and inexpensive. Connecting an array of these next generation gas sensors to wireless networks that are starting to proliferate today creates many other applications. Asthmatics could preview the air quality of their destinations as they venture out into the day. HVAC systems could determine if fresh air intake was actually better than the air in the house. Internet grocery delivery services could check for spoiled foods in their clients' refrigerators. City emissions regulators could monitor the various emissions sources throughout the area from their desk to predict how many pollution vouchers they will need to trade in the next week. We describe a new component architecture for mass-market sensors based on silicon microelectromechanical systems (MEMS) technology. MEMS are micrometer-scale devices that can be fabricated as discrete devices or large arrays, using the technology of integrated circuit manufacturing. These new photonic bandgap and MEMS fabricataion technologies will simplify the component technology to provide high-quality gas and chemical sensors at consumer prices.

Kinkade, Brian R.; Daly, James T.; Johnson, Edward A.

2000-08-01

411

A miniaturized carbon dioxide gas sensor based on infrared absorption  

NASA Astrophysics Data System (ADS)

A miniaturized sensor for measuring carbon dioxide (CO 2) gas concentration is developed based on infrared absorption. A novel space-double-beam optical probe is designed, which consists of an infrared source, an air chamber, an infrared receiving device, and two sapphire windows. The air chamber is modified by incorporating a parabolic-shaped receiving-light cone to effectively improve the signal-to-noise ratio of the sensor. Four rectangle holes are arranged around the air chamber, and diffusive sampling is adopted to collect gas into the air chamber. The infrared source works between ON and OFF states. The interference of background light is eliminated by subtracting the measured value in the ON state from the OFF state. The measurement model of the sensor is established based on the Lambert-Beer law and the working principle of the sensor. The partial least squares method is applied to calibrate the measurement model. The sensor has a volume of 80 mm ( L)×78 mm ( W)×35 mm ( H), a weight of 200 g, a power consumption of 1.5 W, and a response time of 2.5 s. The experimental results show that the measurement accuracy of the sensor is 0.026% with a measurement range of 0-3% for CO 2 gas concentration.

Zhang, Guangjun; Li, Yaping; Li, Qingbo

2010-12-01

412

Pattern Recognition for Selective Odor Detection with Gas Sensor Arrays  

PubMed Central

This paper presents a new pattern recognition approach for enhancing the selectivity of gas sensor arrays for clustering intelligent odor detection. The aim of this approach was to accurately classify an odor using pattern recognition in order to enhance the selectivity of gas sensor arrays. This was achieved using an odor monitoring system with a newly developed neural-genetic classification algorithm (NGCA). The system shows the enhancement in the sensitivity of the detected gas. Experiments showed that the proposed NGCA delivered better performance than the previous genetic algorithm (GA) and artificial neural networks (ANN) methods. We also used PCA for data visualization. Our proposed system can enhance the reproducibility, reliability, and selectivity of odor sensor output, so it is expected to be applicable to diverse environmental problems including air pollution, and monitor the air quality of clean-air required buildings such as a kindergartens and hospitals.

Kim, Eungyeong; Lee, Seok; Kim, Jae Hun; Kim, Chulki; Byun, Young Tae; Kim, Hyung Seok; Lee, Taikjin

2012-01-01

413

Passivated thick film catalytic type H 2 sensor operating at low temperature  

Microsoft Academic Search

Thick film catalytic sensors operable at a temperature of 120°C have been developed to measure hydrogen concentration (HC) in 0–10% (v\\/v) range. The sensors consists of a glass encapsulated Pt-heater coated with a catalytic thick film and a compensating element without the active film. An rf sputtered PTFE thin film on active element has been found to improve resistance of

V. R. Katti; A. K. Debnath; S. C. Gadkari; S. K. Gupta; V. C. Sahni

2002-01-01

414

Solid State Gas Sensor for Volatile Organic Vapours  

NASA Astrophysics Data System (ADS)

Nano Crystalline ZnO powders were synthesized by a Solvothermal method using propan-1ol as the reaction medium. Wurtzite-type ZnO powder has been synthesized by a Solvothermal method at low temperature with an aim to obtain nano crystalline ZnO and to study its ethanol and methanol gas sensing properties have been examined by nano crystalline Zinc oxide sensor in this study. The resulting powder was characterized by FT-IR and Powder X-ray diffraction (XRD) techniques which reveals the structure without any significant change in the cell parameters and the synthesized ZnO having average crystallite size of 10-25 nm, respectively. The gas sensor was made on alumina substrate. Various preparation parameters are optimized for maximum sensitivity. The sensitivity for different volatile organic gases such as ethanol and methanol was investigated at different temperatures and concentrations. The sensors fabricated from the nano sized powder exhibited higher ethanol sensing properties at a working temperature of 300° C and similar characteristics were observed for methanol also. ZnO based gas sensor exhibits high sensitivity for ethanol and methanol. Results demonstrated that the ZnO were promising for gas sensor with best sensing characteristics.

Pasha, Sk. Khadeer; Chidambaram, K.

2009-06-01

415

Optical control and diagnostics sensors for gas turbine machinery  

NASA Astrophysics Data System (ADS)

There exists a vast range of optical techniques that have been under development for solving complex measurement problems related to gas-turbine machinery and phenomena. For instance, several optical techniques are ideally suited for studying fundamental combustion phenomena in laboratory environments. Yet other techniques hold significant promise for use as either on-line gas turbine control sensors, or as health monitoring diagnostics sensors. In this paper, we briefly summarize these and discuss, in more detail, some of the latter class of techniques, including phosphor thermometry, hyperspectral imaging and low coherence interferometry, which are particularly suited for control and diagnostics sensing on hot section components with ceramic thermal barrier coatings (TBCs).

Trolinger, James D.; Jenkins, Thomas P.; Heeg, Bauke

2012-10-01

416

Structure of Palladium Nanoclusters for Hydrogen Gas Sensors  

SciTech Connect

Palladium nanoclusters produced by inert gas aggregation/magnetron sputtering are used as building blocks for the construction of nano electronic devices with large surface to volume ratios that can be used as sensitive hydrogen gas sensors in fuel cells and in petrochemical plants. X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and high resolution transmission electron microscopy (HRTEM) have been used to characterize the structure, lattice constant, particle diameter and oxide thickness of the palladium nanoclusters in order to understand the operation of these sensors. Grazing incidence XRD (GIXRD) of heat treated Pd clusters has shown that the palladanite structure forms at elevated temperatures.

Stevens, K.J.; Ingham, B.; Toney, M.F.; Brown, S.A.; Lassesson, A.; /SLAC, SSRL /Canterbury U.

2009-05-11

417

The exploitation of thin film coatings for fibre sensors for the application of chemical sensing  

NASA Astrophysics Data System (ADS)

We report on the use of thin film coatings, both single and multi-layered, deposited on the flat side of a lapped, D-shaped fibre to enhance the sensitivity of two kinds of surface plasmon resonance based optical fibre sensors. The first kind involves the use of a tilted Bragg grating inscribed within the fibre core, prior to fibre coating, while the second relies on a surface relief grating photoinscribed after the fibre has been coated. Some of the devices operate in air with high coupling efficiency in excess of 40dB and an estimated index sensitivity of ??/?n = 90nm from 1 to 1.15 index range showing potential for gas sensing. Other sensors produced index sensitivities (??/?n) ranging from 6790nm to 12500nm in the aqueous index regime. The materials used for these fibre optical devices are germanium, silica, silver, gold and palladium.

Allsop, T.; Neal, R.; Kalli, K.; Davies, E. M.; Rehman, S.; Maier, R. R. J.; Barton, J.; Jones, J. D.; Webb, D. J.; Bennion, I.

2009-05-01

418

An Electrothermal Carbon Nanotube Gas Sensor  

Microsoft Academic Search

We show both gas pressure and species sensing capabilities based on the electrothermal effect of a multiwalled carbon nanotube (MWCNT). Upon exposure to gaseous environments, the resistance of a heated MWCNT is found to change following the conductive heat-transfer variances of gas molecules. To realize this mechanism, a suspended MWCNT is constructed by synthesis and assembly in localized chemical vapor

Takeshi Kawano; Heather C. Chiamori; Marcel Suter; Qin Zhou; Brian D. Sosnowchik; Liwei Lin

2007-01-01

419

High Temperature and High Sensitive NOx Gas Sensor with HeteroJunction Structure using Laser Ablation Method  

Microsoft Academic Search

In order to develop a high temperature (200°C˜400°C) and high sensitive NOx gas sensor, we developed a new structure of SiC-based hetero-junction device Pt\\/SnO2\\/SiC\\/Ni, Pt\\/In2O3\\/SiC\\/Ni and Pt\\/WO3\\/SiC\\/Ni using a laser ablation method for the preparation of both metal (Pt) electrode and metal-oxide film. It was found that Pt\\/In2O3\\/SiC\\/Ni sensor shows higher sensitivity to NO2 gas compared with the Pt\\/SnO2\\/SiC\\/Ni and

Wei Gao; Liqin Shi; Yuki Hasegawa; Teruaki Katsube

2006-01-01

420

High temperature and high sensitive NOx gas sensor with hetero-junction structure using laser ablation method  

Microsoft Academic Search

In order to develop a high temperature (200°C ? 400°C) and high sensitive NOx gas sensor, we developed a new structure of SiC-based hetero-junction device Pt\\/SnO2\\/SiC\\/Ni and Pt\\/WO3\\/SiC\\/Ni using a laser ablation method for the preparation of both metal (Pt) electrode and metal-oxide film. It was found that Pt\\/SnO2\\/SiC\\/Ni sensor show higher sensitivity to NO2 gas compared with the Pt\\/WO3\\/SiC\\/Ni

Wei Gaol; Liqin Shi; S. A. Khan; Y. Hasegawa; T. Katsube

2005-01-01

421

Field emission model of carbon nanotubes to simulate gas breakdown in ionization gas sensor  

NASA Astrophysics Data System (ADS)

A new field emission model of carbon nanotubes (CNTs) to simulate gas detection mechanism in CNT based ionization gas sensor has been developed. The new model consists of three modules which are combined together and embedded in the standard particle-in-cell/Monte Carlo collision codes. The functionality of the enhanced model is checked by varying the gas pressure and gap spacing in the simulations. From the results, around one order of magnitude decrease in the breakdown voltages and two orders of magnitude faster response time is observed. The lowest breakdown voltages are observed when intertube spacing is equal to height of the nanotube. The field enhancement factor ? is calculated from our model and compared with the ? of the well established model. The closeness among the values of ? validates the performance of our field emission model. Furthermore, the ? of our model is compared with the ? of the existing ionization gas sensors. It was found that the ? of our sensor is around 3 times better than the ? of the gold nanowire based ionization gas sensor and 28 times better than the ? of the other CNT based ionization gas sensor. These results suggest that by properly controlling the growth of CNT structures, an optimized CNT based ionization gas sensor can be realized.

Mahmood, Salman; Arif Burhanudin, Zainal; Salman, Aysha

2013-01-01

422

Carbon nanotube gas sensor conductance model, sensing mechanism analysis, and applications in flexible sensors and wireless sensors  

NASA Astrophysics Data System (ADS)

In this dissertation, the electrical property dependency of carbon nanotubes (CNTs) upon the humidity and chemical gas concentration is investigated. The electrical response of single-walled carbon nanotube (SWNT) networks to different humidity levels and gas molecules of ammonia (NH3) and nitrogen dioxide (NO2) at different concentrations was characterized by a sensor test system. In order to exclude the effect from contact resistance, the sheet resistance of SWNT networks was measured by transfer length method. The gas molecules concentration dependence of electrical property was analyzed, and two electrical models were proposed based on carrier transportation and adsorption isotherm respectively for different gas molecules. The electrical properties of SWNT networks estimated by the models were compared with the experimental data. The results show the models agree well with the experimental data. The primary objective of the sensor model is to understand the relationship between conductance of CNT networks and gas concentration. With this understanding, the model offers a precise measurement of the gas concentration based upon the electrical property of SWNT sensor. In addition, the mechanism of gas molecule adsorption on CNT networks is analyzed based on the conductance models. It is found that the conductance change of SWNT networks, induced by different humidity levels, is dominated by the thermal activation carrier hopping over the barriers between SWNTs. The average separation between the SWNTs increases linearly with the humidity levels. By contrast, when exposed to different NH3 and NO2, the conductance change is primarily determined by the charge transfer between gas molecules and CNTs. It shows that chemical molecules adsorption on the surface wall of SWNT causes the charge transfer. Furthermore, we investigated printed flexible electronics based on SWNTs and printable SWNT-based Frequency modulation (FM) passive wireless sensor tag on a flexible substrate with enhanced sensitivity. In this dissertation, we report a high sensitive flexible SWNT chemical gas sensor, capable of being easily fabricated. The sensor also shows good performance in linearity and flexibility. The flexible printed SWNT sensor with high sensitivity, low LOD and flexibility provides a promising solution to low-cost flexible sensor with high performance for mass production. Last, we developed a printable SWNT-based passive FM wireless sensor tag on a flexible substrate for ammonia detection. The FM wireless sensor tag shows an enhanced sensitivity and also exhibits a high linearity between the frequency shift and the logarithm of the chemical gas concentration. The linear response allows one to precisely predict the NH3 concentration by measuring the frequency shift of the FM wireless sensor tag. The experimental demonstration of the passive wireless sensor tag and accurate measurement of the NH3 concentration levels indicate that the FM modulated passive wireless sensor tag is promising for power-less standalone low-level NH3 sensing and monitoring.

Ling, Yunfeng

423

Gas Sensors Characterization and Multilayer Perceptron (MLP) Hardware Implementation for Gas Identification Using a Field Programmable Gate Array (FPGA)  

PubMed Central

This paper develops a primitive gas recognition system for discriminating between industrial gas species. The system under investigation consists of an array of eight micro-hotplate-based SnO2 thin film gas sensors with different selectivity patterns. The output signals are processed through a signal conditioning and analyzing system. These signals feed a decision-making classifier, which is obtained via a Field Programmable Gate Array (FPGA) with Very High-Speed Integrated Circuit Hardware Description Language. The classifier relies on a multilayer neural network based on a back propagation algorithm with one hidden layer of four neurons and eight neurons at the input and five neurons at the output. The neural network designed after implementation consists of twenty thousand gates. The achieved experimental results seem to show the effectiveness of the proposed classifier, which can discriminate between five industrial gases.

Benrekia, Faycal; Attari, Mokhtar; Bouhedda, Mounir

2013-01-01

424

Chemical Gas Sensors for Aerospace Applications  

NASA Technical Reports Server (NTRS)

Chemical sensors often need to be specifically designed (or tailored) to operate in a given environment. It is often the case that a chemical sensor that meets the needs of one application will not function adequately in another application. The more demanding the environment and specialized the requirement, the greater the need to adapt exiting sensor technologies to meet these requirements or, as necessary, develop new sensor technologies. Aerospace (aeronautic and space) applications are particularly challenging since often these applications have specifications which have not previously been the emphasis of commercial suppliers. Further, the chemical sensing needs of aerospace applications have changed over the years to reflect the changing emphasis of society. Three chemical sensing applications of particular interest to the National Aeronautics and Space Administration (NASA) which illustrate these trends are launch vehicle leak detection, emission monitoring, and fire detection. Each of these applications reflects efforts ongoing throughout NASA. As described in NASA's "Three Pillars for Success", a document which outlines NASA's long term response to achieve the nation's priorities in aerospace transportation, agency wide objectives include: improving safety and decreasing the cost of space travel, significantly decreasing the amount of emissions produced by aeronautic engines, and improving the safety of commercial airline travel. As will be discussed below, chemical sensing in leak detection, emission monitoring, and fire detection will help enable the agency to meet these objectives. Each application has vastly different problems associated with the measurement of chemical species. Nonetheless, the development of a common base technology can address the measurement needs of a number of applications.

Hunter, Gary W.; Liu, C. C.

1998-01-01

425

Solid-state electrochemical gas sensors  

Microsoft Academic Search

The solid-state electrochemical principle has been a selective and accurate way of sensing chemical components in various\\u000a environments, including liquid metal, for an extended period of time. Since after Carl Wagner’s interpretation of zirconia,\\u000a there appeared many advances in chemical sensor applications. The electrochemical techniques for the chemical measurements\\u000a have, in general, several major advantages compared to other methods. The

C. O. Park; J. W. Fergus; N. Miura; Jinsu Park; Angi Choi

2009-01-01

426

A novel CMOS temperature control system for resistive gas sensor arrays  

Microsoft Academic Search

A novel CMOS integrated system for the temperature control of resistive gas sensor interfaces is presented. It is formed by a sensor heater (which controls the sensor temperature), a resistance-to-frequency converter and digital control logic.

Giuseppe Ferri; Nicola Guerrini; Vincenzo Stornelli; Carlo Catalani

2005-01-01

427

Nanoporous metal oxides thin-films as "chemical reactive layers" for magnetoelastic sensors  

NASA Astrophysics Data System (ADS)

Freestanding magnetoelastic sensors are good candidates for in situ analysis of gases. After coating magnetoelastic ribbons with suitable nanoporous thin films, chemical reactive layers (CRL), sensitivity and specificity of the sensor for targeted gas increases. This thesis addresses two major aspects concerning magnetoelastic sensing of gases. The first aspect relates to developing methodology to measure mass of gas adsorbed from frequency shifts. Effective Young's modulus of the sensor coated with porous thin-films suffers large changes upon mass loading. This study demonstrates that changes in Young's modulus produced upon mass loading can be eliminated from the relationship between the magnitude of mass loaded and shifts in resonant frequency using the Two Different Length Sensors method. Sensitivity of the sensor not only depends on its properties but also depends on the nature of material being loaded and on its mass. Results show that sensitivity for the same sensor can range between 214 Hz/mg for mass loads of Au to 438,809 Hz/mg for acetone. The second aspect of this research deals with the development of CRL for ethylene sensing. Nanoporous metal oxides (TiO2 and SiO 2) surface modified with metals Pt(0) and metal ions Pt(II), Pd(II), Ag(I) were synthesized and evaluated as potential candidates. These materials were evaluated as ethylene adsorbents. We also studied the gain in weight upon ethylene adsorption and the nature of their chemical interaction with ethylene. Results from these studies showed that ethylene is completely mineralized (CO2+H2O) upon exposure to Pt(0)-modified TiO2 cermets. TiO2 modified with Pd(II) and Pt(II) oxidizes a fraction of ethylene to carboxylic and carboxylate species, causing adsorption of ethylene to be partially irreversible at room temperature. Ag(I)-doped materials react with ethylene to form surface complexes with sigma bonding character. Adsorption of ethylene is reversible process in this case. While the adsorption of ethylene by TiO2 is very small (0.02 mmols/g) at equilibrium with 40 ppmv in gas phase, the Pd(II), Pt(II) and Ag(I)-doped TiO2 adsorb, 0.50, 015 and 0.20 mmols/g respectively. The change in weight of materials upon exposure to ethylene is always less than 20% of that predicted by ethylene adsorption. This is due to desorption of water that takes place upon ethylene adsorption.

Zhang, Rong

428

Dry Process Based Infrared Sensors with CNT Film Absorber  

NASA Astrophysics Data System (ADS)

In this paper, we describe the fabrication and characterization of a front-side micromachined thermopiles consisting of a suspended membrane and a carbon nanotube (CNT) film absorber. Thermocouples of 52 pairs which are composed of phosphorous-doped silicon and aluminum were formed and connected in series. A CNT film collected by filter was transferred on hot junction. A CNT absorber has an absorptance of about 50% in the midinfrared region. The suspended membrane was fabricated by an isotropic silicon dry etching process with XeF2 gas at the front side of the substrates. The output voltage with the CNT film is found to be 250.2 mV at 7 mW of incident power, approximately 1.8 times higher than that of one without an absorber.

Yoo, Kum-Pyo; Hong, Hyun Pyo; Lim, Lee-Taek; Choi, Chang-Seon; Lee, Dong Il; Lee, Cheol Jin; Park, Chan-Won; Min, Nam Ki

429

Gas-detecting properties of surface acoustic wave ammonia sensors  

Microsoft Academic Search

The detecting properties of l-glutamic acid hydrochloride that is deposited on 128° YX-LiNbO3 surface acoustic wave (SAW) delay lines are studied in this work. SAW gas sensors that were based on l-glutamic acid hydrochloride had good sensitivity, selectivity, reversibility, and repeatability to ammonia gas. A detection limit of 0.56ppm for gaseous ammonia was observed when using l-glutamic acid hydrochloride for

Chi-Yen Shen; Chun-Pu Huang; Wang-Tsung Huang

2004-01-01

430

A wireless, passive carbon nanotube-based gas sensor  

Microsoft Academic Search

A gas sensor, comprised of a gas-responsive multiwall carbon nanotube (MWNT)-silicon dioxide (SiO2) composite layer deposited on a planar inductor-capacitor resonant circuit is presented here for the monitoring of carbon dioxide (CO2), oxygen (O 2), and ammonia (NH3). The absorption of different gases in the MWNT-SiO2 layer changes the permittivity and conductivity of the material and consequently alters the resonant

Keat Ghee Ong; Kefeng Zeng; Craig A. Grimes

2002-01-01

431

Low cost porous fiber optic multi-gas sensors for combustion control systems. Part 1: Fiber optic sensor feasibility analysis  

NASA Astrophysics Data System (ADS)

The objective was to develop an improved gas sensor system for accurate 'on-line' monitoring of combustion species aimed to improve the efficiency of gas fired combustion systems. Phase 1 of the program was the feasibility analysis of the proposed fiber optic multi-gas sensor. The analysis included: (1) a comprehensive literature search of research being performed in the areas of combustion diagnostics and fiber optic sensors; (2) a gas sensor vendor survey to evaluate the potential use of commercially available gas sensors for 'on-line' stack gas analysis; and (3) an optical fiber evaluation, including temperature testing of selected fiber samples and evaluation of fiber optic materials which are currently under development. Phase 2 of the program will entail fabrication and testing of the proof-of-concept fiber optic sensor system.

Schmidlin, E. M.

1991-05-01

432

Harmful gas recognition exploiting a CTL sensor array.  

PubMed

In this paper, a novel cataluminescence (CTL)-based sensor array consisting of nine types of catalytic materials is developed for the recognition of several harmful gases, namely carbon monoxide, acetone, chloroform and toluene. First, the experimental setup is constructed by using sensing nanomaterials, a heating plate, a pneumatic pump, a gas flow meter, a digital temperature device, a camera and a BPCL Ultra Weak Chemiluminescence Analyzer. Then, unique CTL patterns for the four types of harmful gas are obtained from the sensor array. The harmful gases are successful recognized by the PCA method. The optimal conditions are also investigated. Finally, experimental results show high sensitivity, long-term stability and good linearity of the sensor array, which combined with simplicity, make our system a promising application in this field. PMID:24113681

Wang, Qihui; Xie, Lijun; Zhu, Bo; Zheng, Yao; Cao, Shihua

2013-01-01

433

Harmful Gas Recognition Exploiting a CTL Sensor Array  

PubMed Central

In this paper, a novel cataluminescence (CTL)-based sensor array consisting of nine types of catalytic materials is developed for the recognition of several harmful gases, namely carbon monoxide, acetone, chloroform and toluene. First, the experimental setup is constructed by using sensing nanomaterials, a heating plate, a pneumatic pump, a gas flow meter, a digital temperature device, a camera and a BPCL Ultra Weak Chemiluminescence Analyzer. Then, unique CTL patterns for the four types of harmful gas are obtained from the sensor array. The harmful gases are successful recognized by the PCA method. The optimal conditions are also investigated. Finally, experimental results show high sensitivity, long-term stability and good linearity of the sensor array, which combined with simplicity, make our system a promising application in this field.

Wang, Qihui; Xie, Lijun; Zhu, Bo; Zheng, Yao; Cao, Shihua

2013-01-01

434

Chemical mechanical planarization characteristics of WO3 thin film for gas sensing  

NASA Astrophysics Data System (ADS)

It is important to control the microstructure and surface of films to use them in gas sensors. Chemical mechanical polishing (CMP) processing is one of the most useful methods for improving the surface roughness of films. The effects of CMP on the surface morphology of WO3 thin films prepared by the rf sputtering system were investigated in this article. The removal rate of the films increased, and the rms surface roughness decreased with the addition of an oxidizer to the tungsten slurry. Within-wafer nonuniformity was improved to below 5% when oxidizers of 5.0 and 2.5 vol %, respectively, were added to the tungsten slurry. The optimized oxidizer concentration, reflected by both the rms roughness values and a hillock-free surface with the good uniformity