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1

Carbon-palladium films as gas sensors (hydrogen, ammonia, methane)  

NASA Astrophysics Data System (ADS)

In this paper we present the results of the resistances changes of carbon-palladium films under the influences of gas like hydrogen, ammonia and methane. Our research has shown that carbon-palladium films (C-Pd films) according to the form and the structure in which they appear, they can respond to a variety of gases. The C-Pd film obtained by Physical Vapor Deposition (PVD) method is sensitive to hydrogen and do not respond to the ammonia. Thermal modification of the C-Pd film in Chemical Vapor Deposition (CVD) process affects the morphology of the film, increases its resistance and it causes that this film begins to react to the ammonia. This change causes that this film stops responding on hydrogen. Film sensitive to methane was obtained by changing the technology conditions of the PVD process. The reaction of C-Pd film on the hydrogen and the ammonia is increase resistance, while film sensitive to methane reacts by decrease of initial resistance value. In both cases, the changes are reversible after cleaning by air atmosphere. Different varieties of C-Pd films can be used to build selective sensors for hydrogen, ammonia and methane.

Rymarczyk, Joanna; Kami?ska, Anna; Krawczyk, S?awomir

2014-11-01

2

NiO thin-film formaldehyde gas sensor  

Microsoft Academic Search

The suitability of both pure and Li-doped NiO as a thin-film resistive gas sensor for formaldehyde has been investigated. Pure NiO had a linear formaldehyde sensitivity of 0.825mVppm?1 while that for 0.5at.% Li-doped NiO was 0.488mVppm?1 at 600°C. These gas-sensing materials also showed similar sensitivity for methanol and acetone as well as a reduced sensitivity for toluene and ethanol. Chloroform

James A. Dirksen; Kristin Duval; Terry A. Ring

2001-01-01

3

High sensitivity chlorine gas sensors using multicomponent transparent conducting oxide thin films  

Microsoft Academic Search

Newly developed semiconductor thin-film gas sensors with a high sensitivity for chlorine (Cl2) gas using multicomponent transparent conducting oxide (TCO) thin films such as MgO–In2O3, ZnO–In2O3 and Zn2In2O5–MgIn2O4 are described. The multicomponent oxide thin-film gas sensors used in this work exhibited an increase in resistance with exposure to Cl2 gas. The sensitivity of multicomponent TCO thin-film gas sensors could be

Toshihiro Miyata; Tomohiro Hikosaka; Tadatsugu Minami

2000-01-01

4

Gas sensor  

DOEpatents

A gas sensor is described which incorporates a sensor stack comprising a first film layer of a ferromagnetic material, a spacer layer, and a second film layer of the ferromagnetic material. The first film layer is fabricated so that it exhibits a dependence of its magnetic anisotropy direction on the presence of a gas, That is, the orientation of the easy axis of magnetization will flip from out-of-plane to in-plane when the gas to be detected is present in sufficient concentration. By monitoring the change in resistance of the sensor stack when the orientation of the first layer's magnetization changes, and correlating that change with temperature one can determine both the identity and relative concentration of the detected gas. In one embodiment the stack sensor comprises a top ferromagnetic layer two mono layers thick of cobalt deposited upon a spacer layer of ruthenium, which in turn has a second layer of cobalt disposed on its other side, this second cobalt layer in contact with a programmable heater chip.

Schmid, Andreas K.; Mascaraque, Arantzazu; Santos, Benito; de la Figuera, Juan

2014-09-09

5

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

6

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. PMID:22399977

Bakrania, Smitesh D.; Wooldridge, Margaret S.

2009-01-01

7

Nanostructured cobalt manganese ferrite thin films for gas sensor application  

Microsoft Academic Search

Ferrite compounds are very important because of their optical, electrical or magnetic properties. Moreover, many papers relate to their development as possible gas sensor.In this study, we were interested in using cobalt–manganese–ferrite as sensitive layer for CO2 sensor devices. Such an application required a high surface activity, and consequently a small crystallite size and a large surface area. The physical

Izabela Sandu; Lionel Presmanes; Pierre Alphonse; Philippe Tailhades

2006-01-01

8

Nanoparticle films made by gas phase synthesis: comparison of various techniques and sensor applications  

NASA Astrophysics Data System (ADS)

Nanoparticles can be generated by several different gas phase methods, such as gas deposition, laser-assisted chemical vapor deposition, and laser ablation. Some of the most important aspects - such as size-distribution, structure, and chemical composition of the generated nanoparticles (specifically W and WO3) - are presented and compared. WO3 nanoparticle films were deposited by an advanced gas deposition technique and were tested for sensor applications. Two different sensor devices were fabricated: Firstly, a thin Au-WO3 nanoparticle sandwich film was constructed, and conductance fluctuations of the Au film were measured as the sensor was exposed to alcohol vapor. Secondly, conductivity changes of a thick WO3 nanoparticle film were detected as it was exposed to test gases (H2S, NO2, and CO).

Heszler, Peter; Reyes, L. F.; Hoel, Anders; Landstrom, Lars; Lantto, V.; Granqvist, Claes-Goran

2003-07-01

9

Gas recognition by activated WO 3 thin-film sensors array  

Microsoft Academic Search

We have designed and fabricated a sensors array using WO3 thin films for gas analysis purposes. The sensing surface of the rf sputtered WO3 thin films has been differently activated by evaporated Pd, Au, Bi, Sb catalysts. The sensors have been characterized by d.c. electrical measurements for different gases such as H2S, SO2, CH4, NO, NO2 in a proper concentration

M. Penza; G. Cassano; F. Tortorella

2001-01-01

10

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

11

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

12

Fast Responsive Gas Sensor of Vertically Aligned Fluorine-Doped Tin Oxide Nanorod Thin Film  

NASA Astrophysics Data System (ADS)

We prepared fluorine-doped tin oxide (FTO) nanorod films and a conventional FTO thin film for the application of a semiconducting gas sensor by spray pyrolysis method. The lengths of FTO nanorods (FTON, 100 and 500 nm) were controlled by changing deposition times, and FTO thin film (FTOT) was also prepared as a reference. The gas sensitivity test shows FTON with long nanorods had higher sensitivity for both hydrogen and ethanol gases but slow response and recovery times, despite an advantage of the higher gas sensitivity. FTO nanorod film with short length about 100 nm showed relatively lower sensitivity, but fast gas response and recovery characteristics. The fast response and recovery for the analyte gases are attributed to the conductance of FTO nanorods, which is closely related to the diameter and length of nanorods.

Cho, Chan-Woo; Lee, Jong-Heun; Riu, Doh-Hyung; Kim, Chang-Yeoul

2012-04-01

13

Metal Oxide Nanowire and Thin-Film-Based Gas Sensors for Chemical Warfare Simulants Detection  

Microsoft Academic Search

This work concerns with metal oxide (MOX) gas sensors based on nanowires and thin films. We focus on chemical warfare agents (CWAs) detection to compare these materials from the functional point-of-view. We work with different chemicals including simulants for Sarin nerve agents, vescicant gases, cyanide agents, and analytes such as ethanol, acetone, ammonia, and carbon monoxide that can be produced

Andrea Ponzoni; Camilla Baratto; Sebastiano Bianchi; Elisabetta Comini; Matteo Ferroni; Matteo Pardo; Marco Vezzoli; Alberto Vomiero; Guido Faglia; Giorgio Sberveglieri

2008-01-01

14

Study of gas specificity in molybdenum trioxide/tungsten oxide thin film sensors and their arrays  

NASA Astrophysics Data System (ADS)

Chemical sensors that monitor gas concentrations through changes in the electrical resistance of their sensing elements are called resistive type detectors. Gas specificity is a highly desirable property in gas sensing, and is defined as the preferred response to a particular gas in the presence of other interfering compounds. The lack of specificity and limited selectivity of existing chemosensors often results in false alarms, thus reducing the reliability of these devices. This work focuses on specific gas-oxide interactions in transition metal oxides that exhibit structure sensitivity in catalytic processes. The hypothesis is that gas specificity depends on the oxide's polymorph phase used in sensing. MoO3 and WO3 thin films have been chosen for this study as the model gas sensing elements. Ammonia, nitrogen oxides and hydrocarbons are the target gases selected. Gas sensing films were fabricated using ion beam deposition and sol-gel techniques. The effects of processing parameters, film thickness, stabilization heat treatment, and sensing temperature on the films' microstructures have been studied. The microstructures of the films are characterized using transmission electron microscopy, X-ray diffraction, and scanning electron microscopy. Differential scanning calorimetry experiments are performed to establish the phase stability fields for the various polymorphs of the model systems under study. Gas sensing tests were carried out using the orthorhombic and monoclinic phases of MoO3 and WO3. It was found that it is possible to control the microstructure and operating temperature of a single semiconducting metal oxide film (viz, MoO3 or WO3) so as to produce polymorphs that are sensitive to a particular gas. A suitable sensor array is proposed consisting of un-doped metal oxide which can detect different target gas species selectively.

Prasad, Arun Kapaleeswaran

15

Kinetic behavior analysis of porphyrin Langmuir-Blodgett films for conductive gas sensors  

NASA Astrophysics Data System (ADS)

Meso, meso'-buta-1,3-diyne-bridged Ni (II) octaethylporphyrin dimer thin films have been deposited by the Langmuir-Blodgett method and, for the first time, have been considered as the active layer in resistive gas sensors. In particular, the electrical conductivities of these films undergo a remarkable variation due to exposure to small concentrations of NO in air at an operating temperature of 50 °C. To interpret the behavior of such organic films, a model has been built up and the conductivity variation as a function of test gas concentrations and time has been derived. The fitting of theoretical and experimental behavior allows us to determine the number of adsorbed gas molecules per porphyrin dimer, response and recovery times, adsorption and desorption coefficients. The reliability of the model is proved by obtained results. In particular, the determined adsorption and desorption coefficients depend only on test gas species but are unaffected by other experimental conditions such as gas concentration.

Tepore, A.; Serra, A.; Manno, D.; Valli, L.; Micocci, G.; Arnold, D. P.

1998-08-01

16

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. PMID:22164007

Chaisitsak, Sutichai

2011-01-01

17

Aqueous ozone detector using In 2O 3 thin-film semiconductor gas sensor  

Microsoft Academic Search

A detector for continuous determination of a trace amount of aqueous ozone, utilizing an ozone-extraction process from liquid (water) into the gas phase and an In2O3 thin-film semiconductor ozone gas sensor, has been developed. It has many advantages, including high sensitivity to aqueous ozone and high aqueous ozone selectivity in the presence of various kinds of interfering compounds in water.

Tadashi Takada; Hiromasa Tanjou; Tatsuo Saito; Kenji Harada

1995-01-01

18

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

19

Performance and Stress Analysis of Metal Oxide Films for CMOS-Integrated Gas Sensors.  

PubMed

The integration of gas sensor components into smart phones, tablets and wrist watches will revolutionize the environmental health and safety industry by providing individuals the ability to detect harmful chemicals and pollutants in the environment using always-on hand-held or wearable devices. Metal oxide gas sensors rely on changes in their electrical conductance due to the interaction of the oxide with a surrounding gas. These sensors have been extensively studied in the hopes that they will provide full gas sensing functionality with CMOS integrability. The performance of several metal oxide materials, such as tin oxide (SnO2), zinc oxide (ZnO), indium oxide (In2O3) and indium-tin-oxide (ITO), are studied for the detection of various harmful or toxic cases. Due to the need for these films to be heated to temperatures between 250°C and 550°C during operation in order to increase their sensing functionality, a considerable degradation of the film can result. The stress generation during thin film deposition and the thermo-mechanical stress that arises during post-deposition cooling is analyzed through simulations. A tin oxide thin film is deposited using the efficient and economical spray pyrolysis technique, which involves three steps: the atomization of the precursor solution, the transport of the aerosol droplets towards the wafer and the decomposition of the precursor at or near the substrate resulting in film growth. The details of this technique and a simulation methodology are presented. The dependence of the deposition technique on the sensor performance is also discussed. PMID:25815445

Filipovic, Lado; Selberherr, Siegfried

2015-01-01

20

Room-temperature semiconductor gas sensor based on nonstoichiometric tungsten oxide nanorod film  

NASA Astrophysics Data System (ADS)

Porous tungsten oxide films were deposited onto a sensor substrate with a Si bulk-micromachined hotplate, by drop-coating isopropyl alcohol solution of highly crystalline tungsten oxide (WO2.72) nanorods with average 75nm length and 4nm diameter. The temperature-dependent gas sensing characteristics of the films have been investigated over the mild temperature range from 20to250°C. While the sensing responses for ammonia vapor showed increase in electrical conductivity at temperatures above 150°C as expected for n-type metal oxide sensors, they exhibited the opposite behavior of unusual conductivity decrease below 100°C. Superb sensing ability of the sensors at room temperature in conjunction with their anomalous conductivity behavior might be attributed to unique nanostructural features of very thin, nonstoichiometric WO2.72.

Kim, Yong Shin; Ha, Seung-Chul; Kim, Kyuwon; Yang, Haesik; Choi, Sung-Yool; Kim, Youn Tae; Park, Joon T.; Lee, Chang Hoon; Choi, Jiyoung; Paek, Jungsun; Lee, Kwangyeol

2005-05-01

21

Transparent conducting films of hierarchically nanostructured polyaniline networks on flexible substrates for high-performance gas sensors.  

PubMed

Transparent chemical gas sensors are assembled from a transparent conducting film of hierarchically nanostructured polyaniline (PANI) networks fabricated on a flexible PET substrate, by coating silver nanowires (Ag NWs) followed by the in situ polymerization of aniline near the sacrificial Ag NW template. The sensor exhibits enhanced gas sensing performance at room temperature in both sensitivity and selectivity to NH3 compared to pure PANI film. PMID:25164185

Bai, Shouli; Sun, Chaozheng; Wan, Pengbo; Wang, Cheng; Luo, Ruixian; Li, Yaping; Liu, Junfeng; Sun, Xiaoming

2015-01-21

22

A micromachined gas chromatographic column to optimize the gas selectivity for a resistive thin film gas sensor  

Microsoft Academic Search

Indoor air quality monitoring applications require both high selectivity and sensitivity, which are difficult to reach with solid state gas sensors. An ultra small packed gas chromatographic column designed for a micro total analyzing system (?TAS) based on a solid state gas sensor as a detector and used to determine the concentration of benzene, toluene and xylene (BTX) in indoor

Jorg Sturmann; W. Benecke; S. Zampolli; I. Elmi; G. C. Cardinali; W. Lang

2005-01-01

23

Surface and morphological studies of pure and Sb doped thin film gas sensors  

NASA Astrophysics Data System (ADS)

n-type transparent conducting 10% Antimony-doped Tin Oxide (ATO) films were fabricated on glass substrates by spray pyrolysis for CO sensing applications. Antimony tri chloride (SbCl3) was added to stannous chloride solution to prepare the antimony doped Tin Oxide (ATO) films. The samples were deposited at temperatures between 350°-400°C following which they were sintered at 450°C for 2 hours. The structural and morphological properties of the films were studied using XRD, SEM, HRTEM, and AFM. HRTEM micrographs of doped ATO films revealed grains of size around 5 nm, and the lattice lines (planes) are clearly seen in some of the grains. The gas sensor response was temperature dependent displaying its highest responsivity at 400°C.

Gupta, Archana; Rajaram, P.; Bhatnagar, M. C.

2013-02-01

24

Optical CO gas sensor using a cobalt oxide thin film prepared by pulsed laser deposition under various argon pressures.  

PubMed

An optical CO gas sensor was investigated using cobalt oxide thin films prepared by pulsed laser deposition. The cobalt oxide films were deposited on quartz glass and silicon wafer substrates in Ar at 0.07-133 Pa. The morphology and crystal phase of the films were changed by Ar pressure. Sensitivity was estimated as the transmittance change of the film in dry air and at 200 ppm of CO gas ambient at 350 degrees C. The morphology of the films greatly affected the sensing properties. The optimum Ar pressure for cobalt oxide film preparation for CO gas sensing was suggested to be 13.3 Pa, based on the relationship between the morphology and the optical sensor properties of the films. PMID:17107147

Nam, Hyun-Jeong; Sasaki, Takeshi; Koshizaki, Naoto

2006-11-23

25

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. PMID:22574039

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

2009-01-01

26

Hydrogen gas sensors using a thin Ta2O5 dielectric film  

NASA Astrophysics Data System (ADS)

A capacitive-type hydrogen gas sensor with a MIS (metal-insulator-semiconductor) structure was investigated for high-temperature applications. In this work, a tantalum oxide (Ta2O5) layer of tens of nanometers in thickness formed by oxidizing tantalum film in rapid thermal processing (RTP) was exploited with the purpose of sensitivity improvement. Silicon carbide (SiC), which is good even at high temperatures over 500 °C, was used as the substrate. We fabricated sensors composed of Pd/Ta2O5/SiC, and the dependences of the capacitance response properties and the I-V characteristics on the hydrogen concentration were analyzed from the temperature range of room temperature to 500 °C. As a result, our hydrogen sensor showed promising performance with respect to the sensitivity and the adaptability at high temperature.

Kim, Seongjeen

2014-12-01

27

Sensing properties to dilute chlorine gas of indium oxide based thin film sensors prepared by electron beam evaporation  

Microsoft Academic Search

Indium oxide based thin film sensors have been prepared by means of an electron beam evaporation and subjected to the detection of dilute Cl2 gas less than ppm-level. Among various In2O3 based sensors tested, the In2O3 thin film modified with Fe2O3 (1wt.%) showed extremely high sensitivity to dilute Cl2 gas of 0.2–5ppm. The Fe2O3–In2O3 sensor showed the sensitivity as high

Jun Tamaki; Chizuko Naruo; Yoshifumi Yamamoto; Masao Matsuoka

2002-01-01

28

Characterization of a thin film tin oxide gas sensor deposited by chemical spray  

NASA Astrophysics Data System (ADS)

SnO2 thin films have been used to fabricate a semiconductor gas sensor device, mainly for CO. We report the deposition conditions, characterization of the films and the devices. The thin films were deposited on glass and corning 7059 substrates by chemical spray technique from a starting solution containing SnCl4:5H2O diluted in ethyl alcohol at several molar concentrations. The substrate temperatures were kept at 300 and 350 °C for different flux rates of the solution. We used as electrical contacts either conductive silver firing or vacuum evaporated silver. The electrical characterization was made in a constant gas flux containing different CO concentrations, as a function of sensor temperature. The devices show a high sensitivity (about 1 order of magnitude at low concentrations, 100 ppm and 300 °C). They show also a high stability. Finally we discuss the effect of the thickness on the sensitivity of the devices and we show that it is necessary to control the thickness accurately in order to have good quality and reproducible results.

Olvera, M. de la L.; Maldonado, A.; Asomoza, R.

1996-07-01

29

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

30

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

31

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); Hoffheins, Barbara S. (Knoxville, TN); Fleming, Pamela H. (Oak Ridge, TN)

1994-01-01

32

Fabrication of NOx gas sensors using In2O3ZnO composite thin Films  

Microsoft Academic Search

In2O3-ZnO composite thin films were fabricated and their NOx sensing characteristics were investigated in this study. The content of ZnO in In2O3-ZnO thin film was controlled by adjusting the Zn2+\\/In3+ molar ratio (r) during the film preparation. The results showed that the incorporation of ZnO into the In2O3 thin film can greatly improve the sensor reponse to NOx at operation

Chia-Yu Lin; Yueh-Yuan Fang; Chii-Wann Lin; Craig A. Jeffrey; James J. Tunney; Kuo-Chuan Ho

2009-01-01

33

Fabrication of iron titanium oxide thin film and its application as opto-electronic humidity and liquefied petroleum gas sensors  

NASA Astrophysics Data System (ADS)

Present paper explores the synthesis, characterization, and opto-electronic humidity as well as liquefied petroleum gas (LPG) sensing applications of iron titanium oxide nanocomposite. Thin film of iron titanium oxide was deposited on an equilateral borosilicate glass prism using sol-gel spin coating process. X-ray diffraction reveals the formation of iron titanium oxide having minimum crystallite size 9 nm. The opto-electronic humidity sensing properties of the fabricated film were investigated at different angles of incidence of the light. It was observed that the intensity of reflected light increased with an increase in relative humidity (%RH) in the range 5-95. The fabricated film shows maximum sensitivity 4.5 ?W/%RH, which is quite significant for sensor fabrication purposes. The maximum percentage sensor response for LPG was found 2600 which is many folds more than the earlier reported titania based LPG sensor.

Verma, Nidhi; Singh, Satyendra; Srivastava, Richa; Yadav, B. C.

2014-04-01

34

A new room temperature gas sensor based on pigment-sensitized TiO2 thin film for amines determination.  

PubMed

A new room temperature gas sensor was fabricated with pigment-sensitized TiO2 thin film as the sensing layer. Four natural pigments were extracted from spinach (Spinacia oleracea), red radish (Raphanus sativus L), winter jasmine (Jasminum nudiflorum), and black rice (Oryza sativa L. indica) by ethanol. Natural pigment-sensitized TiO2 sensor was prepared by immersing porous TiO2 films in an ethanol solution containing a natural pigment for 24h. The hybrid organic-inorganic formed films here were firstly exposed to atmospheres containing methylamine vapours with concentrations over the range 2-10 ppm at room temperature. The films sensitized by the pigments from black-rice showed an excellent gas-sensitivity to methylamine among the four natural pigments sensitized films due to the anthocyanins. The relative change resistance, S, of the films increased almost linearly with increasing concentrations of methylamine (r=0.931). At last, the black rice pigment sensitized TiO2 thin film was used to determine the biogenic amines generated by pork during storage. The developed films had good sensitivity to analogous gases such as putrscine, and cadaverine that will increase during storage. PMID:24934102

Yanxiao, Li; Xiao-bo, Zou; Xiao-wei, Huang; Ji-yong, Shi; Jie-wen, Zhao; Holmes, Mel; Hao, Limin

2015-05-15

35

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

36

SnO2/Pt Thin Film Laser Ablated Gas Sensor Array  

PubMed Central

A gas sensor array was developed in a 10 × 10 mm2 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 SnO2 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 O2. 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

37

High sensitive formaldehyde graphene gas sensor modified by atomic layer deposition zinc oxide films  

SciTech Connect

Zinc oxide (ZnO) thin films with various thicknesses were fabricated by Atomic Layer Deposition on Chemical Vapor Deposition grown graphene films and their response to formaldehyde has been investigated. It was found that 0.5?nm ZnO films modified graphene sensors showed high response to formaldehyde with the resistance change up to 52% at the concentration of 9 parts-per-million (ppm) at room temperature. Meanwhile, the detection limit could reach 180 parts-per-billion (ppb) and fast response of 36?s was also obtained. The high sensitivity could be attributed to the combining effect from the highly reactive, top mounted ZnO thin films, and high conductive graphene base network. The dependence of ZnO films surface morphology and its sensitivity on the ZnO films thickness was also investigated.

Mu, Haichuan; Zhang, Zhiqiang; Wang, Keke; Xie, Haifen, E-mail: hfxie@ecust.edu.cn [Department of Physics, School of Science, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Zhao, Xiaojing; Liu, Feng [Department of Physics, Shanghai Normal University, 100 Guilin Road, Shanghai 200234 (China)

2014-07-21

38

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

39

Crown-ether lutetium bisphthalocyanine Langmuir-Blodgett films as gas sensors  

Microsoft Academic Search

The gas adsorption and electrochromic properties of Langmuir-Blodgett films of octa-(15-crown-5)-lutetium bisphthalocyanine (CR?Pc2Lu) are reported. Films of CR?Pc2Lu were sensitive to electron donor and electron acceptor gases as well as tobacco smoke. The adsorption was traced using electronic adsorption spectroscopy. The presence of crown ether groups on the phthalocyanine ring increased the sensitivity of the films to oxidizing gases. Stable

M. L. Rodríguez-Méndez; J. Souto; J. de Saja-González; J. A. de Saja

1996-01-01

40

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

41

Qualitative and quantitative differentiation of gases using ZnO thin film gas sensors and pattern recognition analysis.  

PubMed

In the present work we have grown highly textured, ultra-thin, nano-crystalline zinc oxide thin films using a metal organic chemical vapor deposition technique and addressed their selectivity towards hydrogen, carbon dioxide and methane gas sensing. Structural and microstructural characteristics of the synthesized films were investigated utilizing X-ray diffraction and electron microscopy techniques respectively. Using a dynamic flow gas sensing measurement set up, the sensing characteristics of these films were investigated as a function of gas concentration (10-1660 ppm) and operating temperature (250-380 °C). ZnO thin film sensing elements were found to be sensitive to all of these gases. Thus at a sensor operating temperature of ~300 °C, the response% of the ZnO thin films were ~68, 59, and 52% for hydrogen, carbon monoxide and methane gases respectively. The data matrices extracted from first Fourier transform analyses (FFT) of the conductance transients were used as input parameters in a linear unsupervised principal component analysis (PCA) pattern recognition technique. We have demonstrated that FFT combined with PCA is an excellent tool for the differentiation of these reducing gases. PMID:24551870

Pati, Sumati; Maity, A; Banerji, P; Majumder, S B

2014-04-01

42

Tungsten trioxide (WO 3) sputtered thin films for a NO x gas sensor  

Microsoft Academic Search

WO3 thin films have been deposited by reactive rf sputtering onto low-cost glass substrates as gas sensitive coatings. The properties of the grown films have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) in order to characterize their structure, composition, surface chemistry. The d.c. electrical response to different gases of the WO3 thin

M Penza; M. A Tagliente; L Mirenghi; C Gerardi; C Martucci; G Cassano

1998-01-01

43

Nanonails structured ferric oxide thick film as room temperature liquefied petroleum gas (LPG) sensor  

NASA Astrophysics Data System (ADS)

In the present work, ferric oxide nanonails were prepared by screen printing method on borosilicate glass substrate and their electrical and LPG sensing properties were investigated. The structural and morphological characterizations of the material were analyzed by means of X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD pattern revealed crystalline ?-phase and rhombohedral crystal structure. SEM images show nanonails type of morphology throughout the surface. Optical characterization of the film was carried out by UV-visible spectrophotometer. By Tauc plot the estimated value of band gap of film was found 3.85 eV. The LPG sensing properties of the ferric oxide film were investigated at room temperature for different vol.% of LPG. The variations in electrical resistance of the film were measured with the exposure of LPG as a function of time. The maximum values of sensitivity and sensor response factors were found 51 and 50 respectively for 2 vol.% of LPG. The activation energy calculated from Arrhenius plot was found 0.95 eV. The response and recovery time of sensing film were found ˜120 s and 150 s respectively. These experimental results show that nanonails structured ferric oxide is a promising material as LPG sensor.

Yadav, B. C.; Singh, Satyendra; Yadav, Anuradha

2011-01-01

44

Plasmonic nanocomposite thin film enabled fiber optic sensors for simultaneous gas and temperature sensing at extreme temperatures  

NASA Astrophysics Data System (ADS)

Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by integration of Au-nanoparticle based plasmonic nanocomposite thin films with optical fibers in an evanescent wave absorption spectroscopy configuration. Such sensors can potentially enable simultaneous temperature and gas sensing at temperatures approaching 900-1000 °C in a manner compatible with embedded and distributed sensing approaches. The approach is demonstrated using the Au/SiO2 system deposited on silica-based optical fibers. Stability of optical fibers under relevant high temperature conditions and interactions with changing ambient gas atmospheres is an area requiring additional investigation and development but the simplicity of the sensor design makes it potentially cost-effective and may offer a potential for widespread deployment.Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by integration of Au-nanoparticle based plasmonic nanocomposite thin films with optical fibers in an evanescent wave absorption spectroscopy configuration. Such sensors can potentially enable simultaneous temperature and gas sensing at temperatures approaching 900-1000 °C in a manner compatible with embedded and distributed sensing approaches. The approach is demonstrated using the Au/SiO2 system deposited on silica-based optical fibers. Stability of optical fibers under relevant high temperature conditions and interactions with changing ambient gas atmospheres is an area requiring additional investigation and development but the simplicity of the sensor design makes it potentially cost-effective and may offer a potential for widespread deployment. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02891g

Ohodnicki, Paul R.; Buric, Michael P.; Brown, Thomas D.; Matranga, Christopher; Wang, Congjun; Baltrus, John; Andio, Mark

2013-09-01

45

Toxic gas sensors using thin film transistor platform at low temperature  

E-print Network

Semiconducting metal-oxides such as SnO?, TiO?, ZnO and WO? are commonly used for gas sensing in the form of thin film resistors (TFRs) given their high sensitivity to many vapor species, simple construction and capability ...

Jin, Yoonsil

2009-01-01

46

Kinetic characteristics of SnO2 thin-film gas sensors for environmental monitoring  

NASA Astrophysics Data System (ADS)

In this report we presented results of gas sensitivity' kinetics analysis for undoped SnO2 thin films, deposited by spray pyrolysis method, using SnCl4x5H2O alcohol solution. The comparison of gas sensitivity's kinetics in measurement cycles air yields {air+(0.08 - 1.7%)CO} yields air and air yields (N2 + 0.5%O2} yields air for different thickness of SnO2 films (d equals 40 - 200 nm) and operating temperature (T equals 150 - 400 degree(s)C) was carried out. We have determined the kinetic parameters ((tau) and Eact) and made a conclusion that kinetics of gas sensitivity is limited by the rate of SnO2 surface refilling by oxygen.

Korotchenkov, Ghennadii S.; Brynzari, Vladimir I.; Dmitriev, Sergei V.

1998-12-01

47

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

48

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

49

A micromachined thin-film gas flow sensor for microchemical reactors  

NASA Astrophysics Data System (ADS)

As microchemical systems (MCS) have gained in importance since their introduction in the last decade, it has become recognized that appropriate sensing and control capabilities are needed if MCS are to reach their potential. In this context, we present a study of the working behavior of a novel thin-film micro flow sensor which is integrated with a silicon microreactor with a submillimeter channel. A simple-to-fabricate device based on the concept of calorimetric sensing was chosen as a model structure to understand the important factors controlling sensor performance. Various design options for the sensor were explored by the use of computational fluid dynamics simulations. We found that sensitivity depends strongly on certain design factors. In summary, sensitivity is improved with (a) higher values of the resistors that detect flow-induced temperature changes, (b) shorter distances between the resistor that provides a source of heat and the thermally sensitive resistors and (c) higher input power to the heating resistor. Item (a) was found to have by far the strongest effect of the three. Reproducibility tests were conducted and the sensor exhibited consistent performance throughout the entire test range of 0-20 sccm which is an appropriate fit to the flow capacity of the microchannel. Finally, response time was assessed by simulating the transient behavior of the sensor with a thermal capacitance model, which yielded an accurate prediction of the experimental response of the device. The response time is approximately 70 ms at a typical flow rate of 10 sccm. According to the understanding gained from the model, the sensor response time can be improved by reducing the substrate thickness, using a lower density substrate material, and increasing the convective heat transfer coefficient in the channel.

Shin, W. C.; Besser, R. S.

2006-04-01

50

Plasmonic nanocomposite thin film enabled fiber optic sensors for simultaneous gas and temperature sensing at extreme temperatures.  

PubMed

Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by integration of Au-nanoparticle based plasmonic nanocomposite thin films with optical fibers in an evanescent wave absorption spectroscopy configuration. Such sensors can potentially enable simultaneous temperature and gas sensing at temperatures approaching 900-1000 °C in a manner compatible with embedded and distributed sensing approaches. The approach is demonstrated using the Au/SiO2 system deposited on silica-based optical fibers. Stability of optical fibers under relevant high temperature conditions and interactions with changing ambient gas atmospheres is an area requiring additional investigation and development but the simplicity of the sensor design makes it potentially cost-effective and may offer a potential for widespread deployment. PMID:23948985

Ohodnicki, Paul R; Buric, Michael P; Brown, Thomas D; Matranga, Christopher; Wang, Congjun; Baltrus, John; Andio, Mark

2013-10-01

51

Using a TiO 2\\/ZnO double-layer film for improving the sensing performance of ZnO based NO gas sensor  

Microsoft Academic Search

NO gas sensors, based on ZnO thin film (ZnOfilm), TiO2 nanoparticulate film (TiO2NP), and TiO2NP\\/ZnOfilm double-layer film, were fabricated, and their sensing characteristics towards NO gas were investigated in this study. The maximal response of a ZnOfilm deposited onto a rougher Al2O3 substrate, towards NO gas, was higher than that of a ZnOfilm deposited on a smoother glass substrate. Although

Chia-Yu Lin; Jiang-Ging Chen; Wei-Yi Feng; Chii-Wann Lin; Ju-Wen Huang; James J. Tunney; Kuo-Chuan Ho

2011-01-01

52

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

53

Semiconductor gas sensors based on nanostructured tungsten oxide  

Microsoft Academic Search

Semiconductor gas sensors based on nanocrystallline WO3 films were produced by two different methods. Advanced reactive gas evaporation was used in both cases either for a direct deposition of films (deposited films) or to produce ultra fine WO3 powder which was used for screen printing of thick films. The deposited films sintered at 480 °C and the screen-printed films sintered

J. L Solis; S Saukko; L Kish; C. G Granqvist; V Lantto

2001-01-01

54

The Evolution of High Temperature Gas Sensors.  

SciTech Connect

Gas sensor technology based on high temperature solid electrolytes is maturing rapidly. Recent advances in metal oxide catalysis and thin film materials science has enabled the design of new electrochemical sensors. We have demonstrated prototype amperometric oxygen sensors, nernstian potentiometric oxygen sensors that operate in high sulfur environments, and hydrocarbon and carbon monoxide sensing mixed potentials sensors. Many of these devices exhibit part per million sensitivities, response times on the order of seconds and excellent long-term stability.

Garzon, F. H. (Fernando H.); Brosha, E. L. (Eric L.); Mukundan, R. (Rangachary)

2001-01-01

55

Sol-gel TiO2 films as NO2 gas sensors  

NASA Astrophysics Data System (ADS)

TiO2 films were prepared by a sol-gel technique with commercial TiO2 powder as a source material (P25 Degussa AG). After a special treatment, printing paste was prepared. The TiO2 layers were formed by means of drop-coating on Si-control wafers and on the Au-electrodes of quartz resonators. The surface morphology of the films was examined by scanning electron microscopy (SEM). Their structure was studied by Raman spectroscopy and the surface composition was determined by X-ray photoelectron spectroscopy (XPS). The layers had a grain-like surface morphology and consisted mainly of anatase TiO2 phase. The sensitivity of the TiO2 films to NO2 was assessed by the quartz crystal microbalance (QCM) technique. To this end, the films were deposited on both sides of a 16-MHz QCM. The sensing characteristic of the TiO2-QCM structure was investigated by measuring the resonant frequency shift (?F) of the QCM due to the mass loading caused by NO2 adsorption. The Sauerbrey equation was applied to establish the correlation between the QCM frequency changes measured after exposure to different NO2 concentrations and the mass-loading of the QCM. The experiments were carried out in a dynamic mode on a special laboratory setup with complete control of the process parameters. The TiO2 films were tested in the NO2 concentration interval from 10 ppm to 5000 ppm. It was found that a TiO2 loading of the QCM by 5.76 kHz corresponded to a system sensitive to NO2 concentrations above 250 ppm. On the basis of the frequency-time characteristics (FTCs) measured, AF at different NO2 concentrations was defined, the adsorption/desorption cycles were studied and the response and recovery times were estimated. The results obtained show that the process is reversible in the NO2 interval investigated. The results further suggested that TiO2 films prepared by a sol-gel method on a QCM can be used as a sensor element for NO2 detection.

Georgieva, V.; Gadjanova, V.; Grechnikov, A.; Donkov, N.; Sendova-Vassileva, M.; Stefanov, P.; Kirilov, R.

2014-05-01

56

Thin-film temperature sensors for gas turbine engines Problems and prospects  

NASA Technical Reports Server (NTRS)

The erosion and corrosion of thermocouples used to measure the temperature in turbine engines are studied. Structural and metallurgical interactions and instabilities at thermocouple interfaces are analyzed. Consideration is given to the adhesion, dielectric quality, surface topography, and hardness of the thermal oxides; it is observed that the structural and thermoelectric stability of thin-film thermocouple elements depends on adhesion, surface topography, and dielectric strength. The electrical conductivity and impurity content of the oxide scale are evaluated. Methods for improving the adhesion of thermocouples on the alumina surfaces are described. Compositional inhomogeneities in the sensors and contamination of the thermocouple elements are examined. The fabrication of the thermocouples is discussed. It is noted that Al2O3 and Si3N4 are useful for developing stable thermocouple elements on the surface of the blades and vanes.

Budhani, R. C.; Prakash, S.; Bunshah, R. F.

1986-01-01

57

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

58

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

59

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. PMID:22291561

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

2009-01-01

60

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

61

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

62

Indium tin oxide (ITO) thin film gas sensor for detection of methanol at room temperature  

Microsoft Academic Search

Thin films of indium tin oxide (In2O3+SnO2) (ITO) were grown on alumina substrate using the direct evaporation method. The sensing characteristics of these films to methanol vapors were studied at room temperature. The effects of different concentrations of tin oxide in indium oxide and film thickness on sensitivity were studied. The effects of thin layers of noble metals—Au, Ag, Pt

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

2003-01-01

63

Sol-Gel derived Sb-doped SnO II/SiO II nano-composite thin films for gas sensors  

NASA Astrophysics Data System (ADS)

Sb-doped SnO II/SiO II nano-composite thin films prepared by sol-gel dip-coating method have been studied. By using X-ray diffraction (XRD), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy, detailed investigation on the structure and morphology of the films has shown the crystalline grain size of Sb-doped SnO II/SiO II thin films is about 34nm, with larger specific surface area and duty porosity, which is fit for gas-sensing materials. The adulteration of SiO II particles leads to the condensation of Sn-OH and the strengthening of gel network, and improve the adhesion of the films. In addition, the optical properties of the thin films were studied by UV-Vis spectra and p-polarized light reflectance angular spectrum. The results showthat the optical transmissivity of Sb-doped SnO II/SiO II thin films is higher, near 95% in visible spectrum range, the measured optical gap is found equal to 3.67eV, also the films take on smaller refractive index and extinction coefficient compared with those of the SnO II and Sb:SnO II films, which is compatible with the semiconductor substrate in the solar cell. Further, the gas-sensing test was made to three kinds of gas C 3H 8, C IIH 5OH and NH 3 in our novel high sensitive scheme for optical film sensors. The results indicate that Sb doping to SnO II films greatly improves the gas sensitivity to C IIH 5OH, and the gas sensitivity of Sb:SnO II/SiO II nano-composite thin films are higher than that of Sb:SnO II thin films. The detection sensitivity of this optical film sensor is available to 10 -1ppm provided that the resolution of reflectance ratio is 10 -2.

Gu, Zhengtian; Liang, Peihui; Zhang, Weiqing

2006-05-01

64

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

65

Fabrication and its characteristics of metal-loaded TiO 2\\/SnO 2 thick-film gas sensor for detecting dichloromethane  

Microsoft Academic Search

This study investigated sensitivity of the gas sensor to chemical warfare agents with the various operating temperatures and catalysts. The nano-sized SnO2 powder mixed with metal oxide (TiO2) was doped with transition metals (Pt, Pd and In). Thick film of nano-sized SnO2 powder and TiO2 was prepared by screen-printing method onto Al2O3 substrates with platinum electrode and chemical precipitation method.

Young Ho Park; Hye-Kyung Song; Chang-Seop Lee; Jong-Gi Jee

2008-01-01

66

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

67

Fabrication of SnO2-Reduced Graphite Oxide Monolayer-Ordered Porous Film Gas Sensor with Tunable Sensitivity through Ultra-Violet Light Irradiation.  

PubMed

A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties. PMID:25758292

Xu, Shipu; Sun, Fengqiang; Yang, Shumin; Pan, Zizhao; Long, Jinfeng; Gu, Fenglong

2015-01-01

68

Fabrication of SnO2-Reduced Graphite Oxide Monolayer-Ordered Porous Film Gas Sensor with Tunable Sensitivity through Ultra-Violet Light Irradiation  

PubMed Central

A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties. PMID:25758292

Xu, Shipu; Sun, Fengqiang; Yang, Shumin; Pan, Zizhao; Long, Jinfeng; Gu, Fenglong

2015-01-01

69

Fabrication of SnO2-Reduced Graphite Oxide Monolayer-Ordered Porous Film Gas Sensor with Tunable Sensitivity through Ultra-Violet Light Irradiation  

NASA Astrophysics Data System (ADS)

A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties.

Xu, Shipu; Sun, Fengqiang; Yang, Shumin; Pan, Zizhao; Long, Jinfeng; Gu, Fenglong

2015-03-01

70

An optical gas sensor based on polyaniline Langmuir-Blodgett films  

Microsoft Academic Search

The technique of surface plasmon resonance has been used to characterize Langmuir-Blodgett films of polyaniline. The thickness per layer obtained by curve fitting was 5.5 ± 0.6 nm. The surface plasmon resonance curves have been shown to be influenced by both NO2 and H2S. The effects were partly reversible, with lower detection limits of about 50 vapour parts per million

N. E. Agbor; J. P. Cresswell; M. C. Petty; A. P. Monkman

1997-01-01

71

A ATM I Materials Lifecycle Solutions Micro-Machined Thin Film H2 Gas Sensors  

E-print Network

-based cap layer Rare earth hydride H + YH2 + YH3 H2 2H 2H + ½O2 H2O ½O2 + CO CO2 0.6 0.4 0.2 0.0 H2 Solutions Device Model: Chemical, Electrical, Mechanical Rare earth hydridePd-based cap layer Rsensor = 2 hydride films ­ Thermally controlled chemi-resistive transduction Rare Earth Hydride Pd Barrier #12;A ATM

72

Effects of Ti addiction in WO 3 thin film ammonia gas sensor prepared by dc reactive magnetron sputtering  

NASA Astrophysics Data System (ADS)

WO 3 sensing films (1500 Å) were deposited using dc reactive magnetron sputtering method on alumina substrate on which patterned interdigital Pt electrodes were previously formed. The additive Ti was sputtered with different thickness (100-500 Å) onto WO 3 thin films and then the films as-deposited were annealed at 400°C in air for 3h. The crystal structure and chemical composition of the films were characterized by XRD and XPS analysis. The effect of Ti addition on sensitive properties of WO 3 thin film to the NH 3 gas was then discussed. WO 3 thin films added Ti revealed excellent sensitivity and response characteristics in the presence of low concentration of NH 3 (5-400 ppm) gas in air at 200°C operating temperature. Especially,in case 300 Å thickness of additive Ti, WO 3 thin films have a promotional effect on the response speed to NH 3 and selectivity enhanced with respect to other gases (CO, C IIH 5OH, CH 4). The influence of different substrates, including alumina, silicon and glass, on sensitivity to NH 3 gas has also been investigated.

Hu, Ming; Yong, Cholyun; Feng, Youcai; Lv, Yuqiang; Han, Lei; Liang, Jiran; Wang, Haopeng

2006-11-01

73

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

74

Sensing Properties of Pd-Loaded Co3O4 Film for a ppb-Level NO Gas Sensor.  

PubMed

We prepared 0.1 wt%-30 wt% Pd-loaded Co3O4 by a colloidal mixing method and investigated the sensing properties of a Pd-loaded Co3O4 sensor element, such as the sensor response, 90% response time, 90% recovery time, and signal-to-noise (S/N) ratio, toward low nitric oxide (NO) gas levels in the range from 50 to 200 parts per billion. The structural properties of the Pd-loaded Co3O4 powder were investigated using X-ray diffraction analysis and transmission electron microscopy. Pd in the powder existed as PdO. The sensor elements with 0.1 wt%-10 wt% Pd content have higher sensor properties than those without any Pd content. The response of the sensor element with a 30 wt% Pd content decreased markedly because of the aggregation and poor dispersibility of the PdO particles. High sensor response and S/N ratio toward the NO gas were achieved when a sensor element with 10 wt% Pd content was used. PMID:25853408

Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck; Sato, Kazuo

2015-01-01

75

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. PMID:22319350

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

2011-01-01

76

Calorimetric Gas Sensors.  

NASA Astrophysics Data System (ADS)

Calorimetric gas sensors measure the concentration of combustibles species by detecting the temperature rise resulting from the oxidation process on a catalytic element. These devices are widely used to monitor in air the concentration of flammable species close to their explosion limit. Recently, research and development efforts have been directed towards applying this technology to measure low concentrations of hydrocarbons in a gas mixture at elevated temperatures with little amount of excess oxygen. The presentation discusses the advantages of using batch-fabricated Si micromachined devices over larger ceramic-type calorimeters to achieve high sensitivity and a fast response time. The effects limiting the performance of these devices will also be explained.

Zanini, Margherita; Visser, J. H.; Nietering, K. E.; McBride, J. R.; Logothetis, E. M.

1998-03-01

77

Properties and sensor performance of zinc oxide thin films  

E-print Network

Reactively sputtered ZnO thin film gas sensors were fabricated onto Si wafers. The atmosphere dependent electrical response of the ZnO micro arrays was examined. The effects of processing conditions on the properties and ...

Min, Yongki, 1965-

2003-01-01

78

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. 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

79

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 tunneling. Adsorption of gaseous contaminant onto the layer of organic semiconductor modulates the tunneling current in a quantitative manner.

Hirschfeld, T.B.

1985-09-30

80

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

81

Bimodular high temperature planar oxygen gas sensor  

PubMed Central

A bimodular planar O2 sensor was fabricated using NiO nanoparticles (NPs) thin film coated yttria-stabilized zirconia (YSZ) substrate. The thin film was prepared by radio frequency (r.f.) magnetron sputtering of NiO on YSZ substrate, followed by high temperature sintering. The surface morphology of NiO NPs film was characterized by atomic force microscope (AFM) and scanning electron microscope (SEM). X-ray diffraction (XRD) patterns of NiO NPs thin film before and after high temperature O2 sensing demonstrated that the sensing material possesses a good chemical and structure stability. The oxygen detection experiments were performed at 500, 600, and 800°C using the as-prepared bimodular O2 sensor under both potentiometric and resistance modules. For the potentiometric module, a linear relationship between electromotive force (EMF) output of the sensor and the logarithm of O2 concentration was observed at each operating temperature, following the Nernst law. For the resistance module, the logarithm of electrical conductivity was proportional to the logarithm of oxygen concentration at each operating temperature, in good agreement with literature report. In addition, this bimodular sensor shows sensitive, reproducible and reversible response to oxygen under both sensing modules. Integration of two sensing modules into one sensor could greatly enrich the information output and would open a new venue in the development of high temperature gas sensors. PMID:25191652

Sun, Xiangcheng; Liu, Yixin; Gao, Haiyong; Gao, Pu-Xian; Lei, Yu

2014-01-01

82

Porous Nickel Oxide Film Sensor for Formaldehyde  

NASA Astrophysics Data System (ADS)

Formaldehyde is a volatile organic compound and a harmful indoor pollutant contributing to the "sick building syndrome". We used advanced gas deposition to fabricate highly porous nickel oxide (NiO) thin films for formaldehyde sensing. The films were deposited on Al2O3 substrates with prefabricated comb-structured electrodes and a resistive heater at the opposite face. The morphology and structure of the films were investigated with scanning electron microscopy and X-ray diffraction. Porosity was determined by nitrogen adsorption isotherms with the Brunauer-Emmett-Teller method. Gas sensing measurements were performed to demonstrate the resistive response of the sensors with respect to different concentrations of formaldehyde at 150 °C.

Cindemir, U.; Topalian, Z.; Österlund, L.; Granqvist, C. G.; Niklasson, G. A.

2014-11-01

83

STW gas sensors using plasma-polymerized allylamine  

Microsoft Academic Search

Gas sensors generally consist of two major components: a gas recognition element which provides the specificity and selectivity of the measurement and a physical transducer which translates the gas absorption or desorption event into electronic signal. In this paper, plasma polymerized allylamine (PPAa) film is used as a gas recognition element and a surface transverse wave (STW) device is used

Hiromi Yatsuda; Makoto Nara; Takashi Kogai; Hidenobu Aizawa; Shigeru Kurosawa

2007-01-01

84

Sensing Characteristics of Flame-Spray-Made Pt/ZnO Thick Films as H(2) Gas Sensor.  

PubMed

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 Al(2)O(3) 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 (H(2)) was found that the 0.2 at.% Pt/ZnO sensing film showed an optimum H(2) 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. PMID:22399971

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

2009-01-01

85

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. PMID:22399971

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

2009-01-01

86

Comparison of Gas Sensors Based on Oxygen Plasma-Treated Carbon Nanotube Network Films with Different Semiconducting Contents  

NASA Astrophysics Data System (ADS)

We report on the effect of oxygen plasma treatment on the performance of single-wall carbon nanotube (SWCNT) NH3 gas sensors with different semiconducting contents (66% and 90% semiconducting SWCNTs). The performance of chemical sensors based on SWCNT networks depends on the concentration of semiconducting SWCNTs (s-SWCNTs), whose conductance can be significantly modulated by the absorbed molecules and the surface functionalization. After oxygen plasma treatment, the 66% s-SWCNT sample showed an increase in sensitivity from 0.0275%/ppm to 0.1525%/ppm (5.5 times), while the 90% s-SWCNT device demonstrated an increase in sensitivity from 0.1184%/ppm to 1.5707%/ppm (13 times). These results correspond to improvements in sensitivity of 57 times and 10 times compared with pristine and plasma-treated 66% s-SWCNT samples, respectively. In addition, the plasma-treated sensors exhibited much faster response and recovery times than the pristine one. The large improvement in performance was explained by the presence of oxygen-containing functional groups and the sp2-sp3 structure change of SWCNTs, which changes the binding energy while increasing the uptake of polar molecules such as NH3.

Ham, Seung Woo; Hong, Hyun Pyo; Kim, Jin Woong; Kim, Jong Hyun; Kim, Ki Bum; Park, Chan Won; Min, Nam Ki

2015-01-01

87

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

88

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

89

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

90

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. PMID:22408529

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

2009-01-01

91

Microstructural characterization of a titanium-tungsten oxide gas sensor  

Microsoft Academic Search

Thin films of TiWO were prepared from a WTi alloy target by rf magnetron sputtering in reactive atmosphere. Analysis devoted to investigate the microstructural properties of this material was carried out in order to explain the origin for the high sensing performance of a WTi-oxide gas sensor. Scanning and transmission electron microscopy techniques showed that after annealing the film consists

Matteo Ferroni; Vincenzo Guidi; Giuliano Martinelli; Giorgio Sberveglieri

1997-01-01

92

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

93

Exhaust gas sensors for automotive emission control  

Microsoft Academic Search

This report gives an overview on ZrO2 automotive exhaust gas sensors, the development steps of thimble-type oxygen sensors and the technology and design of planar-type oxygen sensors. Furthermore, advanced exhaust gas sensor systems, catalyst monitoring sensors and future developments are described.

J Riegel; H Neumann; H.-M Wiedenmann

2002-01-01

94

Highly enhanced gas sensing in single-walled carbon nanotube-based thin-film transistor sensors by ultraviolet light irradiation  

PubMed Central

Single-walled carbon nanotube (SWCNT) random networks are easily fabricated on a wafer scale, which provides an attractive path to large-scale SWCNT-based thin-film transistor (TFT) manufacturing. However, the mixture of semiconducting SWCNTs and metallic SWCNTs (m-SWCNTs) in the networks significantly limits the TFT performance due to the m-SWCNTs dominating the charge transport. In this paper, we have achieved a uniform and high-density SWCNT network throughout a complete 3-in. Si/SiO2 wafer using a solution-based assembly method. We further utilized UV radiation to etch m-SWCNTs from the networks, and a remarkable increase in the channel current on/off ratio (Ion/Ioff) from 11 to 5.6 × 103 was observed. Furthermore, we used the SWCNT-TFTs as gas sensors to detect methyl methylphosphonate, a stimulant of benchmark threats. It was found that the SWCNT-TFT sensors treated with UV radiation show a much higher sensitivity and faster response to the analytes than those without treatment with UV radiation. PMID:23176557

2012-01-01

95

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

96

Model of detection for a modulated conductivity sensor: application for a NOx gas sensor  

Microsoft Academic Search

The performance of a chemical gas sensor based on polycristallyne tin oxide films is strongly related to their structure, thickness and doping. In previous works we have studied the influence of the thickness on the detection by impedance spectroscopy analysis [1,2]. In the present work we have focused our attention in designing and modelizing a sensor for detection of NOx

J. Gutierrez; L. Ares; J. I. Robla; I. Sayago; M. C. Horrillo; J. A. Agapito

1993-01-01

97

Sensors and Actuators B 118 (2006) 135141 Low temperature indium oxide gas sensors  

E-print Network

Sensors and Actuators B 118 (2006) 135­141 Low temperature indium oxide gas sensors M. Sucheaa combined with Fe2O3 additives was found to be 370 C. On the other hand, tin-doped indium oxide (ITO) has of nanocrystalline indium oxide (InOx) thin films was performed by dc magnetron sputtering. Detailed description

2006-01-01

98

MAPLE activities and applications in gas sensors  

NASA Astrophysics Data System (ADS)

During the last decade, many groups have grown thin films of various organic materials by the cryogenic Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique with a wide range of applications. This contribution is focused on the summary of our results with deposition and characterization of thin films of fibrinogen, pullulan derivates, azo-polyurethane, cryoglobulin, polyvinyl alcohol, and bovine serum albumin dissolved in physiological serum, dimethyl sulfoxide, sanguine plasma, phosphate buffer solution, H2O, ethylene glycol, and tert-butanol. MAPLE films were characterized using FTIR, AFM, Raman scattering, and SEM. For deposition, a special hardware was developed including a unique liquid nitrogen cooled target holder. Overview of MAPLE thin film applications is given. We studied SnAcAc, InAcAc, SnO2, porphyrins, and polypyrrole MAPLE fabricated films as small resistive gas sensors. Sensors were tested with ozone, nitrogen dioxide, hydrogen, and water vapor gases. In the last years, our focus was on the study of fibrinogen-based scaffolds for application in tissue engineering, wound healing, and also as a part of layers for medical devices.

Jelínek, Miroslav; Remsa, Jan; Kocourek, Tomáš; Kubešová, Barbara; Sch?rek, Jakub; Myslík, Vladimír

2011-11-01

99

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

100

TiO 2 thin films by a novel sol–gel processing for gas sensor applications  

Microsoft Academic Search

Novel thin films of titanium dioxide dispersed in a polymeric matrix have been prepared by a chemically modified sol–gel technique. Nanostructured films of pure TiO2 in the anatase form are obtained after annealing at 500°C. SEM, TEM and TG\\/DTA are used for the structure characterisation of TiO2 films. The role of the polymer in controlling the microstructure is confirmed. The

C Garzella; E Comini; E Tempesti; C Frigeri; G Sberveglieri

2000-01-01

101

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

102

Integrated thin film fluorescence NOx sensor concept  

Microsoft Academic Search

A fluorescence sensor system is proposed that integrates emission and detection methods as well as optical and electronic components in a thin film geometry. Predicted properties of this sensor include: increased sensitivity, shielding form unwanted radiation, wavelength filtering, potential operation at high temperatures, and miniaturization. The sensor can be tuned to measure a wide variety of species by varying its

Margaret L. Tuma; Russell W. Gruhlke

1997-01-01

103

Influence of microstructure of tungsten oxide thin films on their general performance as ozone and NOx gas sensors  

Microsoft Academic Search

Tungsten oxides thin films were obtained by electron beam deposition and annealed in the temperature range 350-800°C for 1-3 h. The structure, morphology and phase composition of the as-deposited and annealed films were characterized by X-ray diffraction and AFM. The electrical response towards NO2 and O3 was studied both experimentally and theoretically. In order to interprete the kinetic characteristics of

Olena Berger; Thomas Hoffmann; Wolf-Joachim Fischer; Valeri Melev

2003-01-01

104

Nanoscaled tin dioxide films processed from organotin-based hybrid materials: an organometallic route toward metal oxide gas sensors  

NASA Astrophysics Data System (ADS)

Nanocrystalline tin dioxide (SnO2) ultra-thin films were obtained employing a straightforward solution-based route that involves the calcination of bridged polystannoxane films processed by the sol-gel process from bis(triprop-1-ynylstannyl)alkylene and -arylene precursors. These films have been thoroughly characterized by FTIR, contact angle measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force (AFM) and scanning electron (SEM) microscopies. Annealing at a high temperature gave 30-35 nm thick cassiterite SnO2 films with a mean crystallite size ranging from 4 to 7 nm depending on the nature of the organic linker in the distannylated compound used as a precursor. In the presence of H2 and CO gases, these layers led to highly sensitive, reversible and reproducible responses. The sensing properties were discussed in regard to the crystallinity and porosity of the sensing body that can be tuned by the nature of the precursor employed. Organometallic chemistry combined with the sol-gel process therefore offers new possibilities toward metal oxide nanostructures for the reproducible and sensitive detection of combustible and toxic gases.Nanocrystalline tin dioxide (SnO2) ultra-thin films were obtained employing a straightforward solution-based route that involves the calcination of bridged polystannoxane films processed by the sol-gel process from bis(triprop-1-ynylstannyl)alkylene and -arylene precursors. These films have been thoroughly characterized by FTIR, contact angle measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force (AFM) and scanning electron (SEM) microscopies. Annealing at a high temperature gave 30-35 nm thick cassiterite SnO2 films with a mean crystallite size ranging from 4 to 7 nm depending on the nature of the organic linker in the distannylated compound used as a precursor. In the presence of H2 and CO gases, these layers led to highly sensitive, reversible and reproducible responses. The sensing properties were discussed in regard to the crystallinity and porosity of the sensing body that can be tuned by the nature of the precursor employed. Organometallic chemistry combined with the sol-gel process therefore offers new possibilities toward metal oxide nanostructures for the reproducible and sensitive detection of combustible and toxic gases. Electronic supplementary information (ESI) available: Additional information and figures concerning TGA-MS, WPS and surface morphology (SEM and AFM) of the TF2 samples. See DOI: 10.1039/c2nr31883k

Renard, Laetitia; Babot, Odile; Saadaoui, Hassan; Fuess, Hartmut; Brötz, Joachim; Gurlo, Aleksander; Arveux, Emmanuel; Klein, Andreas; Toupance, Thierry

2012-10-01

105

Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures  

PubMed Central

Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO) nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D) nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors. PMID:22778599

Gu, Haoshuang; Wang, Zhao; Hu, Yongming

2012-01-01

106

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

107

CO2 Selective Potentiometric Sensor in Thick-film Technology  

PubMed Central

A potentiometric sensor device based on screen-printed Nasicon films was investigated. In order to transfer the promising sensor concept of an open sodium titanate reference to thick film technology, “sodium-rich” and “sodium-poor” formulations were compared. While the “sodium-rich” composition was found to react with the ion conducting Nasicon during thermal treatment, the “sodium-poor” reference mixture was identified as an appropriate reference composition. Screen-printed sensor devices were prepared and tested with respect to CO2 response, reproducibility, and cross-interference of oxygen. Excellent agreement with the theory was observed. With the integration of a screen-printed heater, sensor elements were operated actively heated in a cold gas stream.

Sahner, Kathy; Schulz, Anne; Kita, Jaroslaw; Merkle, Rotraut; Maier, Joachim; Moos, Ralf

2008-01-01

108

Vibration welding system with thin film sensor  

DOEpatents

A vibration welding system includes an anvil, a welding horn, a thin film sensor, and a process controller. The anvil and horn include working surfaces that contact a work piece during the welding process. The sensor measures a control value at the working surface. The measured control value is transmitted to the controller, which controls the system in part using the measured control value. The thin film sensor may include a plurality of thermopiles and thermocouples which collectively measure temperature and heat flux at the working surface. A method includes providing a welder device with a slot adjacent to a working surface of the welder device, inserting the thin film sensor into the slot, and using the sensor to measure a control value at the working surface. A process controller then controls the vibration welding system in part using the measured control value.

Cai, Wayne W; Abell, Jeffrey A; Li, Xiaochun; Choi, Hongseok; Zhao, Jingzhou

2014-03-18

109

Enhanced response of SnO2 based thin film sensors towards methane gas due to the collective efforts of catalytic activity and photo-activation phenomenon  

NASA Astrophysics Data System (ADS)

Detection of methane is always a great cause of concern for safety productions in mines and chemical factories. The present study investigates the twin effect of UV illumination and catalytic activity on methane sensing characteristics of SnO2 sensors. The sensitivity and selectivity of pure SnO2 thin film sensors are improved by loading it with Pd catalyst clusters (8 nm). Further, optimizing the thickness of Pd clusters leads to an enhanced sensing response of 97% to 99% over a wider temperature range (160°C to 240°C) for 10 nm thick Pd clusters. The room temperature response of SnO2-Pd (10 nm) sensor increases to 99.7% under UV illumination (which was around 0.6% at room temperature under no illumination) which is attributed to the efficient catalytic dissociation of methane molecules besides the spillover process at room temperature. The present study therefore investigates the effect of UV illumination on methane sensing characteristics of SnO2 sensors loaded with Pd clusters. Results indicate the possibility of utilizing the sensor structure with novel dispersal of Pd catalyst clusters on SnO2 film surface for efficient detection of methane at room temperature under the illumination of UV radiations.

Haridas, D.; Gupta, V.

2015-02-01

110

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

111

Surface morphology-dependent room-temperature LaFeO? nanostructure thin films as selective NO? gas sensor prepared by radio frequency magnetron sputtering.  

PubMed

In the present work, perovskite LaFeO3 thin films with unique morphology were obtained on silicon substrate using radio frequency magnetron sputtering technique. The effect of thickness and temperature on the morphological and structural properties of LaFeO3 films was systematically studied. The X-ray diffraction pattern explored the highly oriented orthorhombic perovskite phase of the prepared thin films along [121]. Electron micrograph images exposed the network and nanocube surface morphology of LaFeO3 thin films with average sizes of ?90 and 70 nm, respectively. The developed LaFeO3 thin films not only possess unique morphology, but also influence the gas-sensing performance toward NO2. Among the two morphologies, nanocubes exhibited high sensitivity, good selectivity, fast response-recovery time, and excellent repeatability for 1 ppm level of NO2 gas at room temperature. The response time for nanocubes was 24-11 s with a recovery duration of 35-15 s less than the network structure. The sensitivity toward NO2 detection was found to be in the range 29.60-157.89. The enhancement in gas-sensing properties is attributed to their porous structure, surface morphology, numerous surface active sites, and the oxygen vacancies. The gas-sensing measurements demonstrate that the LaFeO3 sensing material is an outstanding candidate for NO2 detection. PMID:25029197

Thirumalairajan, S; Girija, K; Mastelaro, Valmor R; Ponpandian, N

2014-08-27

112

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

NASA Astrophysics Data System (ADS)

To investigate the sensing mechanism of SnO 2 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 the variation of the film temperature and this result reveals that there exist three different models of hydrogen interaction with the film surface or with the oxygen adsorbates on the surface, which depend on the film temperature at that time. The change of resistance of the films shows quick saturation, while that of the work function has trends of slow and continuous decreasing; from these results, it is concluded that the adsorption or desorption of the oxidizing or reducing gases on the film surface are contributed mainly to the change of potential barrier of grain boundaries of the films.

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

1996-07-01

113

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

114

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

115

Polycrystalline-silicon microbridge combustible gas sensor  

NASA Astrophysics Data System (ADS)

Catalytic, calorimetric gas detection is the most commonly used method for the detection of combustible gases below the lower-explosive limit (LEL). In this method, the heat of oxidation of a combustible species on a heated catalyst surface is detected by a resistance thermometer in proximity. Conventionally fabricated sensors suffer from high-power consumption (˜500 mW), slow thermal response (˜15 sec) and low thermal sensitivity (1-2sp°C/mW). Fully CMOS-compatible, surface-micromachined polysilicon bridges have been fabricated for use in catalytic, calorimetric gas detection and are characterized by low-power consumption (35 mW), fast response (0.2 msec) and high sensitivity (16sp°C/mW). The batch fabrication techniques used here significantly increase the manufacturability of these devices as compared with their conventional predecessors, since hand manufacture/sorting conventionally used ate eliminated. A post-processing, post-packaging micro-chemical-vapor-deposition technique was developed for the purpose of selectively depositing catalytic films only in the active area of the sensor. Film microstructure was modified using a pulsed-deposition technique and in situ methods of film growth monitoring were investigated. With a Pt catalyst, ultimate device sensitivity to hydrogen was 100 ppm in air. To predict device response, knowledge of the temperature distribution along a microbridge is required. Both analytical and numerical techniques were used to model this distribution and are in good agreement with measurements obtained by infrared microscopy, For modeling purposes the temperature dependence of the thermal and electrical conductivity of polysilicon at high temperature ({>}300sp°C) were measured using microbridges outfitted with special high-temperature bond pads. Physical models of thermal and electrical conduction in polysilicon were constructed.

Manginell, Ronald Paul

116

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

117

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

118

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

119

Gas sensor with attenuated drift characteristic  

DOEpatents

A sensor with an attenuated drift characteristic, including a layer structure in which a sensing layer has a layer of diffusional barrier material on at least one of its faces. The sensor may for example be constituted as a hydrogen gas sensor including a palladium/yttrium layer structure formed on a micro-hotplate base, with a chromium barrier layer between the yttrium layer and the micro-hotplate, and with a tantalum barrier layer between the yttrium layer and an overlying palladium protective layer. The gas sensor is useful for detection of a target gas in environments susceptible to generation or incursion of such gas, and achieves substantial (e.g., >90%) reduction of signal drift from the gas sensor in extended operation, relative to a corresponding gas sensor lacking the diffusional barrier structure of the invention

Chen, Ing-Shin (Danbury, CT) [Danbury, CT; Chen, Philip S. H. (Bethel, CT) [Bethel, CT; Neuner, Jeffrey W. (Bethel, CT) [Bethel, CT; Welch, James (Fairfield, CT) [Fairfield, CT; Hendrix, Bryan (Danbury, CT) [Danbury, CT; Dimeo, Jr., Frank [Danbury, CT

2008-05-13

120

Zinc oxide thin film acoustic sensor  

NASA Astrophysics Data System (ADS)

This paper reports the implementation of (750 nm) thickness of Zinc Oxide (ZnO) thin film for the piezoelectric pressure sensors. The film was prepared and deposited employing the spray pyrolysis technique. XRD results show that the growth preferred orientation is the (002) plane. A polycrystalline thin film (close to mono crystallite like) was obtained. Depending on the Scanning Electron Microscopy photogram, the film homogeneity and thickness were shown. The resonance frequency measured (about 19 kHz) and the damping coefficient was calculated and its value was found to be about (2.5538), the thin film be haves as homogeneous for under and over damped. The thin film pressure sensing was approximately exponentially related with frequency, the thin film was observed to has a good response for mechanical stresses also it is a good material for the piezoelectric properties.

Mohammed, Ali Jasim; Salih, Wafaa Mahdi; Hassan, Marwa Abdul Muhsien; Mansour, Hazim Louis; Nusseif, Asmaa Deiaa; Kadhum, Haider Abdullah

2013-12-01

121

Zinc oxide thin film acoustic sensor  

SciTech Connect

This paper reports the implementation of (750 nm) thickness of Zinc Oxide (ZnO) thin film for the piezoelectric pressure sensors. The film was prepared and deposited employing the spray pyrolysis technique. XRD results show that the growth preferred orientation is the (002) plane. A polycrystalline thin film (close to mono crystallite like) was obtained. Depending on the Scanning Electron Microscopy photogram, the film homogeneity and thickness were shown. The resonance frequency measured (about 19 kHz) and the damping coefficient was calculated and its value was found to be about (2.5538), the thin film be haves as homogeneous for under and over damped. The thin film pressure sensing was approximately exponentially related with frequency, the thin film was observed to has a good response for mechanical stresses also it is a good material for the piezoelectric properties.

Mohammed, Ali Jasim; Salih, Wafaa Mahdi; Hassan, Marwa Abdul Muhsien; Nusseif, Asmaa Deiaa; Kadhum, Haider Abdullah [Department of Physics , College of Science, Al-Mustansiriyah University, Baghdad (Iraq); Mansour, Hazim Louis [Department of Physics , College of Education, Al-Mustansiriyah University, Baghdad (Iraq)

2013-12-16

122

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. PMID:23529123

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

2013-01-01

123

Sensors and Actuators B 49 (1998) 258267 Pd/PVDF thin film hydrogen sensor based on  

E-print Network

Sensors and Actuators B 49 (1998) 258­267 Pd/PVDF thin film hydrogen sensor based on laser thin film coated on a polymeric membrane, optical reflectance and transmittance signals are generated polyvinilydene fluoride (PVDF) thin-film photopy- roelectric (PPE) sensors [1,2]. The PPE sensor exhibits

Mandelis, Andreas

124

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

125

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

126

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

127

Temperature Modulation of a Catalytic Gas Sensor  

PubMed Central

The use of catalytic gas sensors usually offers low selectivity, only based on their different sensitivities for various gases due to their different heats of reaction. Furthermore, the identification of the gas present is not possible, which leads to possible misinterpretation of the sensor signals. The use of micro-machined catalytic gas sensors offers great advantages regarding the response time, which allows advanced analysis of the sensor response. By using temperature modulation, additional information about the gas characteristics can be measured and drift effects caused by material shifting or environmental temperature changes can be avoided. In this work a miniaturized catalytic gas sensor which offers a very short response time (<150 ms) was developed. Operation with modulated temperature allows analysis of the signal spectrum with advanced information content, based on the Arrhenius approach. Therefore, a high-precise electronic device was developed, since theory shows that harmonics induced by the electronics must be avoided to generate a comprehensible signal. PMID:25356643

Brauns, Eike; Morsbach, Eva; Kunz, Sebastian; Baeumer, Marcus; Lang, Walter

2014-01-01

128

Temperature modulation of a catalytic gas sensor.  

PubMed

The use of catalytic gas sensors usually offers low selectivity, only based on their different sensitivities for various gases due to their different heats of reaction. Furthermore, the identification of the gas present is not possible, which leads to possible misinterpretation of the sensor signals. The use of micro-machined catalytic gas sensors offers great advantages regarding the response time, which allows advanced analysis of the sensor response. By using temperature modulation, additional information about the gas characteristics can be measured and drift effects caused by material shifting or environmental temperature changes can be avoided. In this work a miniaturized catalytic gas sensor which offers a very short response time (<150 ms) was developed. Operation with modulated temperature allows analysis of the signal spectrum with advanced information content, based on the Arrhenius approach. Therefore, a high-precise electronic device was developed, since theory shows that harmonics induced by the electronics must be avoided to generate a comprehensible signal. PMID:25356643

Brauns, Eike; Morsbach, Eva; Kunz, Sebastian; Baeumer, Marcus; Lang, Walter

2014-01-01

129

Formaldehyde Gas Sensors: A Review  

PubMed Central

Many methods based on spectrophotometric, fluorometric, piezoresistive, amperometric or conductive measurements have been proposed for detecting the concentration of formaldehyde in air. However, conventional formaldehyde measurement systems are bulky and expensive and require the services of highly-trained operators. Accordingly, the emergence of sophisticated technologies in recent years has prompted the development of many microscale gaseous formaldehyde detection systems. Besides their compact size, such devices have many other advantages over their macroscale counterparts, including a real-time response, a more straightforward operation, lower power consumption, and the potential for low-cost batch production. This paper commences by providing a high level overview of the formaldehyde gas sensing field and then describes some of the more significant real-time sensors presented in the literature over the past 10 years or so. PMID:23549368

Chung, Po-Ren; Tzeng, Chun-Ta; Ke, Ming-Tsun; Lee, Chia-Yen

2013-01-01

130

Nanocrystalline films for gas-reactive applications  

DOEpatents

A gas sensor for detection of oxidizing and reducing gases, including O.sub.2, CO.sub.2, CO, and H.sub.2, monitors the partial pressure of a gas to be detected by measuring the temperature rise of an oxide-thin-film-coated metallic line in response to an applied electrical current. For a fixed input power, the temperature rise of the metallic line is inversely proportional to the thermal conductivity of the oxide coating. The oxide coating contains multi-valent cation species that change their valence, and hence the oxygen stoichiometry of the coating, in response to changes in the partial pressure of the detected gas. Since the thermal conductivity of the coating is dependent on its oxygen stoichiometry, the temperature rise of the metallic line depends on the partial pressure of the detected gas. Nanocrystalline (<100 nm grain size) oxide coatings yield faster sensor response times than conventional larger-grained coatings due to faster oxygen diffusion along grain boundaries rather than through grain interiors.

Eastman, Jeffrey A.; Thompson, Loren J.

2004-02-17

131

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

132

Composite optical waveguide composed of a tapered film of bromothymol blue evaporated onto a potassium ion-exchanged waveguide and its application as a guided wave absorption-based ammonia-gas sensor.  

PubMed

For what is the first time to our knowledge, we have successfully evaporated a tapered film of bromothymol blue (BTB) onto a potassium ion-exchanged (PIE) waveguide to form a composite optical waveguide (COWG) for trace-ammonia detection. The BTB film has a high refractive index (1.69) and a smooth surface and is transparent to a 633-nm laser beam in air. In the COWG structure, the BTB film serves as a single-mode waveguide, and adiabatic transition of the TE(0) mode was realized between the BTB waveguide and the PIE waveguide with both BTB tapers. In the presence of ammonia, the BTB film changes color from yellow to blue, which causes absorption of the 633-nm guided wave. Our experimental results demonstrate that such a guided wave absorption-based ammonia-gas sensor is much more sensitive than one based on evanescent-wave absorption. A detection limit of part in 10(9) of ammonia has been realized for a BTB film-PIE glass COWG. PMID:18040405

Qi, Z M; Yimit, A; Itoh, K; Murabayashi, M; Matsuda, N; Takatsu, A; Kato, K

2001-05-01

133

Optimization of Ormosil Films for Optical Sensor Applications  

Microsoft Academic Search

Recent work has indicated that Ormosil films, fabricated from organically modified precursors, produce better sensor performance for some specific applications, compared to films fabricated from conventional sol-gel precursors such as TEOS or TMOS. This paper aims to compare film properties and sensor behavior for films fabricated from tetraethoxysilane (TEOS) and tetramethoxysilane (TMOS) silica precursors and both methyltrimethoxysilane (MTMS) and methyltriethoxysilane

P. Lavin; C. M. McDonagh; B. D. MacCraith

1998-01-01

134

Augmenting Film and Video Footage with Sensor Data  

E-print Network

Augmenting Film and Video Footage with Sensor Data Norman Makoto Su, Heemin Park , Eric Bostrom of Electrical Engineering, School of Theater, Film and Television University of California, Los Angeles normsu application of sensor networks to the film industry. In particular, we are interested in augmenting film

Su, Norman Makoto

135

Enhancement of NH3 Gas Sensitivity at Room Temperature by Carbon Nanotube-Based Sensor Coated with Co Nanoparticles  

PubMed Central

Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH3 gas sensing applications. The MWCNT-based sensor is sensitive to NH3 gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH3, compared with alcohol and LPG. PMID:23364198

Nguyen, Lich Quang; Phan, Pho Quoc; Duong, Huyen Ngoc; Nguyen, Chien Duc; Nguyen, Lam Huu

2013-01-01

136

Enhancement of NH3 gas sensitivity at room temperature by carbon nanotube-based sensor coated with Co nanoparticles.  

PubMed

Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH(3) gas sensing applications. The MWCNT-based sensor is sensitive to NH(3) gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH(3), compared with alcohol and LPG. PMID:23364198

Nguyen, Lich Quang; Phan, Pho Quoc; Duong, Huyen Ngoc; Nguyen, Chien Duc; Nguyen, Lam Huu

2013-01-01

137

A microelectronic gas sensor for automotive applications: Characterization of device structure and gas sensitivity  

NASA Astrophysics Data System (ADS)

As the environmental protection agency requires increasingly stringent automotive emission controls, new sensor technologies are needed to replace the present oxygen sensors used for air to fuel ratio control. This thesis evaluates the viability of silicon-based microfabricated gas sensors for direct emissions measurements. The chemical sensors consisted of a 1.3 ?m\\ SiOsb2/Sisb3Nsb4 membrane supported by a 500 mum silicon rim. A heater and a pair of temperature sensors (TSRs) are suspended from the membrane, while thin films of platinum, gold, and titanium were deposited on top of the membrane for use as gas sensitive films. The structural stability of these devices was tested by exposing them to thermal cycles, pressure shocks, and mechanical vibrations. Several devices that were cycled in temperature over 408,000 times showed remarkable stability up to 650sp°C. The sensitivity of various films was measured by exposing the devices to parts per million (ppm) levels of hydrogen, carbon monoxide (CO), or propylene at elevated temperatures in the presence of excess oxygen. Changes in film resistance and temperature were used as measures of sensor response to gases. For example, in response to 500 ppm hydrogen exposure at 300sp°C, the Pt/Ti film resistance changed by approximately 10%. The thermal response of some Pt/Ti devices to 2500 ppm propylene was approximately 1.5sp°C. Decreased film resistance upon introduction of analyte gases was observed and could be attributed to the increased number of charge carriers or increased charge carrier mobility. Pure platinum and Pt/Ti films were more sensitive to hydrogen than either CO or propylene. The response to all three analytes increased with increasing temperatures. Oxidation of the analyte gases resulted in a measurable temperature increase. This calorimetric effect on Pt/Ti and Au/Ti films was investigated as a method of chemical sensing. The gold containing films showed both thermal and resistive responses to propylene and CO at lower temperatures than the Pt/Ti films. Comparing the relative response of different sensing films and utilizing different sensing methods appears to be a promising approach for gas species differentiation in sensor arrays.

Patel, Sanjay Virendra

138

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

139

Selective filter for SnO 2-based gas sensor: application to hydrogen trace detection  

Microsoft Academic Search

The main drawback of the SnO2-based gas sensors is their low selectivity. In this study, we present a highly selective hydrogen sensor with minimum cross sensitivity to ethanol, methane, carbon monoxide and hydrogen sulfide. Thick film SnO2 sensors are treated by hexamethyldisiloxane (HMDS) at high temperature (500–600°C). After this treatment, the electrical properties of sensors are greatly modified: the sensitivity

G. Tournier; C. Pijolat

2005-01-01

140

Mechanical Drawing of Gas Sensors on Paper  

E-print Network

Pencil it in: Mechanical abrasion of compressed single-walled carbon nanotubes (SWCNTs) on the surface of paper produces sensors capable of detecting NH[subscript 3] gas at sub-ppm concentrations. This method of fabrication ...

Esser, Birgit

141

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

142

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

143

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

144

Effects of Palladium Loading on the Response of a Thick Film Flame-made ZnO Gas Sensor for Detection of Ethanol Vapor  

PubMed Central

ZnO nanoparticles doped with 0-5 mol% Pd were successfully produced in a single step by flame spray pyrolysis (FSP) using zinc naphthenate and palladium (II) acetylacetonate dissolved in toluene-acetonitrile (80:20 vol%) as precursors. The effect of Pd loading on the ethanol gas sensing performance of the ZnO nanoparticles and the crystalline sizes were investigated. The particle properties were analyzed by XRD, BET, AFM, SEM (EDS line scan mode), TEM, STEM, EDS, and CO-pulse chemisorption measurements. A trend of an increase in specific surface area of samples and a decrease in the dBET with increasing Pd concentrations was noted. ZnO nanoparticles were observed as particles presenting clear spheroidal, hexagonal and rod-like morphologies. The sizes of ZnO spheroidal and hexagonal particle crystallites were in the 10-20 nm range. ZnO nanorods were in the range of 10-20 nm in width and 20-50 nm in length. The size of Pd nanoparticles increased and Pd-dispersion% decreased with increasing Pd concentrations. The sensing films were produced by mixing the particles into an organic paste composed of terpineol and ethyl cellulose as a vehicle binder. The paste was doctor-bladed onto Al2O3 substrates interdigitated with Au electrodes. The film morphology was analyzed by SEM and EDS analyses. The gas sensing of ethanol (25-250 ppm) was studied in dry air at 400°C. The oxidation of ethanol on the sensing surface of the semiconductor was confirmed by MS. A well-dispersed of 1 mol%Pd/ZnO films showed the highest sensitivity and the fastest response time (within seconds).

Liewhiran, Chaikarn; Phanichphant, Sukon

2007-01-01

145

Temperature compensation for hot-film crosswind sensors  

Microsoft Academic Search

An approach to calibrate temperature compensation for hot-film crosswind sensors is proposed. The crosswind sensor consists of a pair of platinum films which are closely spaced by the bridging material. A resistive thermal detector (RTD) with positive temperature coefficient is employed to compensate for variations in ambient temperature. Given the temperature coefficients of platinum films and the RTD, temperature compensation

Anshi Chen; Jing Zu; Bin Li

1997-01-01

146

Study on PD detection in SF6 using multi-wall carbon nanotube films sensor  

Microsoft Academic Search

The detection of partial discharge (PD) and the analysis of SF6 gas components in gas insulated switchgear (GIS) have great significance for the fault diagnosis and running state assessment of power equipments. In this paper, a method of detecting SF6 decomposition components caused by PD is proposed. Accordingly, multi-wall carbon nanotube (MWNT) films sensors which is used to detect PD

Xiao-xing Zhang; Wang-ting Liu; Ju Tang; Peng Xiao

2010-01-01

147

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

148

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

149

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

150

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

151

NOx sensor using YBa 2Cu 3O 7 ? ? thin films  

Microsoft Academic Search

The aim of our study is to develop NOx sensors that can measure NOx concentrations in exhaust gas. The present study investigates the gas-sensing properties of YBa2Cu3O7 ? ? thin films, deposited on a SrTiO3 substrate by the ion-beam sputtering method. The thin film we made exhibits high sensitivity to NO at 350 °C, and the NO sensitivity increases with

S Kudo; H Ohnishi; T Matsumoto; M Ippommatsu

1995-01-01

152

A portable gas sensor based on cataluminescence.  

PubMed

We describe a portable gas sensor based on cataluminescence. Miniaturization of the gas sensor was achieved by using a miniature photomultiplier tube, a miniature gas pump and a simple light seal. The signal to noise ratio (SNR) was considered as the evaluation criteria for the design and testing of the sensor. The main source of noise was from thermal background. Optimal working temperature and flow rate were determined experimentally from the viewpoint of improvement in SNR. A series of parameters related to analytical performance was estimated. The limitation of detection of the sensor was 7 ppm (SNR = 3) for ethanol and 10 ppm (SNR = 3) for hydrogen sulphide. Zirconia and barium carbonate were respectively selected as nano-sized catalysts for ethanol and hydrogen sulphide. PMID:22736626

Kang, C; Tang, F; Liu, Y; Wu, Y; Wang, X

2013-01-01

153

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. PMID:22163805

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

2011-01-01

154

Development and characterization of a sprayed ZnO thin film-based NO2 sensor  

NASA Astrophysics Data System (ADS)

NO2 is one of the most harmful gases nowadays. A NO2 sensor based on sprayed ZnO thin film is reported in this work. Indium additive is used to improve the sensor performance, i.e. on the sensor response as well as on the sensor impedance, is studied. It was demonstrated that by adding 3 wt% of indium acetate to the spraying solution it is possible to enhance the film gas-response to 5 ppm of NO2 at 275 °C. At the same time the electrical resistance of the ZnO thin films significantly decreases in this case as a result of an effective doping process. Furthermore, the dependence of the electrical resistance on temperature in several gas atmospheres was also studied. The surface roughness was measured by atomic force microscopy (AFM). It was observed that doping increases the surface roughness and this fact plays an important role in the sensitization mechanism.

Ferro, R.; Rodriguez, J. A.; Bertrand, P.

2005-08-01

155

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

156

Study on Fiber-optic Hydrogen Sulfide Gas Sensor  

NASA Astrophysics Data System (ADS)

We describe a novel fiber-optic gas sensor which hydrogen Sulfide (H2S) gas can be detected by a silver coated fiber bragg grating (FBG). The H2S sensitive material Ag can be coated on the cladding surrounding surface of FBG by conventional silver mirror reaction. The scanning electron microscope (SEM) was applied to analysis the Ag film structure before and after the interaction with H2S gas. By conducting the experiment of Ag-coated optical sensor (AOS), the relation between the H2S gas concentration and absorption spectrum was built. Result shows that while the concentration alters from 0 to 9.32%, a linear response of AOS signal to H2S concentration was observed with the response sensitivity of 0.332 dBm/% and linearity R2=0.9966. Such H2S sensor is suitable for monitoring the H2S hazard as a one time disposable logging-while-drilling sensor.

Zhou, Hong; Wen, Jun-Qing; Zhang, Xiao-Zhen; Wang, Wei; Feng, De-Quan; Wang, Qi; Jia, Fei

157

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

158

Tunable fiber ring laser absorption spectroscopic sensors for gas detection  

NASA Astrophysics Data System (ADS)

Fiber-optic gas sensing techniques are commonly based on the recognition of a wide range of chemical species from characteristic absorption, fluorescence or Raman-scattering spectra signatures. By tuning over the vibrational lines of species in the path of laser beam, tunable diode laser gas sensors measure signal spectroscopic intensity, gas concentration, and other properties. However, they have limitations of bulk architecture, small change of signal on top of large background, and low sensitivity of direct absorption. Here we report the fabrication and optical measurements of tunable Er-doped fiber ring laser absorption spectroscopic sensor featuring a gas cell that is a segment of photonic crystal fiber (PCF) with a long-period grating (LPG) inscribed. The tunable laser beam is coupled into the cladding of the PCF by the LPG where the gas in air holes absorbs light. The light travels along the PCF cladding and reflects at the end of the fiber where a silver film is coated as a mirror at one end facet. The light propagates back within cladding and passes through the gas one more time thus increasing the interaction length. This light is finally recoupled into the fiber core for intensity measurement. The proposed fiber gas sensors have been experimentally used for ammonia (NH3) concentration detection. They show excellent sensitivity and selectivity, and are minimally affected by temperature and/or humidity changes. The sensors using PCF-LPG gas cell are simple to fabricate, cost-effective, and are deployed for a variety of applications not possible using conventional optical fibers.

Zheng, Shijie; Zhu, Yinian; Krishnaswamy, Sridhar

2013-04-01

159

Smart single-chip gas sensor microsystem.  

PubMed

Research activity in chemical gas sensing is currently directed towards the search for highly selective (bio)chemical layer materials, and to the design of arrays consisting of different partially selective sensors that permit subsequent pattern recognition and multi-component analysis. Simultaneous use of various transduction platforms has been demonstrated, and the rapid development of integrated-circuit technology has facilitated the fabrication of planar chemical sensors and sensors based on three-dimensional microelectromechanical systems. Complementary metal-oxide silicon processes have previously been used to develop gas sensors based on metal oxides and acoustic-wave-based sensor devices. Here we combine several of these developments to fabricate a smart single-chip chemical microsensor system that incorporates three different transducers (mass-sensitive, capacitive and calorimetric), all of which rely on sensitive polymeric layers to detect airborne volatile organic compounds. Full integration of the microelectronic and micromechanical components on one chip permits control and monitoring of the sensor functions, and enables on-chip signal amplification and conditioning that notably improves the overall sensor performance. The circuitry also includes analog-to-digital converters, and an on-chip interface to transmit the data to off-chip recording units. We expect that our approach will provide a basis for the further development and optimization of gas microsystems. PMID:11713525

Hagleitner, C; Hierlemann, A; Lange, D; Kummer, A; Kerness, N; Brand, O; Baltes, H

2001-11-15

160

Smart single-chip gas sensor microsystem  

NASA Astrophysics Data System (ADS)

Research activity in chemical gas sensing is currently directed towards the search for highly selective (bio)chemical layer materials, and to the design of arrays consisting of different partially selective sensors that permit subsequent pattern recognition and multi-component analysis. Simultaneous use of various transduction platforms has been demonstrated, and the rapid development of integrated-circuit technology has facilitated the fabrication of planar chemical sensors and sensors based on three-dimensional microelectromechanical systems. Complementary metal-oxide silicon processes have previously been used to develop gas sensors based on metal oxides and acoustic-wave-based sensor devices. Here we combine several of these developments to fabricate a smart single-chip chemical microsensor system that incorporates three different transducers (mass-sensitive, capacitive and calorimetric), all of which rely on sensitive polymeric layers to detect airborne volatile organic compounds. Full integration of the microelectronic and micromechanical components on one chip permits control and monitoring of the sensor functions, and enables on-chip signal amplification and conditioning that notably improves the overall sensor performance. The circuitry also includes analog-to-digital converters, and an on-chip interface to transmit the data to off-chip recording units. We expect that our approach will provide a basis for the further development and optimization of gas microsystems.

Hagleitner, C.; Hierlemann, A.; Lange, D.; Kummer, A.; Kerness, N.; Brand, O.; Baltes, H.

2001-11-01

161

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

162

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

163

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

164

A harsh environment, multi-plasma microsystem with pressure sensor, gas purifier, and chemical detector  

Microsoft Academic Search

A system for gas phase chemical detection in harsh environments has been developed that utilizes three microplasma-based devices: pressure sensor, gas purifier, and optical emission sensor. The devices all utilize microplasmas between thin-film electrodes and occupy a combined active area of 10.5 mm2. They are fabricated on glass chips and enclosed in a 0.33 cm3 ceramic package. The optical emission

Scott A. Wright; Yogesh B. Gianchandani

2007-01-01

165

Tin oxide gas sensor fabricated using CMOS micro-hotplates and in-situ processing  

Microsoft Academic Search

A monolithic tin oxide (SnO2) gas sensor realized by commercial CMOS foundry fabrication (MOSIS) and postfabrication processing techniques is reported. The device is composed of a sensing film that is sputter-deposited on a silicon micromachined hotplate. The fabrication technique requires no masking and utilizes in situ process control and monitoring of film resistivity during film growth. Microhotplate temperature is controlled

John S. Suehle; Richard E. Cavicchi; Michael Gaitan; Steve Semancik

1993-01-01

166

Optimization of a wafer-level process for the fabrication of highly reproducible thin-film MOX sensors  

Microsoft Academic Search

Thin-film metal oxide semiconductor (MOX) gas sensors are characterized by high sensitivity and fast response. Those characteristics make them very promising among the several existing technologies for the production of solid state gas sensors. Furthermore, by means of silicon micro-machining technology, MOX sensors can be made on micro hotplates, allowing to reach very low-power consumption, and the batch production guaranties

I. Elmi; S. Zampolli; G. C. Cardinali

2008-01-01

167

A bubble-based microfluidic gas sensor for gas chromatographs.  

PubMed

We report a new proof-of-concept bubble-based gas sensor for a gas chromatography system, which utilizes the unique relationship between the diameters of the produced bubbles with the gas types and mixture ratios as a sensing element. The bubble-based gas sensor consists of gas and liquid channels as well as a nozzle to produce gas bubbles through a micro-structure. It utilizes custom-developed software and an optical camera to statistically analyze the diameters of the produced bubbles in flow. The fabricated gas sensor showed that five types of gases (CO2, He, H2, N2, and CH4) produced (1) unique volumes of 0.44, 0.74, 1.03, 1.28, and 1.42 nL (0%, 68%, 134%, 191%, and 223% higher than that of CO2) and (2) characteristic linear expansion coefficients (slope) of 1.38, 2.93, 3.45, 5.06, and 5.44 nL/(kPa (?L s(-1))(-1)). The gas sensor also demonstrated that (3) different gas mixture ratios of CO2?:?N2 (100?:?0, 80?:?20, 50?:?50, 20?:?80 and 0?:?100) generated characteristic bubble diameters of 48.95, 77.99, 71.00, 78.53 and 99.50 ?m, resulting in a linear coefficient of 10.26 ?m (?L s(-1))(-1). It (4) successfully identified an injection (0.01 ?L) of pentane (C5) into a continuous carrier gas stream of helium (He) by monitoring bubble diameters and creating a chromatogram and demonstrated (5) the output stability within only 5.60% variation in 67 tests over a month. PMID:25350655

Bulbul, Ashrafuzzaman; Kim, Hanseup

2015-01-01

168

Multiple sensor array based on pure and surface modified WO3 thin films for e-nose application  

NASA Astrophysics Data System (ADS)

A 2 × 3 sensor array based on pure, Au and CuO modified (two of each kind) WO3 films was fabricated for e-nose application. Effect of surface modification has been investigated and correlated with the observed sensor response values. The sensor array was able to detect H2S,NH3 and NO selectively based on the sensor response pattern exhibited by the sensor array. WO3 sensor film modified with CuO exhibited a maximum sensitivity towards H2S (S = 92, 10 ppm, 250°C) while pure WO3 films exhibited better sensing characteristics towards NO (S=2.3, 10 ppm, 300°C) and NH3 (S=4.5, 50 ppm, 300°C). The shape of the curve remains unaltered by the change in the concentration of the gas. The shape and position of the combined response curve could be used to determine an unknown gas both qualitatively and quantitatively.

Goyal, C. P.; Ramgir, N. S.; Sharma, P. K.; Datta, N.; Kailasaganapathi, S.; Kaur, M.; Debnath, A. K.; Haque, F. Z.; Aswal, D. K.; Gupta, S. K.

2013-06-01

169

Development of a thin film solid state gaseous HCl sensor  

NASA Technical Reports Server (NTRS)

The selection of materials to develop a thin film HCl sensor is discussed. Data were primarily concerned with chemical and physical properties of the film and with electrical properties which exhibit and enhance electrical response when HCl is absorbed on the film surface. Techniques investigated for enhancing electrical response include changing conditions for growing films, adding impurities to the film, changing ambient light intensity, and altering the ambient temperature of the sensing element.

1975-01-01

170

Gas-sensitive holographic sensors  

E-print Network

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 4.38 Holographic response to atmospheric gases at different temperatures. 94 4.39 Holographic response versus temperature for all gaseous hydrocar- bons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 4.40 Correlation... in the stratosphere differ from those in other atmo- spheric layers [2–4]. In fact, with industrialization and increased consumption of gas products for daily use, certain gas molecules accumulate in cities and indoor environments [5]. Numerous human activities...

Martínez Hurtado, Juan Leonardo

2013-04-16

171

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

172

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

173

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

174

Polymer waveguide sensor with tin oxide thin film integrated onto optical-electrical printed circuit board  

NASA Astrophysics Data System (ADS)

In this study, we proposed and fabricated optical sensor module integrated onto optical-electrical printed circuit board (PCB) for gas detection based on polymer waveguide with tin oxide thin film. Their potential application as gas sensors are confirmed through computational simulation using the two dimensional finite-difference time-domain method (2DFDTD). Optical-electrical PCB was integrated into vertical cavity surface emitting laser (VCSEL), photodiode and polymeric sensing device was fabricated by the nano-imprint lithography technique. SnO2 thin film of 100nm thickness was placed on the surface of core layer exposed by removing the specific area of the upper cladding layer of 300 ?m length and 50 ?m width. The performance of the device was measured experimentally. Initial study on the sensor performance for carbon monoxide gas detection indicated good sensitivity.

Lim, Jung Woon; Kim, Seon Hoon; Kim, Jong-Sup; Kim, Jeong Ho; Kim, Yune Hyoun; Lim, Ju Young; Im, Young-Eun; Park, Jong Bok; Hann, Swook

2014-05-01

175

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

176

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. PMID:22219672

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

2010-01-01

177

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

178

Enhanced electrodes for solid state gas sensors  

DOEpatents

A solid state gas sensor generates an electrical potential between an equilibrium electrode and a second electrode indicative of a gas to be sensed. A solid electrolyte substrate has the second electrode mounted on a first portion of the electrolyte substrate and a composite equilibrium electrode including conterminous transition metal oxide and Pt components mounted on a second portion of the electrolyte substrate. The composite equilibrium electrode and the second electrode are electrically connected to generate an electrical potential indicative of the gas that is being sensed. In a particular embodiment of the present invention, the second electrode is a reference electrode that is exposed to a reference oxygen gas mixture so that the electrical potential is indicative of the oxygen in a gas stream.

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

2001-01-01

179

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

180

MEMS oscillating squeeze-film pressure sensor with optoelectronic feedback  

NASA Astrophysics Data System (ADS)

This work reports on an oscillating pressure sensor that converts pressure into frequency using the squeeze-film effect. A new aspect is the laser Doppler vibrometer (LDV) in the optoelectronic feedback loop that is used to bring the sensor element into sustained mechanical oscillation. A phase shifter and automatic gain control circuit stabilize the oscillation. The frequency stability of the pressure sensor is investigated by measuring its Allan deviation and is compared to the performance of a quartz oscillating pressure sensor. Finally, the pressure resolution of this oscillating sensor is compared to conventional pressure sensors.

Kumar, Lalit; Reimann, Klaus; Goossens, Martijn J.; Besling, Willem F. A.; Dolleman, Robin J.; Pijnenburg, Remco H. W.; van der Avoort, Cas; Sarro, Lina P. M.; Steeneken, Peter G.

2015-04-01

181

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

182

Printable polythiophene gas sensor array for low-cost electronic noses  

NASA Astrophysics Data System (ADS)

A route for generating arrays of printable polythiophene-based gas sensor materials suitable for low-cost manufacturing is demonstrated. Materials with complementary sensor responses are synthesized by incorporating functional groups into the molecule, either along the polymer backbone or as end-capping groups. Using these materials as printable sensor inks, a functional, integrated gas sensor array chip is fabricated using additive deposition techniques. The sensor array shows sensitivity to a range of volatile organic compounds down to concentrations of 10ppm. A three-terminal thin film transistor structure is used, allowing the extraction of multiple parameters that help to elucidate the mechanisms responsible for sensor response and the role of the functional groups in this response.

Chang, Josephine B.; Liu, Vincent; Subramanian, Vivek; Sivula, Kevin; Luscombe, Christine; Murphy, Amanda; Liu, Jinsong; Fréchet, Jean M. J.

2006-07-01

183

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

184

CSA doped polypyrrole-zinc oxide thin film sensor  

NASA Astrophysics Data System (ADS)

The polypyrrole-zinc oxide (PPy-ZnO) hybrid sensor doped with different weight ratios of camphor sulphonic acid (CSA) were prepared by spin coating technique. These CSA doped PPy-ZnO hybrids were characterized by field emission scanning electron microscope (FESEM) and fourier transform infrared (FTIR) which proved the formation of polypyrrole, PPy-ZnO and the interaction between polypyrrole - ZnO (PPy-ZnO) hybrid with CSA doping. The gas sensing properties of the PPy-ZnO hybrid films doped with CSA have been studied for oxidizing (NO2) as well as reducing (H2S, NH3, CH4OH and CH3OH) gases at room temperature. We demonstrate that CSA doped PPy-ZnO hybrid films are highly selective to NO2 along with high-sensitivity at low concentration (80% to 100 ppm) and better stability, which suggested that the CSA doped PPy-ZnO hybrid films are potential candidate for NO2 detection at room temperature.

Chougule, M. A.; Jundale, D. M.; Raut, B. T.; Sen, Shashwati; Patil, V. B.

2013-02-01

185

Platinum thin film resistors as accurate and stable temperature sensors  

NASA Technical Reports Server (NTRS)

The measurement characteristics of thin-Pt-film temperature sensors fabricated using advanced methods are discussed. The limitations of wound-wire Pt temperature sensors and the history of Pt-film development are outlined, and the commonly used film-deposition, structuring, and trimming methods are presented in a table. The development of a family of sputtered film resistors is described in detail and illustrated with photographs of the different types. The most commonly used tolerances are reported as + or - 0.3 C + 0.5 percent of the temperature measured.

Diehl, W.

1984-01-01

186

Nanostructure Engineered Chemical Sensors for Hazardous Gas and Vapor Detection  

NASA Technical Reports Server (NTRS)

A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs) and metal oxides nanowires or nanobelts, on a pair of interdigitated electrodes (IDE) processed with a silicon based microfabrication and micromachining technique. The IDE fingers were fabricated using thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to hazardous gases and vapors, such as acetone, benzene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing in our sensor platform can be understood by electron modulation between the nanostructure engineered device and gas molecules. As a result of the electron modulation, the conductance of nanodevice will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost.

Li, Jing; Lu, Yijiang

2005-01-01

187

Surface acoustic wave ammonia sensor based on ZnO/SiO2 composite film.  

PubMed

A surface acoustic wave (SAW) resonator with ZnO/SiO2 (ZS) composite film was used as an ammonia sensor in this study. ZS composite films were deposited on the surface of SAW devices using the sol-gel method, and were characterized using SEM, AFM, and XRD. The performance of the sensors under ammonia gas was optimized by adjusting the molar ratio of ZnO:SiO2 to 1:1, 1:2 and 1:3, and the sensor with the ratio of ZnO to SiO2 equaling to 1:2 was found to have the best performance. The response of sensor was 1.132 kHz under 10 ppm NH3, which was much higher than that of the sensor based on a pristine ZnO film. Moreover, the sensor has good selectivity, reversibility and stability at room temperature. These can be attributed to the enhanced absorption of ammonia and unique surface reaction on composite films due to the existence of silica. PMID:25528236

Wang, Shuang-Yue; Ma, Jin-Yi; Li, Zhi-Jie; Su, H Q; Alkurd, N R; Zhou, Wei-Lie; Wang, Lu; Du, Bo; Tang, Yong-Liang; Ao, Dong-Yi; Zhang, Shou-Chao; Yu, Q K; Zu, Xiao-Tao

2015-03-21

188

Pattern Recognition Techniques for Odor Discrimination in Gas Sensor Array  

E-print Network

sensors for the detection of single gases (such as CO, CH4, H2, SO2, NOx, O3 etc...) has seenPattern Recognition Techniques for Odor Discrimination in Gas Sensor Array Amine Bermak, Sofiane of the most recent as well as tradi- tional applications for gas sensors. The table also reports the gases

Martinez, Dominique

189

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

190

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

191

Low-Cost Hydrogen Sulfide Gas Sensor on Paper Substrates: Fabrication and Demonstration  

Microsoft Academic Search

Drop-cast deprotonated emeraldine base (poly)aniline (PANI)—copper chloride films on paper substrates containing ink-jet printed silver electrodes have been prepared and are shown to be promising low-cost gas-sensors for ${\\\\rm H}_{2}{\\\\rm S}$ at room temperature. These films showed large changes in the conductivity (three to four orders of magnitude) upon exposure to low concentrations of ${\\\\rm H}_{2}{\\\\rm S}$ (10 ppm) due

Jawad Sarfraz; Daniel Tobjork; Ronald Osterbacka; Mika Linden

2012-01-01

192

Tailoring of sol-gel films for optical sensing of oxygen in gas and aqueous phase.  

PubMed

Sol-gel-based optical sensors for both gas-phase and dissolved oxygen have been developed. Both sensors operate on the principle of fluorescence quenching of a ruthenium complex which has been entrapped in a porous sol-gel silica film. A comprehensive investigation was carried out in order to establish optimal film-processing parameters for the two sensing environments. Both tetraethoxysilane and organically modified sol-gel precursors such as methyltriethoxysilane and ethyltriethoxysilane were used. Film hydrophobicity increases as a function of modified precursor content, and this was correlated with enhanced dissolved oxygen (DO) sensor performance. Extending the aliphatic group of the modified precursor further improved DO sensitivity. The influence of water/precursor molar ratio, R, on the sol-gel film microstructure was investigated. R value tailoring of the microstructure and film surface hydrophobicity tailoring were correlated with oxygen diffusion behavior in the films via the Stern-Volmer constants for both gas phase and DO sensing. Excellent performance characteristics were measured for both gas-phase and DO oxygen sensors. The long-term quenching stability of DO sensing films was established over a period of 6 months. PMID:21644598

McDonagh, C; Maccraith, B D; McEvoy, A K

1998-01-01

193

ADVANCES IN THIN FILM SENSOR TECHNOLOGIES FOR ENGINE APPLICATIONS  

Microsoft Academic Search

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)

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

194

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

195

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

196

New method for selectivity enhancement of SiC field effect gas sensors for quantification of NOx  

Microsoft Academic Search

A Silicon Carbide based enhancement type field effect transistor with porous films of Iridium and Platinum as gate metallization has been investigated as a total NOx sensor operated in a temperature cycling mode. This operating mode is quite new for gas sensors based on the field effect but promising results have been reported earlier. Based on static investigations we have

Christian Bur; Peter Reimann; Mike Andersson; Anita Lloyd Spetz; Andreas Schütze

2011-01-01

197

A Novel "Green" Fully-integrated Ultrasensitive RFID-enabled Gas Sensor Utilizing Inkjet-printed Antennas and Carbon Nanotubes  

E-print Network

A Novel "Green" Fully-integrated Ultrasensitive RFID-enabled Gas Sensor Utilizing Inkjet Institute ofTechnology, Atlanta, GA, 30332, U.S.A. Abstract In this paper, the integration of a flexible RFID tag with an inkjet-printed Single Walled Carbon Nanotube (SWCNT) film in a chipless sensor node

Tentzeris, Manos

198

Sensors employing Functionalized Conducting Polymer Thin Film Transistors  

NASA Astrophysics Data System (ADS)

Functionalized conducting polymers are employed as active layers in sensors with a thin film transistor (TFT) device structure. Such devices can work as multi-parameter sensors with responses that are fast, repeatable and reversible at room temperature. In this work, a strategy is proposed to enhance the chemical selectivity of organic TFT sensors, by selecting active layers that are made of conducting polymers bearing chemically different substituents. A modulation of the devices sensitivity towards analytes such as alcohols and ketones is demonstrated.

Tanese, M. C.; Torsi, L.; Cioffi, N.; Sabbatini, L.; Zambonin, P. G.

2003-12-01

199

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

200

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.

2012-06-01

201

A thick-film pyroelectric PLZT ceramic sensor  

Microsoft Academic Search

A thick-film preparation method and examples of the action of a pyroelectric lead lanthanum zirconate titanate (PLZT) thick-film sensor are described. Ceramic powders for thick-film PLZT paste production are prepared by a chemical method, starting with lead oxide, solutions of zirconium oxynitrate and lanthanum nitrate and titanium dioxide complexed with hydrogen peroxide. A PLZT 12\\/40\\/60 powder composition is used. A

S. Leppävuori; A. H. ?ozi?ski; A. Uusimaki

1995-01-01

202

SnO2 Highly Sensitive CO Gas Sensor Based on Quasi-Molecular-Imprinting Mechanism Design.  

PubMed

Response of highly sensitive SnO2 semiconductor carbon monoxide (CO) gas sensors based on target gas CO quasi-molecular-imprinting mechanism design is investigated with gas concentrations varied from 50 to 3000 ppm. SnO2 nanoparticles prepared via hydrothermal method and gas sensor film devices SC (exposed to the target gas CO for 12 h after the suspension coating of SnO2 film to be fully dried, design of quasi-molecular-imprinting mechanism, the experiment group) and SA (exposed to air after the suspension coating of SnO2 film to be fully dried, the comparison group) made from SnO2 nanoparticles are all characterized by XRD, SEM and BET surface area techniques, respectively. The gas response experimental results reveal that the sensor SC demonstrates quicker response and higher sensitivity than the sensor SA does. The results suggest that in addition to the transformation of gas sensor materials, surface area, and porous membrane devices, the Molecular Imprinting Theory is proved to be another way to promote the performance of gas sensors. PMID:25664435

Li, Chenjia; Lv, Meng; Zuo, Jialin; Huang, Xintang

2015-01-01

203

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

204

A pressurized gas squeeze film journal damper  

NASA Technical Reports Server (NTRS)

A lumped parameter model is developed to determine the stiffness and damping characteristics of inherently compensated gas film bearings. The model relies on the average static pressure over a one dimensional strip bearing. Results of the model are compared with known computer solutions for the distributed strip and a two dimensional square bearing. The results for the stiffness agree well with the computer solutions although the model proved to be inadequate for predicting the film damping.

Stiffler, A. K.

1977-01-01

205

High-sensitivity sensor design based on cascaded long-period fiber grating with film coating  

NASA Astrophysics Data System (ADS)

A cascaded long-period fiber grating (CLPFG) sensor with film coating is presented. Two long-period fiber gratings (LPFGs) are cascaded to form a Mach-Zehnder interferometer. The optical transmission spectrum and the sensing characteristics for ambient refractive index (RI) measurement of the CLPFG sensor are analyzed in a form of transfer matrix based on rigorous coupled-mode theory. The results indicate that it is highly sensitive to the film RI and surrounding RI, so it can be used as a gas sensor or a solution sensor. Data simulation shows that the resolution of the RI of the films is predicted to be 10-7. Further, a cascaded chirped LPFG is introduced to study its sensing performance. The influence of the chirp coefficient and the grating structural parameters on the transmission spectrum of the cascaded chirped LPFG is analyzed. Data simulation shows that the resolution of the RI of the films is predicted to be 10-9. In contrast to the conventional measurement method based on interrogating the wavelength change, intensity detection of this cascaded chirped LPFG sensor means that no optical spectrum analyzer is required in the measuring system, which is favorable for practical applications, especially for in situ environmental motoring.

Gu, Zhengtian; Jiang, Xiuli; Chen, Haiyun

2014-02-01

206

Comparative studies on polymer coated SAW and STW resonators for chemical gas sensor applications  

Microsoft Academic Search

This paper presents and compares experimental data from performance tests on polymer coated 433 MHz surface acoustic wave (SAW) and 1 GHz surface transverse wave (STW) based two-port resonators for chemical gas sensor applications. The acoustic devices were coated with gas sensitive polymer films of different thickness' and viscoelastic properties as parylene C, poly-(2-hydroxyethylmethacrylate) (PHEMA) and poly-(n-butyl-methacrylate) (PBMA). Then they

I. D. Avramov; M. Rapp; A. Voigt; U. Stahl; M. Dirschka

2000-01-01

207

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

208

A Micro-Fabricated Force Sensor Using an All Thin Film Piezoelectric Active Sensor  

PubMed Central

The ability to measure pressure and force is essential in biomedical applications such as minimally invasive surgery (MIS) and palpation for detecting cancer cysts. Here, we report a force sensor for measuring a shear and normal force by combining an arrayed piezoelectric sensors layer with a precut glass top plate connected by four stress concentrating legs. We designed and fabricated a thin film piezoelectric force sensor and proposed an enhanced sensing tool to be used for analyzing gentle touches without the external voltage source used in FET sensors. Both the linear sensor response from 3 kPa to 30 kPa and the exact signal responses from the moving direction illustrate the strong feasibility of the described thin film miniaturized piezoelectric force sensor. PMID:25429407

Lee, Junwoo; Choi, Wook; Yoo, Yong Kyoung; Hwang, Kyo Seon; Lee, Sang-Myung; Kang, Sungchul; Kim, Jinseok; Lee, Jeong Hoon

2014-01-01

209

Electrothermal modeling of a microbridge gas sensor  

NASA Astrophysics Data System (ADS)

Fully CMOS-compatible, surface-micromachined polysilicon microbridges have ben designed, fabricated, and tested for use in catalytic, calorimetric gas sensing. To improve sensor behavior, extensive electro-thermal modeling efforts were undertaken using SPICE. The validity of the SPICE model was verified by comparing its simulated behavior with experimental results. The temperature distribution of an electrically-heated microbridge was measured using an IR microscope. Comparisons among the measured distribution, the SPICE simulation, and distributions obtained by analytical methods show that heating at the ends of a microbridge has important implications for device response. Additional comparisons between measured and simulated current-voltage characteristics, as well as transient response characteristics, further support the accuracy of the model. A major benefit of electro-thermal modeling with SPICE is the ability to simultaneously simulate the behavior of a device and its control/sensing electronics. Results for the combination of a unique constant-resistance control circuit and microbridge gas sensor ar given. Models of in situ techniques for monitoring catalyst deposition are shown to be in agreement with experiment. Finally, simulated chemical response of the detector is compared with the data, and methods of improving response through modifications in bridge geometry are predicted.

Manginell, Ronald P.; Smith, James H.; Ricco, Antonio J.; Hughes, Robert C.; Moreno, Daniel J.; Huber, Robert J.

1997-09-01

210

Miniature infrared gas sensors using photonic crystals  

NASA Astrophysics Data System (ADS)

We present an optical gas sensor based on the classical nondispersive infrared technique using ultracompact photonic crystal gas cells. The ultracompact device is conceptually based on low group velocities inside a photonic crystal gas cell and low-reflectivity antireflection layers coupling light into the device. Experimentally, an enhancement of the CO2 infrared absorption by a factor of 2.6 to 3.5 as compared to an empty cell, due to slow light inside a 2D silicon photonic crystal gas cell, was observed; this is in excellent agreement with numerical simulations. We show that, theoretically, for an optimal design enhancement factors of up to 60 are possible in the region of slow light. However, the overall transmission of bulk photonic crystals, and thus the performance of the device, is limited by fluctuations of the pore diameter. Numerical estimates suggest that the positional variations and pore diameter fluctuations have to be well below 0.5% to allow for a reasonable transmission of a 1 mm device.

Pergande, Daniel; Geppert, Torsten M.; Rhein, Andreas von; Schweizer, Stefan L.; Wehrspohn, Ralf B.; Moretton, Susanne; Lambrecht, Armin

2011-04-01

211

Fabrication of a SnO2-based acetone gas sensor enhanced by molecular imprinting.  

PubMed

This work presents a new route to design a highly sensitive SnO2-based sensor for acetone gas enhanced by the molecular imprinting technique. Unassisted and acetone-assisted thermal synthesis methods are used to synthesis SnO2 nanomaterials. The prepared SnO2 nanomaterials have been characterized by X-ray powder diffraction, scanning electron microscopy and N2 adsorption-desorption. Four types of SnO2 films were obtained by mixing pure deionized water and liquid acetone with the two types of as-prepared powders, respectively. The acetone gas sensing properties of sensors coated by these films were evaluated. Testing results reveal that the sensor coated by the film fabricated by mixing liquid acetone with the SnO2 nanomaterial synthesized by the acetone-assisted thermal method exhibits the best acetone gas sensing performance. The sensor is optimized for the smooth adsorption and desorption of acetone gas thanks to the participation of acetone both in the procedure of synthesis of the SnO2 nanomaterial and the device fabrication, which results in a distinct response-recovery behavior. PMID:25549174

Tan, Wenhu; Ruan, Xiaofan; Yu, Qiuxiang; Yu, Zetai; Huang, Xintang

2015-01-01

212

Fabrication of a SnO2-Based Acetone Gas Sensor Enhanced by Molecular Imprinting  

PubMed Central

This work presents a new route to design a highly sensitive SnO2–based sensor for acetone gas enhanced by the molecular imprinting technique. Unassisted and acetone-assisted thermal synthesis methods are used to synthesis SnO2 nanomaterials. The prepared SnO2 nanomaterials have been characterized by X-ray powder diffraction, scanning electron microscopy and N2 adsorption?desorption. Four types of SnO2 films were obtained by mixing pure deionized water and liquid acetone with the two types of as-prepared powders, respectively. The acetone gas sensing properties of sensors coated by these films were evaluated. Testing results reveal that the sensor coated by the film fabricated by mixing liquid acetone with the SnO2 nanomaterial synthesized by the acetone-assisted thermal method exhibits the best acetone gas sensing performance. The sensor is optimized for the smooth adsorption and desorption of acetone gas thanks to the participation of acetone both in the procedure of synthesis of the SnO2 nanomaterial and the device fabrication, which results in a distinct response–recovery behavior. PMID:25549174

Tan, Wenhu; Ruan, Xiaofan; Yu, Qiuxiang; Yu, Zetai; Huang, Xintang

2015-01-01

213

Chemoresistive Gas Sensors for the Detection of Colorectal Cancer Biomarkers  

PubMed Central

Numerous medical studies show that tumor growth is accompanied by protein changes that may lead to the peroxidation of the cell membrane with consequent emission of volatile organic compounds (VOCs) by breath or intestinal gases that should be seen as biomarkers for colorectal cancer (CRC). The analysis of VOCs represents a non-invasive and potentially inexpensive preliminary screening technique. An array of chemoresistive gas sensors based on screen-printed metal oxide semiconducting films has been selected to discriminate gases of oncological interest, e.g., 1-iodononane and benzene, widely assumed to be biomarkers of colorectal cancer, from those of interference in the gut, such as methane and nitric oxide. PMID:25313496

Malagù, Cesare; Fabbri, Barbara; Gherardi, Sandro; Giberti, Alessio; Guidi, Vincenzo; Landini, Nicolò; Zonta, Giulia

2014-01-01

214

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

215

Preparation of the spacer for narrow electrode gap configuration in ionization-based gas sensor  

SciTech Connect

Carbon nanotubes (CNTs) have started to be developed as the sensing element for ionization-based gas sensors due to the demand for improved sensitivity, selectivity, stability and other sensing properties beyond what can be offered by the conventional ones. Although these limitations have been overcome, the problems still remain with the conventional ionization-based gas sensors in that they are bulky and operating with large breakdown voltage and high temperature. Recent studies have shown that the breakdown voltage can be reduced by using nanostructured electrodes and narrow electrode gap. Nanostructured electrode in the form of aligned CNTs array with evenly distributed nanotips can enhance the linear electric field significantly. The later is attributed to the shorter conductivity path through narrow electrode gap. The paper presents the study on the design consideration in order to realize ionization based gas sensor using aligned carbon nanotubes array in an optimum sensor configuration with narrow electrode gap. Several deposition techniques were studied to deposit the spacer, the key component that can control the electrode gap. Plasma spray deposition, electron beam deposition and dry oxidation method were employed to obtain minimum film thickness around 32 {mu}m. For plasma spray method, sand blasting process is required in order to produce rough surface for strong bonding of the deposited film onto the surface. Film thickness, typically about 39 {mu}m can be obtained. For the electron beam deposition and dry oxidation, the film thickness is in the range of nanometers and thus unsuitable to produce the spacer. The deposited multilayer film consisting of copper, alumina and ferum on which CNTs array will be grown was found to be removed during the etching process. This is attributed to the high etching rate on the thin film which can be prevented by reducing the rate and having a thicker conductive copper film.

Saheed, Mohamed Shuaib Mohamed; Mohamed, Norani Muti; Burhanudin, Zainal Arif [Electrical and Electronic Engineering, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak. (Malaysia); Fundamental and Applied Science, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak. (Malaysia); Electrical and Electronic Engineering, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak. (Malaysia)

2012-09-26

216

Fast Solid State Gas Sensor Characterization Ruby N. Ghosh1  

E-print Network

Fluorescence (LIF) imaging. The sensor is char- acterized under standard industrial sensor operating conditions of air and fuel in an internal combustion engine and the detec- tion of flame fronts in controlled. The sensor is mounted face down. In the "moving part", the two gas jets are separated by a thin barrier

Hu, Hui

217

Recent Progress in Electrochemical Gas Sensors Based on Solid Electrolytes  

Microsoft Academic Search

In recent years, highly sensitive and selective detection of various gases has become increasingly important especially for the purpose of emission control and atmospheric environmental monitoring. Up to date, various electrochemical gas sensors based on solid electrolytes have been developed or proposed. The importance of solid electrolyte sensors was strongly recognized at an early stage when potentiometric zirconia-based oxygen sensors

Norio Miura

2002-01-01

218

Gas sensor arrays for quantitative analysis and alarm generation  

Microsoft Academic Search

The use of different approaches for analysing the response of a small sensor array based on artificial neural networks is presented. In one case the quantification of all compounds in a three component mixture is discussed. Based on the same gas sensor array (and data) an approach for extracting safety information directly from the sensor array response is illustrated. Carbon

G. Huyberechts; P. M. Szecowka; B. W. Licznerski

1997-01-01

219

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

220

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

221

21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.  

Code of Federal Regulations, 2013 CFR

...false Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section...4410 Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that...

2013-04-01

222

21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.  

Code of Federal Regulations, 2014 CFR

...false Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section...4410 Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that...

2014-04-01

223

21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.  

Code of Federal Regulations, 2012 CFR

...false Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section...4410 Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that...

2012-04-01

224

21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.  

Code of Federal Regulations, 2010 CFR

...false Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section...4410 Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that...

2010-04-01

225

21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.  

Code of Federal Regulations, 2011 CFR

...false Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section...4410 Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that...

2011-04-01

226

Isolating Gas Sensor From Pressure And Temperature Effects  

NASA Technical Reports Server (NTRS)

Two-stage flow system enables oxygen sensor in system to measure oxygen content of low-pressure, possibly-high-temperature atmosphere in test environment while protecting sensor against possibly high temperature and fluctuations in pressure of atmosphere. Sensor for which flow system designed is zirconium oxide oxygen sensor sampling atmospheres in high-temperature wind tunnels. Also adapted to other gas-analysis instruments that must be isolated from pressure and temperature effects of test environments.

Sprinkle, Danny R.; Chen, Tony T. D.; Chaturvedi, Sushi K.

1994-01-01

227

A film pressure sensor based on optical fiber Bragg grating  

NASA Astrophysics Data System (ADS)

The measurement of pressure is essential for the design and flying controlling of aircraft. In order to measure the surface pressures of the aircraft, the common pressure tube method and Pressure sensitive paint measurement method have their own disadvantages, and are not applicable to all aircraft structures and real time pressure monitoring. In this paper, a novel thin film pressure sensor based on Fiber Bragg Grating (FBG) is proposed, using FBG measuring the tangential strain of the disk sensing film. Theoretical circle strain of the disk sensing film of the pressure sensor under pressure and temperature variation are analyzed, and the linear relationship between FBG center wavelength shift and pressure, temperature variation is gotten. The pressure and temperature calibration experiments prove the theoretical analysis. But the calibration sensing parameters are small than the calculating ones, which is caused by the constraint of optical fibre to the thin sensing film.

Zhang, Zhichun; Deng, Gang; Dai, Yongbo; Liu, Yanju; Leng, Jinsong

2010-03-01

228

Ultrasensitive thin film infrared sensors enabled by hybrid nanomaterials.  

PubMed

IR sensing is an important technology with applications in renewable energy, environmental science and medical engineering. Herein environment-friendly IR sensors based on the single-walled carbon nanotube-copper sulfide nanoparticle (SWNT-CuS NP) hybrid nanomaterials are reported. The IR response in the photocurrent of a SWNT-CuS NP hybrid thin-film sensor is significantly enhanced when the IR light illuminates the thin-film device asymmetrically. We show that the change of photocurrent is up to 300%, which is 10× to 100× larger than those of other reported nanomaterial-based IR sensors. The detection limit can be as low as 48 ?W mm(-2), among the lowest of the previously reported IR nanosensors. The dramatically enhanced sensitivity and detection limit are due to the temperature difference between the two junctions formed by the nanohybrid thin film and Cu-wire electrodes under asymmetric IR illumination, and the difference between the effective Seebeck coefficient of the nanohybrid thin film and that of the Cu wire. The IR sensor embedded in polydimethylsiloxane (PDMS) layers has been fabricated and tested, indicating its potential application as a flexible IR sensor. PMID:23579239

Tseng, Yi-Hsuan; He, Yuan; Que, Long

2013-05-21

229

Design of Intelligent Optical Sensors with Organized Bacteriorhodopsin Films  

NASA Astrophysics Data System (ADS)

Oriented purple membrane (PM) films comprised of the photosensitive retinal protein bacteriorhodopsin (bR) was immobilized in an electrochemical photocell by means of bioaffinity bonding with bispecific (BS) anitibodies that recognize bR. Charge displacement photocurrent of significant efficiency was obtained from the homogeneously oriented PM film. Based on this technology, methods are described for the design of intelligent optoelectronic devices, which include image sensors for motion sensing, photoreceptor tips for visual prosthesis of human eyes, and environmental sensors for use in direction sensing and speed sensing.

Miyasaka, Tsutomu

1995-07-01

230

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

231

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. PMID:22294916

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

2010-01-01

232

Thin film stress measurement by instrumented optical fibre displacement sensor  

NASA Astrophysics Data System (ADS)

Residual stress can adversely affect the mechanical, electronic, optical and magnetic properties of thin films. This work describes a simple stress measurement instrument based on the bending beam method together with a sensitive non-contact fibre optical displacement sensor. The fibre optical displacement sensor is interfaced to a computer and a Labview programme enables film stress to be determined from changes in the radius of curvature of the film-substrate system. The stress measurement instrument was tested for two different kinds of thin film, hard amorphous carbon nitride (CN) and soft copper (Cu) films on silicon substrates deposited by RF magnetron sputtering. Residual stress developed in 500 nm thick CN thin films deposited at substrate temperatures in the range 50-550 °C was examined and it was found that stress in CN films decreased from 0.83 to 0.44 GPa compressive with increase of substrate temperature. Residual stress was found to be tensile (121 MPa) for Cu films of thickness 1500 nm deposited at room temperature.

Chowdhury, S.; Laugier, M. T.

2007-02-01

233

Development of SiC Gas Sensor Systems  

NASA Astrophysics Data System (ADS)

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.

2002-10-01

234

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

235

Study of quartz crystal microbalance NO2 sensor coated with sputtered indium tin oxide film  

NASA Astrophysics Data System (ADS)

A study of NO2 gas sorption ability of thin indium tin oxide (ITO) deposited on 16 MHz quartz crystal microbalance (QCM) is presented. ITO films are grown by RF sputtering of indium/tin target with weight proportion 95:5 in oxygen environment. The ITO films have been characterized by X-ray photoelectron spectroscopy measurements. The ITO surface composition in atomic % is defined to be: In-40.6%, Sn-4.3% and O-55%. The thickness and refractive index of the films are determined by ellipsometric method. The frequency shift of QCM-ITO is measured at different NO2 concentrations. The QCM-ITO system becomes sensitive at NO2 concentration >= 500 ppm. The sorbed mass for each concentration is calculated according the Sauerbrey equation. The results indicated that the 1.09 ng of the gas is sorbed into 150 nm thick ITO film at 500 ppm NO2 concentration. When the NO2 concentration increases 10 times the calculated loaded mass is 5.46 ng. The sorption process of the gas molecules is defined as reversible. The velocity of sorbtion /desorption processes are studied, too. The QCM coated with thin ITO films can be successfully used as gas sensors for detecting NO2 in the air at room temperature.

Georgieva, V.; Aleksandrova, M.; Stefanov, P.; Grechnikov, A.; Gadjanova, V.; Dilova, T.; Angelov, Ts

2014-12-01

236

Sensors and Actuators B, 2 (1990) 19-81 79 Photopyroelectric (P'E) Sensor for Trace Hydrogen Gas Detection  

E-print Network

research effort has been directed toward the development of hydrogen gas sensors. A number of gas sensorsSensors and Actuators B, 2 (1990) 19-81 79 Photopyroelectric (P'E) Sensor for Trace Hydrogen Gas, Department of Mechanical Engineering, and Center for Hydrogen and Electrochemical Studies (CHES), University

Mandelis, Andreas

237

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. 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

238

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

239

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

240

Design and deployment of low-cost plastic optical fiber sensors for gas monitoring.  

PubMed

This paper describes an approach to develop and deploy low-cost plastic optical fiber sensors suitable for measuring low concentrations of pollutants in the atmosphere. The sensors are designed by depositing onto the exposed core of a plastic fiber thin films of sensitive compounds via either plasma sputtering or via plasma-enhanced chemical vapor deposition (PECVD). The interaction between the deposited layer and the gas alters the fiber's capability to transmit the light, so that the sensor can simply be realized with a few centimeters of fiber, an LED and a photodiode. Sensors arranged in this way exhibit several advantages in comparison to electrochemical and optical conventional sensors; in particular, they have an extremely low cost and can be easily designed to have an integral, i.e., cumulative, response. The paper describes the sensor design, the preparation procedure and two examples of sensor prototypes that exploit a cumulative response. One sensor is designed for monitoring indoor atmospheres for cultural heritage applications and the other for detecting the presence of particular gas species inside the RPC (resistive plate chamber) muon detector of the Compact Muon Solenoid (CMS) experiment at CERN in Geneva. PMID:25558990

Grassini, Sabrina; Ishtaiwi, Maen; Parvis, Marco; Vallan, Alberto

2015-01-01

241

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

242

Fiber-Optic Sensor Would Monitor Growth of Polymer Film  

NASA Technical Reports Server (NTRS)

A proposed optoelectronic sensor system would measure the increase in thickness of a film of parylene (a thermoplastic polymer made from para-xylene) during growth of the film in a vapor deposition process. By enabling real-time monitoring of film thickness, the system would make it possible to identify process conditions favorable for growth and to tailor the final thickness of the film with greater precision than is now possible. The heart of the sensor would be a pair of fiber-optic Fabry-Perot interferometers, depicted schematically in the figure. (In principle, a single such interferometer would suffice. The proposal calls for the use of two interferometers for protective redundancy and increased accuracy.) Each interferometer would include a light source, a fiber-optic coupler, and photodetectors in a control box outside the deposition chamber. A single-mode optical fiber for each interferometer would run from inside the control box to a fused-silica faceplate in a sensor head. The sensory tips of the optical fibers would be polished flush with the free surface of the faceplate. In preparation for use, the sensor head would be mounted with a hermetic seal in a feed-through port in the deposition chamber, such that free face of the faceplate and the sensory tips of the optical fibers would be exposed to the deposition environment. During operation, light would travel along each optical fiber from the control box to the sensor head. A small portion of the light would be reflected toward the control box from the end face of each fiber. Once growth of the parylene film started, a small portion of the light would also be reflected toward the control box from the outer surface of the film. In the control box, the two reflected portions of the light beam would interfere in one of the photodetectors. The difference between the phases of the interfering reflected portions of the light beam would vary in proportion to the increasing thickness of the film and the known index of refraction of the film, causing the photodetector reading to vary in proportion to a known sinusoidal function of film thickness. Electronic means of monitoring this variation and the corresponding variation in phase and thickness are well established in the art of interferometry. Hence, by tracking the cumulative change in phase difference from the beginning of deposition, one could track the growing thickness of the film to within a small fraction of a wavelength of light.

Beamesderfer, Michael

2005-01-01

243

Gas-film coefficients for streams  

USGS Publications Warehouse

Equations for predicting the gas-film coefficient for the volatilization of organic solutes from streams are developed. The film coefficient is a function of windspeed and water temperature. The dependence of the coefficient on windspeed is determined from published information on the evaporation of water from a canal. The dependence of the coefficient on temperature is determined from laboratory studies on the evaporation of water. Procedures for adjusting the coefficients for different organic solutes are based on the molecular diffusion coefficient and the molecular weight. The molecular weight procedure is easiest to use because of the availability of molecular weights. However, the theoretical basis of the procedure is questionable. The diffusion coefficient procedure is supported by considerable data. Questions, however, remain regarding the exact dependence of the film coefficint on the diffusion coefficient. It is suggested that the diffusion coefficient procedure with a 0.68-power dependence be used when precise estimate of the gas-film coefficient are needed and that the molecular weight procedure be used when only approximate estimates are needed.

Rathbun, R.E.; Tai, D.Y.

1983-01-01

244

Ultralow drift in organic thin-film transistor chemical sensors by pulsed gating  

E-print Network

Ultralow drift in organic thin-film transistor chemical sensors by pulsed gating Richard D. Yang the baseline stability of organic thin-film transistor OTFT chemical sensors. Trap states in the organic films of Physics. DOI: 10.1063/1.2767633 I. INTRODUCTION Organic thin-film transistors OTFTs have been investi

Kummel, Andrew C.

245

Designing an amperometric thick-film microbial BOD sensor  

Microsoft Academic Search

Thick film oxygen electrodes manufactured by screen print method have been used as a transducer for a biochemical oxygen demand (BOD) sensor. The kinetics of the immobilized yeast, Arxula adeninivorans (Arxula) has been studied. The apparent KM of immobilized Arxula (>100 ?M) is higher than free cells of Arxula (70 ?M). The increase in KM caused by the effect of

Chiyui Chan; Matthias Lehmann; Kinman Chan; Puiyee Chan; Chiwai Chan; Bernd Gruendig; Gotthard Kunze; Reinhard Renneberg

2000-01-01

246

Thin Film Heat Flux Sensor of Improved Design  

NASA Technical Reports Server (NTRS)

A new design for a thin film heat flux sensor is presented. It is easier to fabricate than previous designs, for a given heat flux has an order of magnitude larger signal, and is more easily scalable than previous designs. Transient and steady state data are also presented.

Fralick, Gus; Wrbanek, John; Blaha, Charles

2002-01-01

247

Waveguide Zeeman interferometry for thin-film chemical sensors  

SciTech Connect

A chemical sensor is demonstrated which is based on Si{sub 3}N{sub 4} optical waveguides coated with species-selective thin films and using Zeeman interferometry as the detection technique. Relative phase change between TE and TM modes is measured. Real time and reversible response to toluene is shown with ppm level sensitivity.

Grace, K.M.; Shrouf, K.; Johnston, R.G.; Yang, X.; Swanson, B. [Los Alamos National Lab., NM (United States); Honkanen, S.; Ayras, P.; Peyghambarian, N. [Optical Sciences Center, Univ. of Arizona, Tucson, AZ (United States); Katila, P.; Leppihalme, M. [VTT Electronics (Finland)

1997-10-01

248

Detecting mustard gas using high Q-value SAW resonator gas sensors  

Microsoft Academic Search

Surface acoustic wave (SAW) resonator gas sensors have been applied in many fields for the advantages of high Q-value and low insertion loss, but seldom used in chemical warfare agents detection. In this paper, a novel SAW gas sensor with high Q-value for mustard gas (HD, a blister agent) detection was developed. The sensor was a two-port SAW resonator device

Chuan-zhi Chen; Bo-li Zuo; Jin-yi Ma; Hong-min Jiang

2008-01-01

249

Flexible PZT thin film tactile sensor for biomedical monitoring.  

PubMed

This paper presents the development of tactile sensors using the sol-gel process to deposit a PZT thin-film from 250 nm to 1 ?m on a flexible stainless steel substrate. The PZT thin-film tactile sensor can be used to measure human pulses from several areas, including carotid, brachial, finger, ankle, radial artery, and the apical region. Flexible PZT tactile sensors can overcome the diverse topology of various human regions and sense the corresponding signals from human bodies. The measured arterial pulse waveform can be used to diagnose hypertension and cardiac failure in patients. The proposed sensors have several advantages, such as flexibility, reliability, high strain, low cost, simple fabrication, and low temperature processing. The PZT thin-film deposition process includes a pyrolysis process at 150 °C/500 °C for 10/5 min, followed by an annealing process at 650 °C for 10 min. Finally, the consistent pulse wave velocity (PWV) was demonstrated based on human pulse measurements from apical to radial, brachial to radial, and radial to ankle. It is characterized that the sensitivity of our PZT-based tactile sensor was approximately 0.798 mV/g. PMID:23698262

Tseng, Hong-Jie; Tian, Wei-Cheng; Wu, Wen-Jong

2013-01-01

250

Flexible PZT Thin Film Tactile Sensor for Biomedical Monitoring  

PubMed Central

This paper presents the development of tactile sensors using the sol-gel process to deposit a PZT thin-film from 250 nm to 1 ?m on a flexible stainless steel substrate. The PZT thin-film tactile sensor can be used to measure human pulses from several areas, including carotid, brachial, finger, ankle, radial artery, and the apical region. Flexible PZT tactile sensors can overcome the diverse topology of various human regions and sense the corresponding signals from human bodies. The measured arterial pulse waveform can be used to diagnose hypertension and cardiac failure in patients. The proposed sensors have several advantages, such as flexibility, reliability, high strain, low cost, simple fabrication, and low temperature processing. The PZT thin-film deposition process includes a pyrolysis process at 150 °C/500 °C for 10/5 min, followed by an annealing process at 650 °C for 10 min. Finally, the consistent pulse wave velocity (PWV) was demonstrated based on human pulse measurements from apical to radial, brachial to radial, and radial to ankle. It is characterized that the sensitivity of our PZT-based tactile sensor was approximately 0.798 mV/g. PMID:23698262

Tseng, Hong-Jie; Tian, Wei-Cheng; Wu, Wen-Jong

2013-01-01

251

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

252

Semiconductor metal oxide compounds based gas sensors: A literature review  

NASA Astrophysics Data System (ADS)

This paper gives a statistical view about important contributions and advances on semiconductor metal oxide (SMO) compounds based gas sensors developed to detect the air pollutants such as liquefied petroleum gas (LPG), H2S, NH3, CO2, acetone, ethanol, other volatile compounds and hazardous gases. Moreover, it is revealed that the alloy/composite made up of SMO gas sensors show better gas response than their counterpart single component gas sensors, i.e., they are found to enhance the 4S characteristics namely speed, sensitivity, selectivity and stability. Improvement of such types of sensors used for detection of various air pollutants, which are reported in last two decades, is highlighted herein.

Patil, Sunil Jagannath; Patil, Arun Vithal; Dighavkar, Chandrakant Govindrao; Thakare, Kashinath Shravan; Borase, Ratan Yadav; Nandre, Sachin Jayaram; Deshpande, Nishad Gopal; Ahire, Rajendra Ramdas

2015-02-01

253

Semiconductor metal oxide compounds based gas sensors: A literature review  

NASA Astrophysics Data System (ADS)

This paper gives a statistical view about important contributions and advances on semiconductor metal oxide (SMO) compounds based gas sensors developed to detect the air pollutants such as liquefied petroleum gas (LPG), H2S, NH3, CO2, acetone, ethanol, other volatile compounds and hazardous gases. Moreover, it is revealed that the alloy/composite made up of SMO gas sensors show better gas response than their counterpart single component gas sensors, i.e., they are found to enhance the 4S characteristics namely speed, sensitivity, selectivity and stability. Improvement of such types of sensors used for detection of various air pollutants, which are reported in last two decades, is highlighted herein.

Patil, Sunil Jagannath; Patil, Arun Vithal; Dighavkar, Chandrakant Govindrao; Thakare, Kashinath Shravan; Borase, Ratan Yadav; Nandre, Sachin Jayaram; Deshpande, Nishad Gopal; Ahire, Rajendra Ramdas

2015-03-01

254

Thermoelectric gas sensors of different catalyst oxides and heater metals  

NASA Astrophysics Data System (ADS)

Thermoelectric hydrogen sensors with different catalyst oxides, Pt-Al2O3 and Pt-CeO2 have been prepared, and their gas sensing properties are investigated in the air and N2 flow. In air, the relationship between the sensor output and the gas concentration is a linear indicating the combustion only depends on the gas concentration in air. In N2 atmosphere, where the oxygen gas content of N2 source cylinder is below the industrial standard of 50 ppm, the sensor output shows also a linear relationship with the gas concentration, but depressed signal level. The microheater of the thermoelectric sensor has been prepared by the co-sputtering of tungsten and platinum to enhance the high temperature stability. The temperature coefficients of the Pt-W alloy multilayer heater were lowered to a half of the level of Pt.

Shin, W.; Nishibori, M.; Izu, N.; Itoh, T.; Matsubara, I.; Watanabe, N.; Kasuga, T.

2011-10-01

255

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.

Fralick, Gustave C.; Wrbanek, John D.

2007-01-01

256

Room temperature magnetoresistive sensor based on thick films manganese perovskite  

NASA Astrophysics Data System (ADS)

La 2/3Sr 1/3MnO 3 perovskite (LSMO), which shows a ferromagnetic transition above room temperature, is a good candidate to be used as a magnetoresistive sensor. Magnetic and transport properties of granular LSMO have been studied. Different grain size and the use of metal/insulator composites have been explored in order to optimize the magnetoresistive response. LSMO ceramic powder have been used to prepare thick films on polycrystalline Al 2O 3 substrates by screen printing. The magnetoresistive response of the grown thick films is analyzed in the range of technical fields. It is shown, that under appropriate conditions, materials having field sensitivity high enough for some applications at room temperature can be obtained. A magnetic sensor has been developed in order to show the feasibility of this material as a low-cost magnetic sensor.

Balcells, Ll; Carrillo, A. E.; Martínez, B.; Sandiumenge, F.; Fontcuberta, J.

2000-11-01

257

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 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 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. 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 microfabricated gas sensor technology make this area of sensor development a field of significant interest.

Hunter, Gary W.; Chen, Liong-Yu; Neudeck, Phil G.; Knight, Dale; Liu, C. C.; Wu, Q. H.; Zhou, H. J.; Makel, Darby; Liu, M.; Rauch, W. A.

1998-01-01

258

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

259

Chemical Gas Sensors for Aeronautics and Space Applications III  

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 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 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. 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 microfabricated gas sensor technology make this area of sensor development a field of significant interest.

Hunter, G. W.; Neudeck, P. G.; Chen, L. Y.; Liu, C. C.; Wu, Q. H.; Sawayda, M. S.; Jin, Z.; Hammond, J.; Makel, D.; Liu, M.; Rauch, W. A.; Hall, G.

1999-01-01

260

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

261

Effect of deposition times on structure of Ga-doped ZnO thin films as humidity sensor  

SciTech Connect

Gallium doped zinc oxide (GZO) has good electrical property. It is widely used as transparent electrode in photovoltaic devices, and sensing element in gas and pressure sensors. GZO thin film was prepared using magnetron sputtering. Film deposition times were set at 10, 15, 20, 25 and 30 minutes to get samples of different thickness. X-ray diffraction (XRD) was used to determine the structure of GZO thin films. Structure for GZO thin film is hexagonal wurtzite structure. Morphology and thickness of GZO thin films was observed from FESEM micrographs. Grain size and thickness of thin films improved with increasing deposition times. However, increasing the thickness of thin films occur below 25 minutes only. Electrical properties of GZO thin films were studied using a four-point probe technique. The changes in the structure of the thin films lead to the changed of their electrical properties resulting in the reduction of the film resistance. These thin films properties significantly implying the potential application of the sample as a humidity sensor.

Khalid, Faridzatul Shahira; Awang, Rozidawati [School of Applied Physics, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

2014-09-03

262

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

263

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. PMID:24625742

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

2014-01-01

264

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

265

Elaboration and characterization of doped barium titanate films for gas sensing  

NASA Astrophysics Data System (ADS)

Barium titanate (BaTiO3) thick films were prepared from commercial powder to develop and optimize the film elaboration. Then, BaTiO3 was doped by strontium and iron to increase the conductivity by a double substitution on site A and B of the perovskite structure in view to develop semiconductor gas sensors. Film inks were prepared by mixing BT and BSTF powder with an organic vehicle, using a ratio of 50:50; 60:40, respectively and deposited on alumina substrates. The BT and BSTF films were sintered at 1100°C for 2h. The structural and physical properties of the films have been studied by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The dielectric measurements showed a huge increase in the a.c. conductivity for the BSTF films, by a factor of 10000 at low frequency, when the temperature ranges from 25°C to 500°C.

Romh, M. A. El; Fasquelle, D.; Députier, S.; Mascot, M.

2014-11-01

266

Bilayer functionally gradient thick film semiconducting methane sensors  

Microsoft Academic Search

Gas sensors based on metal oxide semiconductors like tin dioxide are widely used for the detection of toxic and combustible\\u000a gases like carbon monoxide, methane and LPG. One of the problems of such sensors is their lack of sensitivity, which to some\\u000a extent, can be circumvented by using different catalysts. However, highly reactive volatile organic compounds (VOC) coming\\u000a from different

A. Banerjee; A. K. Haldar; J. Mondal; A. Sen; H. S. Maiti

2002-01-01

267

Thermal balance analysis of a micro-thermoelectric gas sensor using catalytic combustion of hydrogen.  

PubMed

A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Q(catalyst) required for 1 mV of ?V(gas) was calculated to be 46.1 ?W. Using these parameters, we find from simulations for the device performance that the expected Q(catalyst) for 200 and 1,000 ppm H? was 3.69 ?W and 11.7 ?W, respectively. PMID:24451468

Nagai, Daisuke; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

2014-01-01

268

Experimental investigation of film cooling effectiveness on gas turbine blades  

E-print Network

high temperature and high pressure blades as an active cooling scheme. In this study, the film cooling effectiveness in different regions of gas turbine blades was investigated with various film hole/slot configurations and mainstream flow conditions...

Gao, Zhihong

2009-05-15

269

Investigation of the oxygen gas sensing performance of Ga 2O 3 thin films with different dopants  

Microsoft Academic Search

The oxygen gas sensing performance of Ga2O3 semiconducting thin films doped with Ce, Sb, W and Zn have been investigated. These thin films have been prepared by the sol–gel process and were deposited on sapphire transducers with inter-digital electrodes and a platinum heater integrated. The sensors were exposed to various concentrations of oxygen gas in an ambient of nitrogen and

Yongxiang Li; Adrian Trinchi; Wojtek Wlodarski; Kosmas Galatsis; Kourosh Kalantar-zadeh

2003-01-01

270

Thin-film optical sensors with silicon-compatible materials.  

PubMed

Antireflection filters based on multilayer stacks of dielectric and polysilicon films on monocrystalline silicon combined with charge collection in different (poly)Si layers can be used to realize sensors with a programmable spectral response controlled by weighted summing of the photocurrents detected in the polysilicon and the substrate. Thus, employing both interference and selective absorption of light yields increased photoelectric efficiency and improved flexibility of spectral control and enables on-chip integration of the detector(s) with the signal conditioning and processing circuits. The potential of thin-film color sensors has been evaluated for this purpose. However, for practical implementation of such structures the problems associated with the realization of reliable photodetectors in polysilicon must also be considered. Phosphorus passivation of the grain-boundary states has been employed to yield polysilicon photodiodes with improved electrical characteristics and reliable light and color detection. We present the design methods of thin-film color sensors employing silicon-compatible materials only. The measurement results of a fabricated structure fully demonstrate that such sensors can be realized with good spectral selectivity. PMID:18259323

Poenar, D P; Wolffenbuttel, R F

1997-07-20

271

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

272

High performance of gas identification by wavelet transform-based fast feature extraction from temperature modulated semiconductor gas sensors  

Microsoft Academic Search

Temperature modulation of semiconductor gas sensors is a powerful strategy to improve selectivity and stability of gas sensors in applications of identifying different gases. This paper presents a new strategy to extract features from the response of a thermally modulated semiconductor sensor for gas identification. This strategy contains two main steps. First, make the sensor work under temperature modulation and

Hui Ding; Haifeng Ge; Junhua Liu

2005-01-01

273

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

274

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

275

Designing an amperometric thick-film microbial BOD sensor.  

PubMed

Thick film oxygen electrodes manufactured by screen print method have been used as a transducer for a biochemical oxygen demand (BOD) sensor. The kinetics of the immobilized yeast, Arxula adeninivorans (Arxula) has been studied. The apparent KM of immobilized Arxula (> 100 microM) is higher than free cells of Arxula (70 microM). The increase in KM caused by the effect of immobilization extends the linear range of the sensor. End-point measurement and quasi-kinetic measurement have been studied comparatively as measurement procedures with a good correlation. The Vmax for end-point measurement is 790.7 microM/s and that for quasi-kinetic measurement is 537.3 microM/s. The limit of detection is calculated 1.24 mg/l BOD. Using the quasi-kinetic measurement, instead of end-point measurements, the measuring time can be reduced from 5-30 min to 100 s. The sensor layer thickness or increase in the layer of covering gel can increase the KM that is accompanied with the extension of the linear range of the sensor. Nevertheless, increase in the layer of covering gel will not increase the saturation signal. Domestic wastewater was checked by the thick film BOD sensor and the results are satisfactory. PMID:11219747

Chan, C; Lehmann, M; Chan, K; Chan, P; Chan, C; Gruendig, B; Kunze, G; Renneberg, R

2000-10-01

276

Detecting insect infestation with poly3-hexylthiophenethin thin film sensor  

NASA Astrophysics Data System (ADS)

The financial losses and destruction of crops due to insect infestation in the United States are estimated by the USDA to exceed 20 billion dollars annually. Much of these losses could be avoided by having a sensor that could effectively identify the early stages of insect infestation. However, traditional detection methods are time consuming, require trained personnel, and are not sufficient for early detection. Several previous research studies showed that emitting organic volatile compounds is a defensive mechanism activated by some plant species after being attacked by herbivores and parasites. Corn, cotton, pine, Brussels sprouts when attacked by Beet army worm, spider mites, bark beetles and caterpillars respectively, emits different blends of plant volatiles including ?-terpinene, ?-pinene, p-cymene, farnesene, limonene and cis-hexenyl acetate, with a concentration of about 50 ppm. Therefore, monitoring for these volatile compounds may enable on-site early detection of insect infestations. In this study, a chemical resistor sensor to detect plant volatiles was designed and fabricated. The sensor platform consists of micro electronically fabricated interdigitated electrodes. On to this platform, a poly3-hexylthiophene (P3HT) thin film was deposited, using a spin coater at 8000 rpm for 30 seconds. The sensor was tested and found to be sensitive to a variety of plant volatiles, including ?-terpinene, ?-pinene, p-cymene, farnesene, limonene and cis-hexenyl acetate at room temperature. These vapors interacted with the P3HT film causing an increase in the resistance of the sensor by more than one order of magnitude

Weerakoon, Kanchana; Li, Suiquing; Shu, Hungjen J.; Chin, Bryan A.

2009-05-01

277

Thin-film thermomechanical sensors embedded in metallic structures  

NASA Astrophysics Data System (ADS)

The ability to monitor in real time the thermo-mechanical responses of tools, equipment, and structural components has been very appealing to the aerospace, automotive, drilling, and manufacturing industries. So far, the challenge has been to instrument the tools, equipment, or structural components with a number of sensors in an economical way and also protect the sensors from the environment which the tools, etc. are exposed to. In this work, a sequence of manufacturing processes that can be used to build thin-film temperature and strain sensors on internal surfaces of metallic structures is proposed and demonstrated. The use of thin-film techniques allows the parallel fabrication of sensor arrays, whereas a layered manufacturing scheme permits the creation of sensors on the internal surfaces of metallic parts and their subsequent embedding. Thin-film sensors are deposited on an aluminum oxide film, which is grown on a stainless steel substrate. The oxide is deposited by reactive sputtering. The sensors are sputter-deposited from alloy targets, shaped via micromachining and partially covered with a passivation layer of aluminum oxide. The thin-film structure is then covered by two protective electroplated layers of copper and nickel for protection during the deposition of the embedding layers. Embedding is accomplished by using a high-power infrared laser to melt an invar powder bed on top of the protective layers. Among the issues that emerged during the definition of the fabrication sequence were: the long-term stability of reactive deposition, the presence of pinholes in the dielectric layers, the optimal combination of materials and thickness of the protective layers, the bonding at the various interfaces, and the heat input and residual stresses resulting from the high-temperature embedding process. Finally, a finite element model was constructed in order to simulate the high-temperature embedding process. The heat transfer analysis performed on the model provides the temperature profiles of all nodes and can be used as a tool for the optimization of the protective layer thickness. Its results can also be used for a stress analysis of the multilayered structure.

Golnas, Anastasios M.

2000-10-01

278

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

279

Optical and Nonlinear Optical Response of Light Sensor Thin Films  

PubMed Central

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 ultrashort pulsed laser excitation all films show extremely intense and ultrafast nonlinear optical (NLO) response. The recorded holography from all these thin films in a degenerate-four-wave-mixing configuration shows extremely large third-order response. For VO2 thin films, an optically induced semiconductor-to-metal phase transition (PT) immediately occurred upon laser excitation. it accompanied. It turns out that the fast excited state dynamics was responsible to the induced PT. For c-Si/SiO2 film, its NLO response comes from the contribution of charge carriers created by laser excitation in conduction band of the c-Si nanoparticles. It was verified by introducing Eu3+ which is often used as a probe sensing the environment variations. It turns out that the entire excited state dynamical process associated with the creation, movement and trapping of the charge carriers has a characteristic 500 ps duration.

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

2005-01-01

280

Study on the MEMS-type gas sensor for detecting a nitrogen oxide gas  

Microsoft Academic Search

In this study, MEMS-based micro gas sensors were prepared by adopting MEMS technology and using sol–gel process. These sensors can be used for application of the air quality system monitoring the automobile indoor atmosphere. An array of MEMS-based gas sensors was designed to achieve low power consumption and high efficiency; this was done by adjusting the heater pattern and line

Jin-Ho Yoon; Jung-Sik Kim

2011-01-01

281

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

282

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

283

Ballistocardiogaphic studies with acceleration and electromechanical film sensors.  

PubMed

The purpose of this research is to demonstrate and compare the utilization of electromechanical film (EMFi) and two acceleration sensors, ADXL202 and MXA2500U, for ballistocardiographic (BCG) and pulse transit time (PTT) studies. We have constructed a mobile physiological measurement station including amplifiers and a data collection system to record the previously mentioned signals and an electrocardiogram signal. Various versions of the measuring systems used in BCG studies in the past are also presented and evaluated. We have showed the ability of the EMFi sensor to define the elastic properties of the cardiovascular system and to ensure the functionality of the proposed instrumentation in different physiological loading conditions, before and after exercise and sauna bath. The EMFi sensor provided a BCG signal of good quality in the study of the human heart and function of the cardiovascular system with different measurement configurations. EMFi BCG measurements provided accurate and repeatable results for the different components of the heart cycle. In multiple-channel EMFi measurements, the carotid and limb pulse signals acquired were detailed and distinctive, allowing accurate PTT measurements. Changes in blood pressure were clearly observed and easily determined with EMFi sensor strips in pulse wave velocity (PWV) measurements. In conclusion, the configuration of the constructed device provided reliable measurements of the electrocardiogram, BCG, heart sound, and carotid and ankle pulse wave signals. Attached EMFi sensor strips on the neck and limbs yield completely new applications of the EMFi sensors aside from the conventional seat and supine recordings. Higher sensitivity, ease of utilization, and minimum discomfort of the EMFi sensor compared with acceleration sensors strengthen the status of the EMFi sensor for accurate and reliable BCG and PWV measurements, providing novel evaluation of the elastic properties of the cardiovascular system. PMID:19713144

Alametsä, J; Värri, A; Viik, J; Hyttinen, J; Palomäki, A

2009-11-01

284

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)

2012-01-01

285

Chemical modification of nanocrystalline tin dioxide for selective gas sensors  

NASA Astrophysics Data System (ADS)

Chemical methods for enhancement of the selectivity of semiconductor metal oxide gas sensors are considered taking SnO2 as an example. Theoretical concepts concerning correlations between the metal oxide chemical composition, crystal structure, surface morphology and the oxide surface reactivity are discussed. Application of such concepts to the design of novel, highly selective sensor materials based on nanocrystalline SnO2 is discussed in detail. Experimental data on the determination of the chemical composition, structure, activity in gas-solid chemical interaction and the sensor properties of such materials are analyzed. The applicability of modern concepts of the chemical activity of the surface in gas-solid reactions to the design of novel metal oxide sensor materials with enhanced selectivity is substantiated. The bibliography includes 133 references.

Krivetskiy, V. V.; Rumyantseva, M. N.; Gaskov, A. M.

2013-10-01

286

Corroles-porphyrins: a teamwork for gas sensor arrays.  

PubMed

Porphyrins provide an excellent material for chemical sensors, and they have been used for sensing species both in air and solution. In the gas phase, the broad selectivity of porphyrins is largely dependant on molecular features, such as the metal ion complexed at the core of the aromatic ring and the peripheral substituents. Although these features have been largely exploited to design gas sensor arrays, so far, little attention has been devoted to modify the sensing properties of these macrocycles by variation of the molecular aromatic ring. In this paper, the gas sensing properties of a porphyrin analog, the corrole, are studied in comparison with those of the parent porphyrin. Results show that changes in the aromatic ring have important consequences on the sensitivity and selectivity of the sensors and that porphyrins and corroles can positively cooperate to enhance the performance of sensor arrays. PMID:25856324

Capuano, Rosamaria; Pomarico, Giuseppe; Paolesse, Roberto; Di Natale, Corrado

2015-01-01

287

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

288

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

289

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

290

The simulation for optimal design of metal film on surface plasmon resonance sensor  

NASA Astrophysics Data System (ADS)

Based on the principle of surface plasmon resonance (SPR) sensor, the influence of mental film was illuminated. According to the MATLAB simulation, the performance of SPR sensor using Au and Ag film was compared. The optimal thickness was 52nm and 38nm, respectively. In view of the features of Au and Ag film, Ag+Au hybrid metal film was proposed. On the basis of simulated result, it could be concluded that the performance of SPR sensor with 50nm composite film (Ag film 20nm ) was excellent.

Chen, HuiBin

2014-11-01

291

Gas Sensor for Volatile Anesthetic Agents Based on Raman Scattering  

NASA Astrophysics Data System (ADS)

Continuous monitoring of respiratory and anesthetic gases during a surgery is of vital importance for the patient safety. Commonly the gas composition is determined by gas chromatography or a combination of IR-spectroscopy and electrochemical sensors. This study presents a concept for an optical sensor based on spontaneous Raman scattering which offers several advantages compared to established systems. All essential components can be detected simultaneously, no sample preparation is necessary and it provides fast response times. To reach the performance of a commonly used gas monitor signal gain has to be increased e.g. by using a multi pass setup.

Schlüter, Sebastian; Popovska-Leipertz, Nadejda; Seeger, Thomas; Leipertz, Alfred

292

The Enhanced Formaldehyde-Sensing Properties of P3HT-ZnO Hybrid Thin Film OTFT Sensor and Further Insight into Its Stability  

PubMed Central

A thin-film transistor (TFT) having an organic–inorganic hybrid thin film combines the advantage of TFT sensors and the enhanced sensing performance of hybrid materials. In this work, poly(3-hexylthiophene) (P3HT)-zinc oxide (ZnO) nanoparticles' hybrid thin film was fabricated by a spraying process as the active layer of TFT for the employment of a room temperature operated formaldehyde (HCHO) gas sensor. The effects of ZnO nanoparticles on morphological and compositional features, electronic and HCHO-sensing properties of P3HT-ZnO thin film were systematically investigated. The results showed that P3HT-ZnO hybrid thin film sensor exhibited considerable improvement of sensing response (more than two times) and reversibility compared to the pristine P3HT film sensor. An accumulation p-n heterojunction mechanism model was developed to understand the mechanism of enhanced sensing properties by incorporation of ZnO nanoparticles. X-ray photoelectron spectroscope (XPS) and atomic force microscopy (AFM) characterizations were used to investigate the stability of the sensor in-depth, which reveals the performance deterioration was due to the changes of element composition and the chemical state of hybrid thin film surface induced by light and oxygen. Our study demonstrated that P3HT-ZnO hybrid thin film TFT sensor is beneficial in the advancement of novel room temperature HCHO sensing technology. PMID:25608214

Tai, Huiling; Li, Xian; Jiang, Yadong; Xie, Guangzhong; Du, Xiaosong

2015-01-01

293

The Enhanced Formaldehyde-Sensing Properties of P3HT-ZnO Hybrid Thin Film OTFT Sensor and Further Insight into Its Stability.  

PubMed

A thin-film transistor (TFT) having an organic-inorganic hybrid thin film combines the advantage of TFT sensors and the enhanced sensing performance of hybrid materials. In this work, poly(3-hexylthiophene) (P3HT)-zinc oxide (ZnO) nanoparticles' hybrid thin film was fabricated by a spraying process as the active layer of TFT for the employment of a room temperature operated formaldehyde (HCHO) gas sensor. The effects of ZnO nanoparticles on morphological and compositional features, electronic and HCHO-sensing properties of P3HT-ZnO thin film were systematically investigated. The results showed that P3HT-ZnO hybrid thin film sensor exhibited considerable improvement of sensing response (more than two times) and reversibility compared to the pristine P3HT film sensor. An accumulation p-n heterojunction mechanism model was developed to understand the mechanism of enhanced sensing properties by incorporation of ZnO nanoparticles. X-ray photoelectron spectroscope (XPS) and atomic force microscopy (AFM) characterizations were used to investigate the stability of the sensor in-depth, which reveals the performance deterioration was due to the changes of element composition and the chemical state of hybrid thin film surface induced by light and oxygen. Our study demonstrated that P3HT-ZnO hybrid thin film TFT sensor is beneficial in the advancement of novel room temperature HCHO sensing technology. PMID:25608214

Tai, Huiling; Li, Xian; Jiang, Yadong; Xie, Guangzhong; Du, Xiaosong

2015-01-01

294

Improvement of sputtered Galfenol thin films for sensor applications  

NASA Astrophysics Data System (ADS)

Galfenol Fe83Ga17 films are sputtered on Si wafers without, and with Ti or Ti/Cu metallic seed layers in order to obtain a magnetoelastic layer which is sensitive to bending deformations of the compound structure. The layer thicknesses range from 100 nm to 5 µm. Layer morphology, texture, and the Villari effect are examined. The texture of the Galfenol films is strongly influenced by the seed layer. No low-index texture components are found for films directly deposited on Si and SiO2. On Ti, a (111) texture is formed on layers with more than 1000 nm thickness. A favorable (110) fiber texture is formed on Ti/Cu. Deforming the bimorphs (Si + layer system) by 0.012%, the Villari effect is detected due to the change in relative permeability. The maximum change occurs for Galfenol films with a thickness of 1 µm on a Ti/Cu buffer layer. The films open a route to the incorporation of magnetoelastic films into integrated magnetoelastic sensor devices.

Adolphi, B.; McCord, J.; Bertram, M.; Oertel, C.-G.; Merkel, U.; Marschner, U.; Schäfer, R.; Wenzel, C.; Fischer, W.-J.

2010-05-01

295

High-Temperature Gas Sensor Array (Electronic Nose) Demonstrated  

NASA Technical Reports Server (NTRS)

The ability to measure emissions from aeronautic engines and in commercial applications such as automotive emission control and chemical process monitoring is a necessary first step if one is going to actively control those emissions. One single sensor will not give all the information necessary to determine the chemical composition of a high-temperature, harsh environment. Rather, an array of gas sensor arrays--in effect, a high-temperature electronic "nose"--is necessary to characterize the chemical constituents of a diverse, high-temperature environment, such as an emissions stream. The signals produced by this nose could be analyzed to determine the constituents of the emission stream. Although commercial electronic noses for near-room temperature applications exist, they often depend significantly on lower temperature materials or only one sensor type. A separate development effort necessary for a high-temperature electronic nose is being undertaken by the NASA Glenn Research Center, Case Western Reserve University, Ohio State University, and Makel Engineering, Inc. The sensors are specially designed for hightemperature environments. A first-generation high-temperature electronic nose has been demonstrated on a modified automotive engine. This nose sensor array was composed of sensors designed for hightemperature environments fabricated using microelectromechanical-systems- (MEMS-) based technology. The array included a tin-oxide-based sensor doped for nitrogen oxide (NOx) sensitivity, a SiC-based hydrocarbon (CxHy) sensor, and an oxygen sensor (O2). These sensors operate on different principles--resistor, diode, and electrochemical cell, respectively--and each sensor has very different responses to the individual gases in the environment. A picture showing the sensor head for the array is shown in the photograph on the left and the sensors installed in the engine are shown in the photograph on the right. Electronics are interfaced with the sensors for temperature control and signal conditioning, and packaging designed for high temperatures is necessary for the array to survive the engine environment.

Hunter, Gary W.

2002-01-01

296

Thick Film Heater for Sensor Application  

NASA Astrophysics Data System (ADS)

A thick film microheater was elaborated. The microheater is intended for fast heating of small volume samples under measurement in optical based system. Thermal analysis of microheater was carried out using finite element method (FEM) for heat transfer calculation as a function of time and space. A nodal heat transfer function was calculated in classical form including all basics mechanisms of heat exchange - heat conduction, convection and radiation were considered. Work focuses on the influence of some construction parameters (ex. length, thermal conductivity of substrate, substrate thickness) on microheater performance. The results show that application of thin substrate of low thermal conductivity and low thickness for miroheater construction and resistor of optimum dimensions leads to significant power consumption decrease and increase of overall optical measurement system performance.

Milewski, J.; Borecki, M.; Kalenik, J.; Król, K.

2014-04-01

297

Nanocrystalline indium oxide-doped tin oxide thin film as low temperature hydrogen sensor  

Microsoft Academic Search

Hydrogen gas, within the concentration range of 100ppm–4vol.%, is successfully sensed at lower operating temperatures, 25 and 50°C, using the Pt-sputtered sol–gel dip-coated nanocrystalline (6–7nm) 6.5mol% In2O3-doped SnO2 semiconductor thin (100–150nm) film sensor. Typically, for 1000ppm of hydrogen, the maximum sensitivity values of 32 and 1600% are observed at 25 and 50°C, respectively; while for 2vol.% hydrogen, the maximum sensitivity

S. Shukla; S. Seal; L. Ludwig; C Parish

2004-01-01

298

Photoacoustic photonic crystal fiber gas sensor  

E-print Network

Photoacoustic spectroscopy (PAS) is a form of laser spectroscopy that has demonstrated very high sensitivity for gas detection. Typically, PAS involves the absorption of a modulated laser beam by the gas species of interest, ...

Chen, Raymond, M. Eng. Massachusetts Institute of Technology

2007-01-01

299

Thermal Sensor Arrays for The Combinatorial Analysis of Thin Films  

NASA Astrophysics Data System (ADS)

Membrane-based thermal sensor arrays were developed for the high-throughput analysis of the thermophysical properties of thin films. The continuous growth of integrated circuits and microelectromechanical systems, as well as the development of functional materials and the optimization of materials properties, have produced the need for instruments capable of fast materials screening and analysis at reduced length scales. Two instruments were developed based on a similar architecture, one to measure thermal transport properties and the other to perform calorimetry measurements. Both have the capability to accelerate the pace of materials development and understanding using combinatorial measurement methods. The shared architecture of the instruments consists of a silicon-based micromachined array of thermal sensors. Each sensor consists of a SiN X membrane and a W heating element that also serves as a temperature gauge. The array design allows the simultaneous creation of a library of thin film samples by various deposition techniques while systematically varying a parameter of interest across the device. The membrane-based sensors have little thermal mass making them extremely sensitive to changes in thermal energy. The nano-thermal transport array has an array of sensors optimized for sensitivity to heat loss. The heat loss is determined from the temperature response of the sensor to an applied current. An analytical model is used with a linear regression analysis to fit the thermal properties of the samples to the temperature response. The assumptions of the analytical model are validated with a finite element model. Measured thermal properties include specific heat, thermal effusivity, thermal conductivity, and emissivity. The technique is demonstrated by measuring the thermal transport properties of sputter deposited Cu multilayers with a total film thickness from 15 to 470 nm. The experimental results compare well to a theory based on electronic thermal transport. The parallel nano-scanning calorimeter (PnSC) has an array of sensors optimized to sense changes in enthalpy. In this case heat loss sensitivity is minimized with sensor geometry and a reference measurement scheme. The minimal heat loss and small addendum result in sensitivity on the order of 10 nJ/K at heating rates on the order of 104 K/s. The sensitivity is demonstrated by measuring the characteristics of the melting transformation of a 25 nm In film. The combinatorial capabilities of the device are demonstrated by creating and analyzing a library of thin-film (290 nm) Ni-Ti-Zr samples with in-plane composition gradients. The Ni-Ti-Zr films are crystallized in-situ by local heating and the temperature dependence of the martensite transformation on Zr content is detected. Further analysis of the Ni-Ti-Zr samples reveals that the as-deposited amorphous samples crystallize in a multi-stage process that is a function of composition. The features of the calorimetry traces are identified with the help of x-ray diffraction measurements of the crystallized samples. Crystallization at these fast heating rates results in suppression of structural relaxation, increased crystallization temperature (allowing the detection of the glass transition), and an ultra-fine nanocrystalline grain structure with non-equilibrium phases. The characteristics of the martensite-austenite phase transformation are investigated by PnSC to determine the effects of high-temperature (900°C) heat treatments and low-temperature (450°C) thermal cycling. Heat treatments produce precipitates that vary with Zr content and alter the transformation temperature. Thermal cycling results in the accumulation of plastic deformation, which relaxes internal stresses and reduces the transformation temperature. This effect, known as thermal fatigue, is reduced in these samples due to the ultra-fine grain structure, which suppresses dislocation mobility.

McCluskey, Patrick James

2011-12-01

300

Modeling thin-film piezoelectric polymer ultrasonic sensors.  

PubMed

This paper presents a model suitable to design and characterize broadband thin film sensors based on piezoelectric polymers. The aim is to describe adequately the sensor behavior, with a reasonable number of parameters and based on well-known physical equations. The mechanical variables are described by an acoustic transmission line. The electrical behavior is described by the quasi-static approximation, given the large difference between the velocities of propagation of the electrical and mechanical disturbances. The line parameters include the effects of the elastic and electrical properties of the material. The model was validated with measurements of a poly(vinylidene flouride) sensor designed for short-pulse detection. The model variables were calculated from the properties of the polymer at frequencies between 100 Hz and 30 MHz and at temperatures between 283 K and 313?K, a relevant range for applications in biology and medicine. The simulations agree very well with the experimental data, predicting satisfactorily the influence of temperature and the dielectric properties of the polymer on the behavior of the sensor. Conversely, the model allowed the calculation of the material dielectric properties from the measured response of the sensor, with good agreement with the published values. PMID:25430142

González, M G; Sorichetti, P A; Santiago, G D

2014-11-01

301

Modeling thin-film piezoelectric polymer ultrasonic sensors  

NASA Astrophysics Data System (ADS)

This paper presents a model suitable to design and characterize broadband thin film sensors based on piezoelectric polymers. The aim is to describe adequately the sensor behavior, with a reasonable number of parameters and based on well-known physical equations. The mechanical variables are described by an acoustic transmission line. The electrical behavior is described by the quasi-static approximation, given the large difference between the velocities of propagation of the electrical and mechanical disturbances. The line parameters include the effects of the elastic and electrical properties of the material. The model was validated with measurements of a poly(vinylidene flouride) sensor designed for short-pulse detection. The model variables were calculated from the properties of the polymer at frequencies between 100 Hz and 30 MHz and at temperatures between 283 K and 313 K, a relevant range for applications in biology and medicine. The simulations agree very well with the experimental data, predicting satisfactorily the influence of temperature and the dielectric properties of the polymer on the behavior of the sensor. Conversely, the model allowed the calculation of the material dielectric properties from the measured response of the sensor, with good agreement with the published values.

González, M. G.; Sorichetti, P. A.; Santiago, G. D.

2014-11-01

302

Micromachined force sensors using thin film nickel-chromium piezoresistors  

NASA Astrophysics Data System (ADS)

Micromachined force/tactile sensors using nickel-chromium piezoresistors have been investigated experimentally and through finite-element analysis. The force sensors were designed with a suspended aluminum oxide (Al2O3) membrane and optimally placed piezoresistors to measure the strain in the membrane when deflected with an applied force. Different devices, each with varying size and shape of both the membrane and the piezoresistors, were designed, fabricated and characterized. The piezoresistors were placed into a half-Wheatstone bridge configuration with two active and two passive nickel-chromium resistors to provide temperature drift compensation. The force sensors were characterized using a load cell and a nanopositioner to measure the sensor response with applied load. Piezoresistive gauge factors in the range of 1-5.2 have been calculated for the thin film nichrome (NiCr 80/20 wt%) from the measured results. The force sensors were calculated to have a noise equivalent force of 65-245 nN.

Nadvi, Gaviraj S.; Butler, Donald P.; Çelik-Butler, Zeynep; Erkin Gönenli, ?smail

2012-06-01

303

Preparation of nanostructured PbS thin films as sensing element for NO2 gas  

NASA Astrophysics Data System (ADS)

In this work, we demonstrate that semiconducting films of AIVBVI compounds, in particular, of nanostructured lead sulfide (PbS) which prepared by chemical bath deposition (CBD), can be used as a sensing element for nitrogen dioxide (NO2) gas. The CBD method is versatile, simple in implementation and gives homogeneous semiconductor structures. We have prepared PbS nanocrystalline thin film at different reaction baths and temperatures. In the course of deposition, variable amounts of additives, such as organic substances among them, were introduced into the baths. The energy dispersive analysis (EDX) confirms the chemical composition of PbS films. A current-voltage (I-V) characterization of Pd/nc-PbS/a-SiC:H pSi(100)/Al Schottky diode structures were studied in the presence of NO2 gas. The gas sensing behavior showed that the synthesized PbS nanocrystalline thin films were influenced by NO2 gas at room temperature. The results can be used for developing an experimental sensing element based on chemically deposited nanostructured PbS films which can be applicable in gas sensors.

Kaci, S.; Keffous, A.; Hakoum, S.; Trari, M.; Mansri, O.; Menari, H.

2014-06-01

304

Chemiresistive gas sensing characteristics of cobalt oxide thin films  

NASA Astrophysics Data System (ADS)

We report synthesis of 100 nm thick cobalt oxide films - prepared by electron-beam evaporation of Co onto quartz (Q- films) and c-plane sapphire substrate (S- films) followed by oxygen annealing. Films have been characterized for their structure and morphology by using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The prepared films have been investigated for their chemiresistive gas sensing characteristics for a host of test gases (CH4, CO, NO2, Cl2, NH3 and H2S) as a function of operating temperature (between 50 and 350°C) and gas concentration (3-30 ppm). We demonstrate that both Q and S-films are highly selective to H2S at an operating temperature of 250°C. However it has been observed that films prepared on sapphire show much less base resistance drift as compared to the films on quartz substrate.

Balouria, Vishal; Kumar, Arvind; Samanta, S.; Bhattacharya, S.; Singh, A.; Debnath, A. K.; Mahajan, Aman; Bedi, R. K.; Aswal, D. K.; Gupta, S. K.

2012-06-01

305

Thermal Balance Analysis of a Micro-Thermoelectric Gas Sensor Using Catalytic Combustion of Hydrogen  

PubMed Central

A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Qcatalyst required for 1 mV of ?Vgas was calculated to be 46.1 ?W. Using these parameters, we find from simulations for the device performance that the expected Qcatalyst for 200 and 1,000 ppm H2 was 3.69 ?W and 11.7 ?W, respectively. PMID:24451468

Nagai, Daisuke; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

2014-01-01

306

A non-invasive ultrasonic gas sensor for binary gas mixtures  

Microsoft Academic Search

A non-invasive gas sensor has been fabricated for quantitative measurement of a specific gas in a binary mixture such as H2, He, etc. mixed in air, based on time of flight (TOF) measurements of the ultrasonic signal. A test gas with different concentration was mixed in air and its concentration was determined using the observed TOF data and a theoretically

J. C. Vyas; V. R. Katti; S. K. Gupta; J. V. Yakhmi

2006-01-01

307

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

308

AZO thin film-based UV sensors: effects of RF power on the films  

NASA Astrophysics Data System (ADS)

Al-doped zinc oxide (AZO) thin films of thickness 150 nm were deposited on polyethylene terephthalate (PET) substrates by radio frequency (RF) magnetron sputtering method under various RF powers in the range of 25-100 W. Structural, morphological, optical and electrical properties of the films were investigated by X-ray diffractometer, atomic force microscope, UV-Vis spectrometer and Hall effect measurement system. All the obtained films had a highly preferred orientation along [002] direction of the c-axis perpendicular to the flexible PET substrate and had a high-quality surface. The energy band gap (E g) values of the films varied in the range of 3.30-3.43 eV. The minimum resistivity of 1.84 × 10-4 ? cm was obtained at a 50 W RF power. The small changes in the RF power had a critical important role on the structural, optical and electrical properties of the sputtered AZO thin films on flexible PET substrate. In addition, UV sensing of the fabricated AZO thin film-based sensors was explored by using current-voltage (I-V) characteristics. The sensors were sensitive in the UV region of the electromagnetic spectrum.

Akin, Nihan; Ceren Baskose, U.; Kinaci, Baris; Cakmak, Mehmet; Ozcelik, Suleyman

2015-02-01

309

TiO{sub 2}/PANI And MWNT/PANI Composites Thin Films For Hydrogen Gas Sensing  

SciTech Connect

The MWNT and TiO{sub 2} doped Polyaniline (PANI) composites were synthesized by In-situ chemical oxidative polymerization method at low temperature. The MWNT/PANI and TiO{sub 2}/PANI composite thin films were prepared using spin coating method onto finger type interdigited electrodes to develop the chemiresistor type gas sensor for hydrogen gas sensing application. It was observed that the MWNT and TiO{sub 2} doped PANI composite thin films show a higher response in comparision to neat PANI. The structural and morphological properties of these composite films were characterized by X-Ray differaction (XRD) pattern and sccaning electrone microscopy (SEM) respectively.

Srivastava, Subodh; Kumar, Sumit; Agrawal, Shweta; Saxena, Arpita; Choudhary, B. L.; Mathur, Shubhra; Singh, M.; Vijay, Y. K. [Department of Physics, University of Rajasthan, Jaipur-302004 (India)

2010-12-01

310

Thermomechanical analysis of micro-drop coated gas sensors  

Microsoft Academic Search

The paper discusses the mechanical and thermal behaviour of drop-coated micromachined gas sensors. A laboratory optimised micromachined hotplate has been developed and coated with SnO2 sensing pastes by means of microdropping technology. Different drop dimensions and geometries have been investigated with regard to their influence on the power consumption, the time response and the mechanical behaviour of the whole sensor.

J. Puigcorbé; A. Vilà; J. Cerdà; A. Cirera; I. Gràcia; C. Cané; J. R. Morante

2002-01-01

311

Air pollution monitoring using semiconductor toxic gas sensors  

Microsoft Academic Search

The SnO2 toxic gas sensors, which are usually used in alarm systems, were integrated in air pollution monitoring systems for ammonia, hydrogen sulphide, carbon monoxide and freon (R113 and R22). The sensitivity curves were extended for small concentrations using a parameter extraction method based on a simple semiconductor theory and on a n-dimensional minimisation algorithm. The sensors are working in

F. Caldararu; M. Caldararu; A. Jelev; A. Iacob

1994-01-01

312

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. PMID:23443378

Kim, Eungyeong; Lee, Seok; Kim, Jae Hun; Kim, Chulki; Byun, Young Tae; Kim, Hyung Seok; Lee, Taikjin

2012-01-01

313

Enhanced hydrogen gas response of Pd nanoparticles-decorated single walled carbon nanotube film/SiO2/Si heterostructure  

NASA Astrophysics Data System (ADS)

A new type carbon nanotube-based gas sensor: palladium nanoparticles decorated single walled carbon nanotube film/SiO2/Si (Pd-SWCNT film/SiO2/Si) heterostructures were fabricated by a simple and practical filtration method. When used for hydrogen (H2) sensing, the Pd-SWCNT film/SiO2/p-Si heterostructure shows very high H2 response, which is tens of times higher than that of Pd-SWCNT film resistance-type H2 sensor in this paper and is superior to those of carbon nanotube-based resistance-type H2 sensors reported previously. The mechanism of the enhanced H2 response can be explained by thermionic emission theory and interfacial effect.

Du, Yonggang; Xue, Qingzhong; Zhang, Zhongyang; Xia, Fujun; Liu, Zilong; Xing, Wei

2015-02-01

314

Illicit material detector based on gas sensors and neural networks  

NASA Astrophysics Data System (ADS)

In accordance with its missions, le Centre de Recherches et d'Etudes de la Logistique de la Police Nationale francaise (CREL) has been conducting research for the past few years targeted at detecting drugs and explosives. We have focused our approach of the underlying physical and chemical detection principles on solid state gas sensors, in the hope of developing a hand-held drugs and explosives detector. The CREL and Laboratory and Scientific Services Directorate are research partners for this project. Using generic hydrocarbon, industrially available, metal oxide sensors as illicit material detectors, requires usage precautions. Indeed, neither the product's concentrations, nor even the products themselves, belong to the intended usage specifications. Therefore, the CREL is currently investigating two major research topics: controlling the sensor's environment: with environmental control we improve the detection of small product concentration; determining detection thresholds: both drugs and explosives disseminate low gas concentration. We are attempting to quantify the minimal concentration which triggers detection. In the long run, we foresee a computer-based tool likely to detect a target gas in a noisy atmosphere. A neural network is the suitable tool for interpreting the response of heterogeneous sensor matrix. This information processing structure, alongside with proper sensor environment control, will lessen the repercussions of common MOS sensor sensitivity characteristic dispersion.

Grimaldi, Vincent; Politano, Jean-Luc

1997-02-01

315

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

316

Optical corrosion sensor based on fiber Bragg grating electroplated with Fe-C film  

NASA Astrophysics Data System (ADS)

An optical fiber corrosion sensor (OFCS) based on iron-carbon (Fe-C) film was researched. OFCS was formed by electroplating a Fe-C film on fiber Bragg grating (FBG) metalized with silver film by magnetron sputtering. There was a more than 430-pm change of FBG wavelength when Fe-C film was seriously corroded. Compared to electrochemical method, the optical fiber sensor shows dominance in long-lasting monitoring of corrosion. The electric signal was broken off after the 20-h corrosion of Fe-C film, while the optical fiber sensor's monitoring lasted more than 40 days.

Zheng, Xing; Hu, Wenbin; Zhang, Ning; Gao, Min

2014-07-01

317

Films of lutetium bisphthalocyanine nanowires as electrochemical sensors.  

PubMed

Lutetium bisphthalocyanine (LuPc(2)) nanowires have been successfully obtained by electrophoretic deposition (EPD). The influence of the deposition conditions and annealing in the structure of the films has been studied by AFM, SEM, X-ray diffraction (XRD), UV-vis absorption, and near-infrared (NIR). The electrochemical properties of the EDP films immersed in different electrolytic solutions (KCl, MgCl(2), KClO(4), HCl, and NaOH) indicate that anions diffuse inside the film to maintain the electroneutrality and the kinetics follows the Randles-Sevcik equation. The stability of the response increases strongly upon annealing due to the improvement of the adhesion of the sensitive material to the substrate. The EPD films have been successfully used to detect caffeic acid (an antioxidant of interest in the food industry). The anodic peak associated with the oxidation of caffeic acid appears at 0.54 V and is linearly dependent on the caffeic acid concentration in the 6 × 10(-5) M to 5 × 10(-4) M range with a detection limit of 3.12 × 10(-5) M. The electrochemical behavior of the annealed LuPc(2) EPD films is similar to that observed using Langmuir-Blodgett (LB) nanostructured films. However, the different molecular organization of the molecules inside the film causes differences in the shape and position of the peaks. Although LuPc(2) sensors prepared with both EPD and LB techniques provide stable and reproducible responses, the use of EPD is preferred for real sensing applications because of its lower cost, shorter preparation time, and longer lifetime. PMID:21082798

Martín, Mónica Gay; Rodríguez-Méndez, Maria Luz; de Saja, Jose Antonio

2010-12-21

318

Niobium doped lead zirconate titanate films for infrared sensor application  

NASA Astrophysics Data System (ADS)

Nb-doped lead zirconate titanate with formula Pb1-x/2 Nbx(Zr0.2Ti0.8)1-xO 3 (x=0, 0.01, 0.02, 0.03, 0.04, and abbreviated as PNZT) films with two thicknesses: one of approximately 200 nm and the other of 1 mum, were grown on platinized silicon (Pt/TiOx/SiO2/Si) substrates using the method of chemical solution deposition. These chemical precursors were prepared in-house, and through careful control of the processing procedures high quality films were grown. All the films exhibit highly preferred (111) orientation without any presence of the impurity phase. We systematically investigated the Nb doping effect on the electrical properties of PZT films. Results indicate that Nb belongs to a class of soft dopants for lead zirconate titanate films, and as a result it increases the ferroelectric polarization, pyroelectric coefficient, dielectric constant and tan delta loss. In the capacitors with the configuration of Pt/PNZT/Pt, the leakage current at low electric fields is dominated by the interface-controlled Schottky emission, whereas bulk-controlled Frenkel-Poole emission dominates at high electric fields. Nb-doping up to 2 atomic % can remarkably suppress the Frenkel-Poole emission process. The suppression of mobile oxygen vacancies by Nb donor dopants lowered the leakage current and increases the domain wall mobility. Study also shows that 1% Nb doped PZT films exhibit the highest pyroelectric coefficient, figure of merit and voltage response among all the samples. Therefore these films with such superior properties are potential candidates for applications, especially for fabrication of uncooled pyroelectric IR sensors with better performance.

Han, Hui

319

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

320

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

321

A poly(vinylidene fluoride)-coated ZnO film bulk acoustic resonator for nerve gas detection  

NASA Astrophysics Data System (ADS)

We apply the film bulk acoustic resonator for the detection of nerve gas. The resonator is consisted of a ZnO piezoelectric stack and a W/SiO2 Bragg reflector. Poly(vinylidene fluoride) (PVDF) is used as the sensing coating to adsorb the analyte under test. The testing results show that our proposed sensor can yield a sensitive, reversible and reproducible response to nerve gas. The relationship between the frequency shifts and the concentrations of the nerve gas exhibits a perfect linear correlation in the range of 10-50 ppm. The gas sensitivity of the proposed sensor is 718 kHz ppm-1, which is several orders of magnitude higher than that of a quartz crystal microbalance with the same sensitive coating. This study proves that it is feasible to use the PVDF-coated thin film bulk acoustic resonator for the detection of the traced nerve gas.

Chen, Da; Wang, Jingjing; Li, Dehua; Liu, Yijian; Song, Hongwei; Liu, Qixin

2011-08-01

322

Gas Main Sensor and Communications Network System  

Microsoft Academic Search

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

Hagen Schempf

2006-01-01

323

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

324

High temperature LTCC package for gas sensor  

Microsoft Academic Search

Ceramic technologies, especially LTCC (Low Temperature Co-fired Ceramics), offer a reliable platform to build highly stable and reliable sensors and packages, possible for application in harsh environment such as high temperature, high pressure, aggressive media and space. LTCC allows also to fabricate resistors, capacitors, inductors, heaters and many other passive components buried within ceramic substrate. In this paper package for

Damian Nowak; Stanislaw Sawicki; Andrzej Dziedzic

2010-01-01

325

NO x gas sensing characteristics of WO 3 thin films activated by noble metals (Pd, Pt, Au) layers  

Microsoft Academic Search

WO3-based gas sensor devices have been fabricated by reactive rf sputtering on glass substrates. Palladium (Pd), platinum (Pt), gold (Au) noble metals (100–600 Å) were evaporated as activator layers onto WO3 thin films and Al layers (1500 Å) were sputtered on top of them as upper electrodes for sensor output. The described sensing element was found to possess excellent sensitivity

M Penza; C Martucci; G Cassano

1998-01-01

326

Selective CO Gas Detection of Zn 2 SnO 4 Gas Sensor  

Microsoft Academic Search

The ability of semiconductor gas sensors to differentiate between gases is essential but difficult to obtain. In this study, Zn2SnO4 was made to be CO selective and the possible mechanism for the selectivity was studied.

Ji Haeng Yu; Gyeong Man Choi

2002-01-01

327

?-Amylase sensor based on the degradation of oligosaccharide hydrogel films monitored with a quartz crystal sensor.  

PubMed

?-Amylase hydrolyses starch molecules to produce smaller oligosaccharides and sugars. Amylases are of great importance in biotechnology and find application in fermentation, detergents, food and the paper industry. The measurement of ?-amylase activity in serum and urine has been used in the diagnosis of acute pancreatitis. Salivary amylase has also been shown to be a stress indicator. Sensor coatings suitable for the detection of ?-amylase activity have been developed. Oligosaccharides such as glycogen and amylopectin were spin-coated onto gold coated quartz crystals with a base frequency of 10 MHz. The films were subsequently cross-linked with hexamethylene diisocyanate. Film degradation was monitored with a quartz crystal microbalance (QCM) and electrochemical impedance measurements. The films were shown to be stable in phosphate buffered saline (PBS). Addition of ?-amylase to the solution resulted in the rapid degradation of the films. The maximum rate of degradation was found to be strongly dependent on the amylase activity in the range typically found in serum when diagnosing pancreatitis (0.08-8 U/ml). Sensor responses in serum were found to be very similar to those obtained in buffer indicating the absence of non-specific binding. PMID:25266253

Gibbs, Martin John; Biela, Anna; Krause, Steffi

2015-05-15

328

Polymer Film SAW Sensors for Chemical Agent Detection  

Microsoft Academic Search

SAW sensors using three different kinds of polymers to detect chemical agents (DMMP, CH3CN and CH2Cl2) have been fabricated and their gas response characteristics were extensively investigated. Interdigital transducer (IDT) line width of SAW device is designed to have 3, 4, 6, 8, 20 ? for the corresponding central frequency 264, 198, 132, 99 and 39.6 MHz, respectively. The IDT

Byung-Su Joo; Jung-Hoon Lee; Eun-Woo Lee; Kap-Duk Song; Duk-Dong Lee

329

Organic field-effect transistor-based gas sensors.  

PubMed

Organic field-effect transistors (OFETs) are one of the key components of modern organic electronics. While the past several decades have witnessed huge successes in high-performance OFETs, their sophisticated functionalization with regard to the responses towards external stimulations has also aroused increasing attention and become an important field of general concern. This is promoted by the inherent merits of organic semiconductors, including considerable variety in molecular design, low cost, light weight, mechanical flexibility, and solution processability, as well as by the intrinsic advantages of OFETs including multiparameter accessibility and ease of large-scale manufacturing, which provide OFETs with great potential as portable yet reliable sensors offering high sensitivity, selectivity, and expeditious responses. With special emphases on the works achieved since 2009, this tutorial review focuses on OFET-based gas sensors. The working principles of this type of gas sensors are discussed in detail, the state-of-the-art protocols developed for high-performance gas sensing are highlighted, and the advanced gas discrimination systems in terms of sensory arrays of OFETs are also introduced. This tutorial review intends to provide readers with a deep understanding for the future design of high-quality OFET gas sensors for potential uses. PMID:25727357

Zhang, Congcong; Chen, Penglei; Hu, Wenping

2015-04-10

330

Gas permeability in polymer- and surfactant-stabilized bubble films.  

PubMed

The gas permeabilities of thin liquid films stabilized by poly(N-isopropylacrylamide) (PNIPAM) and PNIPAM-SDS (sodium dodecyl sulfate) mixtures are studied using the "diminishing bubble" method. The method consists of forming a microbubble on the surface of the polymer solution and measuring the shrinking rates of the bubble and the bubble film as the gas diffuses from the interior to the exterior of the bubble. PNIPAM-stabilized films exhibit variable thicknesses and homogeneities. Interestingly, despite these variable features, the gas permeability of the film is determined principally by the structure of the adsorbed polymer layer that provides an efficient gas barrier with a value of gas permeability coefficient that is comparable to that of an SDS Newton black film. In the presence of SDS, both the film homogeneity and the gas permeability coefficient increase. These changes are related to interactions of PNIPAM with SDS in the solution and at the interface, where coadsorption of the two species forms mixed layers that are stable but that are more porous to gas transfer. The mixed PNIPAM-SDS layers, studied previously for a single water-air interface by neutron reflectivity, are further characterized here in a vertical free-draining film using X-ray reflectivity. PMID:17004816

Andreatta, Gaëlle; Lee, Lay-Theng; Lee, Fuk Kay; Benattar, Jean-Jacques

2006-10-01

331

Examining graphene field effect sensors for ferroelectric thin film studies.  

PubMed

We examine a prototype graphene field effect sensor for the study of the dielectric constant, pyroelectric coefficient, and ferroelectric polarization of 100-300 nm epitaxial (Ba,Sr)TiO3 thin films. Ferroelectric switching induces hysteresis in the resistivity and carrier density of n-layer graphene (n = 1-5) below 100 K, which competes with an antihysteresis behavior activated by the combined effects of electric field and temperature. We also discuss how the polarization asymmetry and interface charge dynamics affect the electronic properties of graphene. PMID:23924380

Rajapitamahuni, A; Hoffman, J; Ahn, C H; Hong, X

2013-09-11

332

Electronic sensors built on nanostructured cerium oxide films  

Microsoft Academic Search

The influence of the technical parameters of nanostructured CeO\\u000a x\\u000a film production on electronic, structural, optical, and photoelectronic characteristics has been studied for their practical\\u000a application as the active element of various microelectronic sensors—such as high-performance photoresistors, MOS-photodiodes\\u000a for bioluminescence registration, ion-selective field-effect transistor (ISFETs), and MOS-varactors indicating pH changing\\u000a as a result of biochemical processes. X-ray photoelectron spectroscopy analysis

A. N. Shmyreva; A. V. Borisov; N. V. Maksimchuk

2010-01-01

333

Hybrid organic/inorganic ambipolar thin film transistor chemical sensor  

NASA Astrophysics Data System (ADS)

An ambipolar hybrid organic-inorganic thin film transistor, consisting of pentacene and zinc oxide as semiconductors, is reported. The current-voltage characteristics in different operational modes are studied. The transistor is employed as a chemical vapor sensor, operating at room temperature. In p-channel accumulation mode, which is dominated by hole transport, a decrease of current with the introduction of analyte is observed, while in the n-channel triode mode, in which the current is predominantly contributed by electron transport, an increase in current with analyte delivery is observed. A qualitative model based on dipole interaction is proposed to explain the sensing activity.

Dutta, Soumya; Lewis, Shannon D.; Dodabalapur, Ananth

2011-05-01

334

Design of micro-sensor-array detector for toxic gas  

NASA Astrophysics Data System (ADS)

To quickly measure the trace concentration of the single component toxic gas (e.g. sarin), a micro-array toxic gas detector is designed. A 3 x 3 gas sensor array with metalloporphyrins as sensitive materials is introduced. A micro-capsule that can be easy to be loaded and unloaded is designed for the gas reaction. A fiber-array optical path is designed, which is based on the principle that gas sensors will show different colors after reaction with the toxic gas. The tricolor information about the concentration of gas is collected by the color liner CCD. A control handling system with C8051F021 MCU as the core is implemented and embedded into the detector to perform the functions of gas sampling, data collection and analysis calculation. Data acquisition experimental results show that the proposed scheme can effectively collect the color information after gas reaction. Moreover, the system has many important advantages, such as small size, compact structure, high degree of automation, fast detection speed and high performance-cost ratio, etc.

Liao, Hai-yang; Tian, Peng

2010-08-01

335

Electrodes for solid state gas sensor  

DOEpatents

A mixed potential electrochemical sensor for the detection of gases has a ceria-based electrolyte with a surface for exposing to the gases to be detected, and with a reference wire electrode and a sensing wire electrode extending through the surface and fixed within the electrolyte as the electrolyte is compressed and sintered. The electrochemical sensor is formed by placing a wire reference electrode and a wire sensing electrode in a die, where each electrode has a first compressed planar section and a second section depending from the first section with the second section of each electrode extending axially within the die. The die is filled with an oxide-electrolyte powder and the powder is pressed within the die with the wire electrodes. The wire-electrodes and the pressed oxide-electrolyte powder are sintered to form a ceramic electrolyte base with a reference wire electrode and a sensing wire electrode depending therefrom.

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

2007-05-08

336

Electrodes for solid state gas sensor  

DOEpatents

A mixed potential electrochemical sensor for the detection of gases has a ceria-based electrolyte with a surface for exposing to the gases to be detected, and with a reference wire electrode and a sensing wire electrode extending through the surface and fixed within the electrolyte as the electrolyte is compressed and sintered. The electrochemical sensor is formed by placing a wire reference electrode and a wire sensing electrode in a die, where each electrode has a first compressed planar section and a second section depending from the first section with the second section of each electrode extending axially within the die. The die is filled with an oxide-electrolyte powder and the powder is pressed within the die with the wire electrodes. The wire-electrodes and the pressed oxide-electrolyte powder are sintered to form a ceramic electrolyte base with a reference wire electrode and a sensing wire electrode depending therefrom.

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

2003-08-12

337

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

338

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

339

Investigation of thiol derivatized gold nanoparticle sensors for gas analysis  

NASA Astrophysics Data System (ADS)

Analysis of volatile organic compounds (VOCs) in air and exhaled breath by sensor array is a very useful testing technique. It can provide non-invasive, fast, inexpensive testing for many diseases. Breath analysis has been very successful in identifying cancer and other diseases by using a chemiresistor sensor or array with gold nanoparticles to detect biomarkers. Acetone is a biomarker for diabetes and having a portable testing device could help to monitor diabetic and therapeutic progress. An advantage to this testing method is it is conducted at room temperature instead of 200 degrees Celsius. 3. The objective of this research is to determine the effect of thiol derivatized gold nanoparticles based on sensor(s) detection of VOCs. The VOCs to be tested are acetone, ethanol, and a mixture of acetone and ethanol. Each chip is tested under all three VOCs and three concentration levels (0.1, 1, and 5.0 ppm). VOC samples are used to test the sensors' ability to detect and differentiate VOCs. Sensors (also referred to as a chip) are prepared using several types of thiol derivatized gold nanoparticles. The factors are: thiol compound and molar volume loading of the thiol in synthesis. The average resistance results are used to determine the VOC selectivity of the sensors tested. The results show a trend of increasing resistance as VOC concentration is increased relative to dry air; which is used as baseline for VOCs. Several sensors show a high selectivity to one or more VOCs. Overall the 57 micromoles of 4-methoxy-toluenethiol sensor shows the strongest selectivity for VOCs tested. 3. Gerfen, Kurt. 2012. Detection of Acetone in Air Using Silver Ion Exchanged ZSM-5 and Zinc Oxide Sensing Films. Master of Science thesis, University of Louisville.

Stephens, Jared S.

340

Mobile gas sensor and source detector  

Microsoft Academic Search

The goal of the project is to develop a program for the navigation of a miniature mobile robot Khepera II (www.k-team.com) towards a gas source. The project would involve programming of existing hardware using any of the following platforms: C, C++, MATLAB, or LabVIEW. Existing hardware to be utilized include the Khepera II robot and a connected gas-sensing module. The

Chu Heng He; Samir El-Kilani; Milutin Stanacevic

2010-01-01

341

Purely thermal wave based nonchemical photopyroelectric gas sensor: Application to hydrogen  

E-print Network

, leading to considerable research efforts towards the development of hydrogen gas sensors. MostPurely thermal wave based nonchemical photopyroelectric gas sensor: Application to hydrogen of Mechanical Engineering and Center jbr Hydrogen and Electrochemical Studies (CHES), University of Toronto

Mandelis, Andreas

342

Discrimination of gas-phase emissions from building material samples by combining two gas-sensor arrays  

E-print Network

Discrimination of gas-phase emissions from building material samples by combining two gas.ramalho@cstb.fr Keywords: Gas sensor array, Building material, Discrimination, Feature extraction Introduction As part, experiments have been performed to assess the discrimination power of two gas-sensor systems as regards

Paris-Sud XI, Université de

343

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. PMID:24113681

Wang, Qihui; Xie, Lijun; Zhu, Bo; Zheng, Yao; Cao, Shihua

2013-01-01

344

A High-Precision NDIR Gas Sensor for Automotive Applications  

Microsoft Academic Search

A new high-precision spectroscopic gas sensor measuring carbon dioxide (CO2) for harsh environmental conditions of automotive applications is presented. The carbon dioxide concentration is the primary parameter for sensing in cabin air quality, as well as an important safety parameter when R744 (carbon dioxide) is used as the refrigerant in the air conditioning system. The automotive environment challenges the potential

Robert Frodl; Thomas Tille

2006-01-01

345

On Optimization of Sensor Selection for Aircraft Gas  

E-print Network

1 On Optimization of Sensor Selection for Aircraft Gas Turbine Engines Ramgopal Mushini Dan Simon rotor speed 3. Fan exit pressure 4. Booster inlet pressure 5. HPC (high pressure compressor) inlet of natural selection · A highly simplified computational model of biological evolution #12;17 Genetic

Simon, Dan

346

Adsorption semiconductor gas sensors and heterogeneous catalytic reaction mechanisms  

SciTech Connect

The sufficiently general kinetic characterization of semiconductor gas sensors may be obtained by the analysis of the real mechanisms of chemical reactions which take place on the surface. The authors have considered the reaction model of surface redox processes which was proved to be true for heterogeneous catalytic oxidation by oxygen of a large variety of organic and inorganic substances.

Vorotyntsev, V.; Maksimovich, N.; Yeremina, L.; Kaskevich, O.; Nikitina, N. [SONAR Research Center for Biotechnological Systems, Kyiv (Ukraine)

1996-12-31

347

General characteristics of thermally cycled tin oxide gas sensors  

Microsoft Academic Search

The response, measured as conductance, of thermally cycled tin oxide gas sensors was studied to determine the potential inherent in this technique with respect to increased selectivity and sensitivity. It was found that the range of cycle temperature as well as the period of the cycle had a critical effect on the amount of information that could be extracted from

W. M. Sears; K. Colbow; F. Consadori

1989-01-01

348

Metal Oxide Semiconductor Gas Sensors and Neural Networks  

E-print Network

Olfaction Metal Oxide Semiconductor Gas Sensors and Neural Networks M. W. Siegel Carnegie Mellon four classes of chemicals in water solution on our tongues, and smell or olfaction, our ability to motivate autonomous activity. #12;2 First, I describe the characteristics of metal oxide semiconductor (MOS

Siegel, Mel

349

Improved Sensitivity Spontaneous Raman Scattering Multi-Gas Sensor  

SciTech Connect

We report a backward-wave spontaneous-Raman multi-gas sensor employing a hollow-core photonic-bandgap-fiber to contain gasses and increase interaction length. Silica Raman noise and detection speed are reduced using a digital spatial filter and a cladding seal.

Michael P. Buric; Kevin P. Chen; Joel Falk; Steven D. Woodruff1

2009-01-01

350

Multielement uncooled sensors based on organic pyroelectric films integrated with CCD  

Microsoft Academic Search

We present some new experimental results on physical properties and time behavior of polycyclic organic compound (TADPh) and polyvinylidene fluoride (PVDF) pyroelectric films for uncooled IR array sensors. The thin films fabrication technologies were optimized as regard to the best figure of merit and to compatibility with CMOS technology. We developed the fabrication process of uncooled pyroelectric IR sensors with

Vladimir Chernokozhin; Eugeny Pevtsov; Marina Pospelova; Alexander Sigov

1999-01-01

351

Fabrication and characterization of all-thin-film magnetoelectric sensors Peng Zhao,1,a  

E-print Network

Fabrication and characterization of all-thin-film magnetoelectric sensors Peng Zhao,1,a Zhenli Zhao online 19 June 2009 ac magnetic field sensors based on thin-film magnetoelectric ME devices operating. © 2009 American Institute of Physics. DOI: 10.1063/1.3157281 The principle of the magnetoelectric ME

Rubloff, Gary W.

352

A CMOS Analog Front-End interface IC for gas sensors  

Microsoft Academic Search

This paper presents a gas sensor readout IC for amperometric and conductometric electrochemical sensors. The Analog Front-End (AFE) readout circuit enables tracking long term exposure to hazardous gas fumes in diesel and gasoline equipment, which may be correlated to diseases. The AFE reads out the output of eight conductometric sensor arrays and eight amperometric sensor arrays. The IC consists of

Hyuntae Kim; Bertan Bakkaloglu

2010-01-01

353

Increasing the selectivity and sensitivity of gas sensors for the detection of explosives  

NASA Astrophysics Data System (ADS)

Over the past decade, the use of improvised explosive devices (IEDs) has increased, domestically and internationally, highlighting a growing need for a method to quickly and reliably detect explosive devices in both military and civilian environments before the explosive can cause damage. Conventional techniques have been successful in explosive detection, however they typically suffer from enormous costs in capital equipment and maintenance, costs in energy consumption, sampling, operational related expenses, and lack of continuous and real-time monitoring. The goal was thus to produce an inexpensive, portable sensor that continuously monitors the environment, quickly detects the presence of explosive compounds and alerts the user. In 2012, here at URI, a sensor design was proposed for the detection of triacetone triperoxide (TATP). The design entailed a thermodynamic gas sensor that measures the heat of decomposition between trace TATP vapor and a metal oxide catalyst film. The sensor was able to detect TATP vapor at the part per million level (ppm) and showed great promise for eventual commercial use, however, the sensor lacked selectivity. Thus, the specific objective of this work was to take the original sensor design proposed in 2012 and to make several key improvements to advance the sensor towards commercialization. It was demonstrated that a sensor can be engineered to detect TATP and ignore the effects of interferent H2O2 molecules by doping SnO2 films with varying amounts of Pd. Compared with a pure SnO2 catalyst, a SnO2, film doped with 8 wt. % Pd had the highest selectivity between TATP and H2O2. Also, at 12 wt. % Pd, the response to TATP and H2O2 was enhanced, indicating that sensitivity, not only selectivity, can be increased by modifying the composition of the catalyst. An orthogonal detection system was demonstrated. The platform consists of two independent sensing mechanisms, one thermodynamic and one conductometric, which take measurements from the same catalyst simultaneously and provide a redundancy in response for positive explosive identification. TATP, 2,6-DNT and ammonium nitrate were reliably detected. Each analyte displayed a unique conductometric signature and the results indicated a detection limit at the ppb level. A preconcentrator was designed to enhance the sensitivity of the sensor and was successfully demonstrated. The magnitude of the sensor response increased from by 50% and the preconcentrator could be operated semi-continuously, maintaining one of the most attractive features of this sensor platform: the capability to operate in real time. A method to filter out extraneous heat signals from sensor response using a dynamic control was also successfully demonstrated and will likely be a fixture in all sensor experimentation and design moving forward. Finally, two MEMS based sensor platforms were designed and fabricated. It was theoretically demonstrated that the newest iteration of the MEMS sensor consumes considerably less power due to thinner membranes, a smaller active surface area and an overall smaller thermal mass, allowing for the possibility of creating networks of sensor arrays, even in a portable device.

Mallin, Daniel

354

Annealed Ce Doped ZnO Coated Fiber Optic Gas Sensor  

NASA Astrophysics Data System (ADS)

Fiber optic sensor based on cladding modification method for detecting various gas emissions such as ammonia methanol, and ethanol is proposed. The Ce doped ZnO annealed at 500 and 1200 °C are used as a gas sensing material. The spectral characteristics of the gas sensor are studied for different concentrations (0-500 ppm) of gases. The sensor exhibits a linear variation in the output light intensity with the concentration. The gas sensitivity and selectivity of the sensor is discussed briefly.

Renganathan, B.; Sastikumar, D.; Gobi, G.; Yogamalar, N. Rajeswari; Bose, A. Chandra

2011-10-01

355

Thin Film Ceramic Strain Sensor Development for Harsh Environments: Identification of Candidate Thin Film Ceramics to Test for Viability for Static Strain Sensor Development  

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 a thorough literature search for ceramics that have the potential for application as high temperature thin film strain gauges, reviewing potential candidate materials for chemical & physical compatibility with NASA GRC's microfabrication procedures and substrates.

Wrbanek, John D.; Fralick, Gustave C.; Hunter, Gary W.

2006-01-01

356

Thin Film Physical Sensor Instrumentation Research and Development at NASA Glenn Research Center  

NASA Technical Reports Server (NTRS)

A range of thin film sensor technology has been demonstrated enabling measurement of multiple parameters either individually or in sensor arrays including temperature, strain, heat flux, and flow. Multiple techniques exist for refractory thin film fabrication, fabrication and integration on complex surfaces and multilayered thin film insulation. Leveraging expertise in thin films and high temperature materials, investigations for the applications of thin film ceramic sensors has begun. The current challenges of instrumentation technology are to further develop systems packaging and component testing of specialized sensors, further develop instrumentation techniques on complex surfaces, improve sensor durability, and to address needs for extreme temperature applications. The technology research and development ongoing at NASA Glenn for applications to future launch vehicles, space vehicles, and ground systems is outlined.

Wrbanek, John D.; Fralick, Gustave C.

2006-01-01

357

DEVELOPMENT OF NOVEL CERAMIC NANOFILM-FIBER INTEGRATED OPTICAL SENSORS FOR RAPID DETECTION OF COAL DERIVED SYNTHESIS GAS  

SciTech Connect

The overall goal of this project is to conduct fundamental studies on advanced ceramic materials and fiber optic devices for developing new types of high temperature (>500{degree}C) fiber optic chemical sensors (FOCS) for monitoring fossil (mainly coal) and biomass derived gases in power plants. The primary technical objective is to investigate and demonstrate the nanocrystalline doped-ceramic thin film enabled FOCS that possess desired stability, sensitivity and selectivity for in-situ, rapid gas detection in the syngas streams from gasification and combustion flue gases. This report summarizes research works of two integrated parts: (1) development of metal oxide solid thin films as sensing materials for detection and measurement of important gas components relevant to the coal- and biomass-derived syngas and combustion gas streams at high temperatures; and (2) development of fiber optic devices that are potentially useful for constructing FOCS in combination with the solid oxide thin films identified in this program.

Junhang Dong; Hai Xiao; Xiling Tang; Hongmin Jiang; Kurtis Remmel; Amardeep Kaur

2012-09-30

358

Hybrid AlGaN/GaN-ZnO-nanowire gas sensors.  

PubMed

The potential of AIGaN/GaN heterostructures integrated with zinc oxide (ZnO) nanowires for gas sensing applications is demonstrated. Single crystal ZnO nanowires, serving as sensing probes, were selectively grown between two ohmic electrodes of AIGaN/GaN two dimensional electron gas heterostructures by thermal oxidation of sputtered zinc films in air. Electron diffraction and transmission electron microscopy showed the ZnO-nanowires to be crystalline structures oriented in the [001] direction. The fabricated structures were used to detect ethanol, acetone and methanol in a nitrogen background. The results indicate that the hybrid AIGaN/GaN-ZnO nanowires gas sensors are operable over a broad range of temperatures and could potentially be integrated with devices for wireless environmental monitoring. PMID:21780389

Zahmani, Abdeldjelil Habib; Sandhu, Adarsh

2011-05-01

359

Highly sensitive and selective WO3 nanoparticle gas sensor operating in thermally modulated dynamic mode  

NASA Astrophysics Data System (ADS)

Nanoparticle films of crystalline WO3, designed for gas sensing applications, were deposited on alumina substrates by reactive gas deposition. H2S, ethanol vapour, and binary mixtures of ethanol/H2S, ethanol/NO2 and H2S/NO2 were used in different concentrations for testing the performance of the sensor device. The sensor was operated in dynamic mode by modulating its temperature between 150 and 250 °C. Coefficients were extracted by applying Fast Fourier Transform (FFT) and Discrete Wavelet Transform (DWT) methods to the dynamic resistance response of the sensor. These coefficients were then used as inputs for pattern recognition methods to extract both quantitative (concentration) and qualitative (chemical selectivity) information about the test gases. After sensor calibration, it was possible to detect as little as 200 ppb of ethanol and 20 ppb of H2S with good accuracy. Furthermore, ethanol and H2S could be detected with good sensitivity and selectivity in the presence of both reducing and oxidising gases.

Ionescu, Radu; Hoel, Anders; Granqvist, Claes-Goran; Llobet, Eduard; Heszler, Peter

2004-05-01

360

Processing and Gas Barrier Behavior of Multilayer Thin Nanocomposite Films  

E-print Network

Thin films with the ability to impart oxygen and other types of gas barrier are crucial to commercial packaging applications. Commodity polymers, such as polyethylene (PE), polycarbonate (PC) and polyethylene terephthalate (PET), have insufficient...

Yang, You-Hao

2012-10-19

361

Specific and reproducible gas sensors utilizing gas-phase chemical reaction on organic transistors.  

PubMed

Utilizing a textbook reaction on the surface of an organic active channel, achieves sensitive detection of HCl, NH3 and NO2, with good selectivity, excellent reproducibility, and satisfactory stability. These results reveal gas-phase reaction assisted detection as a unique and promising approach to construct practical applicable gas sensors with typical organic transistors. PMID:24510689

Zang, Yaping; Zhang, Fengjiao; Huang, Dazhen; Di, Chong-an; Meng, Qing; Gao, Xike; Zhu, Daoben

2014-05-01

362

Engineered doped and codoped polyaniline gas sensors synthesized in N,N,dimethylformamide media  

NASA Astrophysics Data System (ADS)

Conducting Polyaniline films (Pani) on Corning glass substrates, produced using either an in-situ doping process or a co-doping process, were prepared by the oxidative polymerization of aniline in N,N,dimethylformamide. Bicyclic aliphatic camphorsulfonic acid (CSA), aromatic toluenesulfonic acid (TSA) and carboxylic trifluoroacetic acid (TFA) were employed as doping agents, and CSA mixed with TSA and CSA mixed with TFA were employed as the co-doping materials. The topography of the Pani films was analyzed by atomic-force microscopy (AFM), and their doping and oxidizing states were characterized by Fourier-transform infrared (FT-IR) spectroscopy and optical (UV-Vis) spectroscopy. Flower-like clusters, microfibers, and nanofibers were obtained by doping with CSA, TSA, and the mix of both (CSATSA), respectively. The flower-like morphology limits the conductivity of the film while the microfiber morphology leads to a highly conductive film. The conductivity of the films increases with the doping level, coil-like conformation of the chain and the protonation of the imine in quinoid units. The codoped process reduces the roughness of the CSA-doped films by 50%, but the conductivity depends on the acid type used for this process (TSA or TFA). The optical gas sensor response of the films is related to both the morphology and the degree of protonation. In this study, Pani with a microfiber morphology obtained from TSA-doping is the most sensitive to ammonia gas sensing, and Pani with flower-like morphology is the least sensitive.

Arenas, M. C.; Sánchez, Gabriela; Nicho, M. E.; Elizalde-Torres, Josefina; Castaño, V. M.

2012-03-01

363

Quantifying gas sensor and delivery system response time using GC\\/MS  

Microsoft Academic Search

Semiconducting metal oxide (SMO) chemiresistive sensors have applications for gas detection in chemical, biological, medical and environmental fields. We examine how properties of the sensor test system can introduce errors into measurements of sensitivity, reproducibility and response time of SMO sensors. We describe and characterize the performance of a typical gas delivery system using a gas chromatograph\\/quadruple mass spectrometer (GC\\/MS)

R. S. Pilling; G. Bernhardt; C. S. Kim; J. Duncan; C. B. H. Crothers; D. Kleinschmidt; D. J. Frankel; R. J. Lad; B. G. Frederick

2003-01-01

364

Methods for gas detection using stationary hyperspectral imaging sensors  

DOEpatents

According to one embodiment, a method comprises producing a first hyperspectral imaging (HSI) data cube of a location at a first time using data from a HSI sensor; producing a second HSI data cube of the same location at a second time using data from the HSI sensor; subtracting on a pixel-by-pixel basis the second HSI data cube from the first HSI data cube to produce a raw difference cube; calibrating the raw difference cube to produce a calibrated raw difference cube; selecting at least one desired spectral band based on a gas of interest; producing a detection image based on the at least one selected spectral band and the calibrated raw difference cube; examining the detection image to determine presence of the gas of interest; and outputting a result of the examination. Other methods, systems, and computer program products for detecting the presence of a gas are also described.

Conger, James L. (San Ramon, CA); Henderson, John R. (Castro Valley, CA)

2012-04-24

365

Optical Sensors Based on Single on Arm Thin Film Waveguide Interferometer  

NASA Technical Reports Server (NTRS)

Single-arm dual-mode optical waveguide interferometer utilizes interference between two modes of different order. Sensing effect results from the change in propagation conditions of the modes caused by the environment. The waveguide is made as an open asymmetric structure containing a dye-doped polymer film onto a 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)/TE(sub 1) or TM(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 targeting a particular gaseous reagent. Change of the optical absorption spectrum of the dye caused by the gaseous pollutant results in change of the reactive index of the dye-doped polymer film that can be detected by the sensor. As indicator dyes we utilize Bromocresol Purple doped into polymer poly(methyl) methacrylate that is sensitive to small concentrations of ammonia. The indicator dye demonstrated an irreversible increase in optical absorption near the peak at 350 nm being exposed to 5% ammonia in pure nitrogen at 600 Torr. The dye also showed reversible growth of the absorption peak near 600 nm after exposure to a vapor of standard medical ammonia spirit (65% alcohol). 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 a sensitivity to temperature change of the order of 2 C per 2pi phase shift. The sensitivity of the sensor to the presence of dTy ammonia is not less than 300 ppm per 2pi phase shift. The proposed sensor can be used as a robust stand-alone instrument for continuous environment pollution monitoring.

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

2000-01-01

366

Oxide film deposition by Gas-Cluster ion assisted deposition  

SciTech Connect

The development of ultra-high quality (UHQ) films is in progress under the NEDO projects. This project is a collaboration between several companies, national laboratories and universities. A Multi-Beam Gas-Cluster Ion Beam System has been developed for fabricating indium tin oxide (ITO) films. The concept of a multi-beam deposition technique, the description of the Multi-Beam Gas Cluster Ion Beam System as well as our current progress on this project are presented.

Murai, K.; Tamura, S.; Kiuchi, M.; Umesaki, N.; Minami, E.; Matsuo, J.; Yamada, I. [Osaka National Research Institute, AIST, MITI, Ikeda, Osaka 563-8577 (Japan); Ion Beam Engineering Experimental Laboratory, Kyoto University, Sakyo, Kyoto, 606-8501 (Japan)

1999-06-10

367

Chemical Discrimination in Turbulent Gas Mixtures with MOX Sensors Validated by Gas Chromatography-Mass Spectrometry  

PubMed Central

Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance. PMID:25325339

Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

2014-01-01

368

Electromagnetic Wave Shield Effect of Touch-Panel-Sensor Using Resistive Films  

NASA Astrophysics Data System (ADS)

A touch-panel sensor structure with a electromagnetic wave shield effect has been realized. In this paper, the electromagnetic wave effect and optical transmittance were analyzed for a sensor with ITO(Indium Tin Oxide) resistive transparent films. In the result, touch-panel sensor structure with the electromagnetic wave shield effect of 26dB were obtained.

Harada, Nozomu

369

Electromagnetic Wave Shield Effect of Touch-Panel-Sensor Using Resistive Films  

Microsoft Academic Search

A touch-panel sensor structure with a electromagnetic wave shield effect has been realized. In this paper, the electromagnetic wave effect and optical transmittance were analyzed for a sensor with ITO(Indium Tin Oxide) resistive transparent films. In the result, touch-panel sensor structure with the electromagnetic wave shield effect of 26dB were obtained.

Nozomu Harada

2008-01-01

370

Gas sensing properties of very thin TiO2 films prepared by atomic layer deposition (ALD)  

NASA Astrophysics Data System (ADS)

Very thin titanium dioxide (TiO2) films of less than 10 nm were deposited by atomic layer deposition (ALD) in order to study their gas sensing properties. Applying the quartz crystal microbalance (QCM) method, prototype structures with the TiO2 ALD deposited thin films were tested for sensitivity to NO2. Although being very thin, the films were sensitive at room temperature and could register low concentrations as 50-100 ppm. The sorption is fully reversible and the films seem to be capable to detect for long term. These initial results for very thin ALD deposited TiO2 films give a promising approach for producing gas sensors working at room temperature on a fast, simple and cost-effective technology.

Boyadjiev, S.; Georgieva, V.; Vergov, L.; Baji, Zs; Gáber, F.; Szilágyi, I. M.

2014-11-01

371

Fiber-Optic Temperature Sensor Using a Thin-Film Fabry-Perot Interferometer  

NASA Technical Reports Server (NTRS)

A fiber-optic temperature sensor was developed that is rugged, compact, stable, and can be inexpensively fabricated. This thin-film interferometric temperature sensor was shown to be capable of providing a +/- 2 C accuracy over the range of -55 to 275 C, throughout a 5000 hr operating life. A temperature-sensitive thin-film Fabry-Perot interferometer can be deposited directly onto the end of a multimode optical fiber. This batch-fabricatable sensor can be manufactured at a much lower cost than can a presently available sensor, which requires the mechanical attachment of a Fabry-Perot interferometer to a fiber. The principal disadvantage of the thin-film sensor is its inherent instability, due to the low processing temperatures that must be used to prevent degradation of the optical fiber's buffer coating. The design of the stable thin-film temperature sensor considered the potential sources of both short and long term drifts. The temperature- sensitive Fabry-Perot interferometer was a silicon film with a thickness of approx. 2 microns. A laser-annealing process was developed which crystallized the silicon film without damaging the optical fiber. The silicon film was encapsulated with a thin layer of Si3N4 over coated with aluminum. Crystallization of the silicon and its encapsulation with a highly stable, impermeable thin-film structure were essential steps in producing a sensor with the required long-term stability.

Beheim, Glenn

1997-01-01

372

Compressive hyperspectral sensor for LWIR gas detection  

NASA Astrophysics Data System (ADS)

Focal plane arrays with associated electronics and cooling are a substantial portion of the cost, complexity, size, weight, and power requirements of Long-Wave IR (LWIR) imagers. Hyperspectral LWIR imagers add significant data volume burden as they collect a high-resolution spectrum at each pixel. We report here on a LWIR Hyperspectral Sensor that applies Compressive Sensing (CS) in order to achieve benefits in these areas. The sensor applies single-pixel detection technology demonstrated by Rice University. The single-pixel approach uses a Digital Micro-mirror Device (DMD) to reflect and multiplex the light from a random assortment of pixels onto the detector. This is repeated for a number of measurements much less than the total number of scene pixels. We have extended this architecture to hyperspectral LWIR sensing by inserting a Fabry-Perot spectrometer in the optical path. This compressive hyperspectral imager collects all three dimensions on a single detection element, greatly reducing the size, weight and power requirements of the system relative to traditional approaches, while also reducing data volume. The CS architecture also supports innovative adaptive approaches to sensing, as the DMD device allows control over the selection of spatial scene pixels to be multiplexed on the detector. We are applying this advantage to the detection of plume gases, by adaptively locating and concentrating target energy. A key challenge in this system is the diffraction loss produce by the DMD in the LWIR. We report the results of testing DMD operation in the LWIR, as well as system spatial and spectral performance.

Russell, Thomas A.; McMackin, Lenore; Bridge, Bob; Baraniuk, Richard

2012-06-01

373

Gas Sensor Evaluations in Polymer Combustion Product Atmospheres  

NASA Technical Reports Server (NTRS)

Toxic gases produced by the combustion or thermo-oxidative degradation of materials such as wire insulation, foam, plastics, or electronic circuit boards in space shuttle or space station crew cabins may pose a significant hazard to the flight crew. Toxic gas sensors are routinely evaluated in pure gas standard mixtures, but the possible interferences from polymer combustion products are not routinely evaluated. The NASA White Sands Test Facility (WSTF) has developed a test system that provides atmospheres containing predetermined quantities of target gases combined with the coincidental combustion products of common spacecraft materials. The target gases are quantitated in real time by infrared (IR) spectroscopy and verified by grab samples. The sensor responses are recorded in real time and are compared to the IR and validation analyses. Target gases such as carbon monoxide, hydrogen cyanide, hydrogen chloride, and hydrogen fluoride can be generated by the combustion of poly(vinyl chloride), polyimide-fluoropolymer wire insulation, polyurethane foam, or electronic circuit board materials. The kinetics and product identifications for the combustion of the various materials were determined by thermogravimetric-IR spectroscopic studies. These data were then scaled to provide the required levels of target gases in the sensor evaluation system. Multisensor toxic gas monitors from two manufacturers were evaluated using this system. In general, the sensor responses satisfactorily tracked the real-time concentrations of toxic gases in a dynamic mixture. Interferences from a number of organic combustion products including acetaldehyde and bisphenol-A were minimal. Hydrogen bromide in the products of circuit board combustion registered as hydrogen chloride. The use of actual polymer combustion atmospheres for the evaluation of sensors can provide additional confidence in the reliability of the sensor response.

Delgado, Rafael H.; Davis, Dennis D.; Beeson, Harold D.

1999-01-01

374

Electrocatalytic cermet gas detector/sensor  

DOEpatents

An electrocatalytic device for sensing gases is described. The gas sensing device includes a substrate layer, a reference electrode disposed on the substrate layer comprised of a nonstoichiometric chemical compound enabling oxygen diffusion therethrough, a lower reference electrode coupled to the reference electrode, a solid electrolyte coupled to the lower reference electrode and an upper catalytically active electrode coupled to the solid electrolyte. 41 figs.

Vogt, M.C.; Shoemarker, E.L.; Fraioli, A.V.

1995-07-04

375

Selectivity enhancement of metal oxide gas sensors using a micromachined gas chromatographic column  

Microsoft Academic Search

Indoor air quality monitoring applications require both high sensitivity and selectivity, which are difficult to reach with solid state gas sensors. While for some gas species like, e.g. CO and NO2, the use of optimized operating conditions allows to reach the necessary selectivity, the discrimination between single volatile organic compounds (VOC) is generally not possible with stand-alone arrays of gas

S. Zampolli; I. Elmi; J. Stürmann; S. Nicoletti; L. Dori; G. C. Cardinali

2005-01-01

376

The effect of carbon nanotube dispersion on CO gas sensing characteristics of polyaniline gas sensor.  

PubMed

Polyaniline is one of the most promising conducting polymers for gas sensing applications due to its relatively high stability and n or p type doping capability. However, the conventionally doped polyaniline still exhibits relatively high resistivity, which causes difficulty in gas sensing measurement. In this work, the effect of carbon nanotube (CNT) dispersion on CO gas sensing characteristics of polyaniline gas sensor is studied. The carbon nanotube was synthesized by Chemical Vapor Deposition (CVD) using acetylene and argon gases at 600 degrees C. The Maleic acid doped Emeradine based polyaniline was synthesized by chemical polymerization of aniline. CNT was then added and dispersed in the solution by ultrasonication and deposited on to interdigitated AI electrode by solvent casting. The sensors were tested for CO sensing at room temperature with CO concentrations in the range of 100-1000 ppm. It was found that the gas sensing characteristics of polyaniline based gas sensor were considerably improved with the inclusion of CNT in polyaniline. The sensitivity was increased and response/recovery times were reduced by more than the factor of 2. The results, therefore, suggest that the inclusion of CNT in MA-doped polyaniline is a promising method for achieving a conductive polymer gas sensor with good sensitivity, fast response, low-concentration detection and room-operating-temperature capability. PMID:17256348

Wanna, Y; Srisukhumbowornchai, N; Tuantranont, A; Wisitsoraat, A; Thavarungkul, N; Singjai, P

2006-12-01

377

Novel diode laser-based sensors for gas sensing applications  

NASA Technical Reports Server (NTRS)

The development of compact spectroscopic gas sensors and their applications to environmental sensing will be described. These sensors employ mid-infrared difference-frequency generation (DFG) in periodically poled lithium niobate (PPLN) crystals pumped by two single-frequency solid state lasers such as diode lasers, diode-pumped solid state, and fiber lasers. Ultrasensitive, highly selective, and real-time measurements of several important atmospheric trace gases, including carbon monoxide, nitrous oxide, carbon dioxide, formaldehyde [correction of formaldehye], and methane, have been demonstrated.

Tittel, F. K.; Lancaster, D. G.; Richter, D.

2000-01-01

378

Bedside arterial blood gas monitoring system using fluorescent optical sensors  

NASA Astrophysics Data System (ADS)

We describe a bedside arterial blood gas (ABG) monitoring system which uses fluorescent optical sensors in the measurement of blood pH, PCO2 and PO2. The Point-of-Care Arterial Blood Gas Monitoring System consists of the SensiCathTM optical sensor unit manufactured by Optical Sensors Incorporated and the TramTM Critical Care Monitoring System with ABG Module manufactured by Marquette Electronics Incorporated. Current blood gas measurement techniques require a blood sample to be removed from the patient and transported to an electrochemical analyzer for analysis. The ABG system does not require removal of blood from the patient or transport of the sample. The sensor is added to the patient's existing arterial line. ABG measurements are made by drawing a small blood sample from the arterial line in sufficient quantity to ensure an undiluted sample at the sensor. Measurements of pH, PCO2 and PO2 are made within 60 seconds. The blood is then returned to the patient, the line flushed and results appear on the bedside monitor. The ABG system offers several advantages over traditional electrochemical analyzers. Since the arterial line remains closed during the blood sampling procedure the patient's risk of infection is reduced and the caregiver's exposure to blood is eliminated. The single-use, disposable sensor can be measure 100 blood samples over 72 hours after a single two-point calibration. Quality Assurance checks are also available and provide the caregiver the ability to assess system performance even after the sensor is patient attached. The ABG module integrates with an existing bedside monitoring system. This allows ABG results to appear on the same display as ECG, respiration, blood pressure, cardiac output, SpO2, and other clinical information. The small module takes up little space in the crowded intensive care unit. Performance studies compare the ABG system with an electrochemical blood gas analyzer. Study results demonstrated accurate and precise blood gas measurement of 100 samples and 72 hour performance without need for re-calibration.

Bartnik, Daniel J.; Rymut, Russell A.

1995-05-01

379

Investigation of gas-sensitivity of sensor structures to carbon monoxide in a wide range of temperature, concentration and humidity of gas medium  

Microsoft Academic Search

Response to CO of seven sensor structures of SnO2 with various catalytic additives, made by thick-film technology, was investigated in a dry gas medium at a concentration of 200ppm CO in a temperature range of 100–600°C. Concentration dependence of four sensors (pure SnO2 and doped with three catalytic additives: 3% La2O3, 1% Sb2O5+3% La2O3 and 1% Pt+3% Pd) was investigated

V. V. Malyshev; A. V. Pislyakov

2007-01-01

380

Development of sweep gas sensor with proton conduction  

SciTech Connect

To obtain engineering data for a design of a fusion blanket, a program in which a mock-up simulating a blanket structure is irradiated is proceeded in the JMTR (Japan Materials Tasting Reactor) project. It is indispensable for this irradiation test to purge the tritium produced in the mock-up by the sweep gas and to measure the tritium concentration in the sweep gas on line. However, the bad effects such as tritium adsorption on the inner surface of the pipe and tritium diffusion from the pipe are apprehended, because the distance between the mock-up and an ionization chamber is about 20m long. Therefore, it is necessary to develop a sweep gas sensor which can measure the tritium concentration in the mock-up directly without the above apprehension. A sweep gas sensor had been fabricated on trial and several performance tests were carried out. From the results of the tests, it was found that this sensor could be used at the atmosphere of high temperature of 600-700{degree}C and had good response. 7 refs., 7 figs., 1 tab.

Sagawa, Hisashi; Kawamura, Hiroshi; Oyamada, Rokuro [Japan Atomic Energy Research Inst., Ibaraki (Japan); Miura, Kuniaki [Sukegawa Electric Co., LTD., Ibaraki (Japan)

1995-10-01

381

On optimization of sensor selection for aircraft gas turbine engines Ramgopal Mushini  

E-print Network

sets for the problem of aircraft gas turbine engine health parameter estimation. The performance metricOn optimization of sensor selection for aircraft gas turbine engines Ramgopal Mushini Cleveland for generating an optimal sensor set [3]. 3. Aircraft gas turbine engines An aircraft gas turbine engine

Simon, Dan

382

Flammable and noxious gas sensing using a microtripolar electrode sensor with diameter and chirality sorted single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We report on the utilization of densely packed (˜10 SWCNTs µm-1), well-aligned arrays of single-chirality single-walled carbon nanotubes (SWCNTs) as an effective thin-film for integration into a gas sensor with a microtripolar electrode, based on field ionization by dielectrophoretic assembly from a monodisperse SWCNTs solution obtained by polymer-mediated sorting. The sensor is characterized as a field ionization electrode with sorted SWCNTs acting as both the sensing material and transducer gas concentrated directly into an electrical signal, an extractor serving to improve electric field uniformity and a collector electrode completing the current path. The gas sensing properties toward flammable and noxious gases, such as CO and H2, were investigated at room temperature. Besides the high sensitivity, the as-fabricated sensor exhibited attractive behaviors in terms of both the detection limit and a fast response, suggesting that our sensor could be used to partly circumvent the low sensing selectivity, long recovery time or irreversibility and allow for a preferential identification of the selected flammable and noxious analytes. Interestingly, the excellent sensing behaviors of the sensors based on the field ionization effect derive directly from the combined effects of the high-quality, low defect SWCNTs arrays, which leads to a small device-to-device variation in the properties and the optimization of electrode fabrication, highlighting the sensor as an appealing candidate in view of nanotube electronics.

Cai, Shengbing; Duan, Zhe min; Zhang, Yong

2013-08-01

383

Varying potential silicon carbide gas sensor  

NASA Technical Reports Server (NTRS)

A hydrocarbon gas detection device operates by dissociating or electro-chemically oxidizing hydrocarbons adsorbed to a silicon carbide detection layer. Dissociation or oxidation are driven by a varying potential applied to the detection layer. Different hydrocarbon species undergo reaction at different applied potentials so that the device is able to discriminate among various hydrocarbon species. The device can operate at temperatures between 100.degree. C. and at least 650.degree. C., allowing hydrocarbon detection in hot exhaust gases. The dissociation reaction is detected either as a change in a capacitor or, preferably, as a change of current flow through an FET which incorporates the silicon carbide detection layers. The silicon carbide detection layer can be augmented with a pad of catalytic material which provides a signal without an applied potential. Comparisons between the catalytically produced signal and the varying potential produced signal may further help identify the hydrocarbon present.

Shields, Virgil B. (Inventor); Ryan, Margaret A. (Inventor); Williams, Roger M. (Inventor)

1997-01-01

384

Sensor and Actuator Needs for More Intelligent Gas Turbine Engines  

NASA Technical Reports Server (NTRS)

This paper provides an overview of the controls and diagnostics technologies, that are seen as critical for more intelligent gas turbine engines (GTE), with an emphasis on the sensor and actuator technologies that need to be developed for the controls and diagnostics implementation. The objective of the paper is to help the "Customers" of advanced technologies, defense acquisition and aerospace research agencies, understand the state-of-the-art of intelligent GTE technologies, and help the "Researchers" and "Technology Developers" for GTE sensors and actuators identify what technologies need to be developed to enable the "Intelligent GTE" concepts and focus their research efforts on closing the technology gap. To keep the effort manageable, the focus of the paper is on "On-Board Intelligence" to enable safe and efficient operation of the engine over its life time, with an emphasis on gas path performance

Garg, Sanjay; Schadow, Klaus; Horn, Wolfgang; Pfoertner, Hugo; Stiharu, Ion

2010-01-01

385

Novel Gas Sensors for High-Temperature Fossil Fuel Applications  

SciTech Connect

SRI International (SRI) is developing ceramic-based microsensors to detect exhaust gases such as NO, NO{sub 2}, and CO in advanced combustion and gasification systems under this DOE NETL-sponsored research project. The sensors detect the electrochemical activity of the exhaust gas species on catalytic electrodes attached to a solid state electrolyte and are designed to operate at the high temperatures, elevated pressures, and corrosive environments typical of large power generation exhausts. The sensors can be easily integrated into online monitoring systems for active emission control. The ultimate objective is to develop sensors for multiple gas detection in a single package, along with data acquisition and control software and hardware, so that the information can be used for closed-loop control in novel advanced power generation systems. This report details the Phase I Proof-of-Concept, research activities performed from October 2003 to March 2005. SRI's research work includes synthesis of catalytic materials, sensor design and fabrication, software development, and demonstration of pulse voltammetric analysis of NO, NO{sub 2}, and CO gases on catalytic electrodes.

Palitha Jayaweera; Francis Tanzella

2005-03-01

386

Low-Cost Gas Sensors Produced by the Graphite Line-Patterning Technique Applied to Monitoring Banana Ripeness  

PubMed Central

A low-cost sensor array system for banana ripeness monitoring is presented. The sensors are constructed by employing a graphite line-patterning technique (LPT) to print interdigitated graphite electrodes on tracing paper and then coating the printed area with a thin film of polyaniline (PANI) by in-situ polymerization as the gas-sensitive layer. The PANI layers were used for the detection of volatile organic compounds (VOCs), including ethylene, emitted during ripening. The influence of the various acid dopants, hydrochloric acid (HCl), methanesulfonic acid (MSA), p-toluenesulfonic acid (TSA) and camphorsulfonic acid (CSA), on the electrical properties of the thin film of PANI adsorbed on the electrodes was also studied. The extent of doping of the films was investigated by UV-Vis absorption spectroscopy and tests showed that the type of dopant plays an important role in the performance of these low-cost sensors. The array of three sensors, without the PANI-HCl sensor, was able to produce a distinct pattern of signals, taken as a signature (fingerprint) that can be used to characterize bananas ripeness. PMID:22163963

Manzoli, Alexandra; Steffens, Clarice; Paschoalin, Rafaella T.; Correa, Alessandra A.; Alves, William F.; Leite, Fábio L.; Herrmann, Paulo S. P.

2011-01-01

387

Sensitive ammonia gas sensors fabricated using biologically assembled copper sulfide  

NASA Astrophysics Data System (ADS)

Copper sulfide-based ammonia (NH3) gas sensors were assembled using a genetically modified viral template. Glutamic acid residues on the filament-shaped bioscaffold surface facilitated the synthesis of nanocrystalline Cu1.8S. Each device comprised a network of biological materials decorated with a nonstoichiometric semiconductor. These chemiresistive devices had high sensitivity to NH3 concentrations from 10 to 80 ppm under room-temperature operation. Response times greater than 15 min were observed. These results demonstrate the potential of biotemplated materials for sensitive gas detection at room temperature.

Shahriar Zaman, Mohammed; Moon, Chung Hee; Haberer, Elaine D.

2014-11-01

388

Thin-film chemical sensors based on electron tunneling  

NASA Technical Reports Server (NTRS)

The physical mechanisms underlying a novel chemical sensor based on electron tunneling in metal-insulator-metal (MIM) tunnel junctions were studied. Chemical sensors based on electron tunneling were shown to be sensitive to a variety of substances that include iodine, mercury, bismuth, ethylenedibromide, and ethylenedichloride. A sensitivity of 13 parts per billion of iodine dissolved in hexane was demonstrated. The physical mechanisms involved in the chemical sensitivity of these devices were determined to be the chemical alteration of the surface electronic structure of the top metal electrode in the MIM structure. In addition, electroreflectance spectroscopy (ERS) was studied as a complementary surface-sensitive technique. ERS was shown to be sensitive to both iodine and mercury. Electrolyte electroreflectance and solid-state MIM electroreflectance revealed qualitatively the same chemical response. A modified thin-film structure was also studied in which a chemically active layer was introduced at the top Metal-Insulator interface of the MIM devices. Cobalt phthalocyanine was used for the chemically active layer in this study. Devices modified in this way were shown to be sensitive to iodine and nitrogen dioxide. The chemical sensitivity of the modified structure was due to conductance changes in the active layer.

Khanna, S. K.; Lambe, J.; Leduc, H. G.; Thakoor, A. P.

1985-01-01

389

Effect of tear film break-up on higher-order aberrations measured with wavefront sensor  

Microsoft Academic Search

PURPOSE: To investigate whether optical wavefront aberrations vary with tear film break-up.DESIGN: Observational case series.METHODS: Higher-order aberrations were examined for 20 eyes of 20 normal subjects with a Hartmann-Shack wavefront sensor before and after tear film break-up.RESULTS: Higher-order aberrations for photopic vision (central 4 mm diameter) after tear film break-up increased 1.44 fold compared to higher-order aberrations before tear film

Shizuka Koh; Naoyuki Maeda; Teruhito Kuroda; Yuichi Hori; Hitoshi Watanabe; Takashi Fujikado; Yasuo Tano; Yoko Hirohara; Toshifumi Mihashi

2002-01-01

390

Optical Breath Gas Sensor for Extravehicular Activity Application  

NASA Technical Reports Server (NTRS)

The function of the infrared gas transducer used during extravehicular activity in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation portable life support system (PLSS) requires next generation CO2 sensing technology with performance beyond that presently in use on the Space Shuttle/International Space Station extravehicular mobility unit (EMU). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode spectrometer based on wavelength modulation spectroscopy is being developed for this purpose by Vista Photonics, Inc. Two prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The sensors incorporate a laser diode-based CO2 channel that also includes an incidental water vapor (humidity) measurement and a separate oxygen channel using a vertical cavity surface emitting laser. Both prototypes are controlled digitally with a field-programmable gate array/microcontroller architecture. The present development extends and upgrades the earlier hardware to the Advanced PLSS 2.0 test article being constructed and tested at JSC. Various improvements to the electronics and gas sampling are being advanced by this project. The combination of low power electronics with the performance of a long wavelength laser spectrometer enables multi-gas sensors with significantly increased performance over that presently offered in the EMU.

Wood, William R.; Casias, Miguel E.; Vakhtin, Andrei B.; Pilgrim, Jeffrey S.; Chullen, Cinda; Falconi, Eric A.; McMillin, Summer

2013-01-01

391

Gas Sensing Properties of bis-Phthalocyanine Thin Film  

NASA Astrophysics Data System (ADS)

In this study, response of the cofacial bis- phthalocyanine film to vapor of Volatile Organic Compounds (VOCs) was investigated. Test gases were vapors of acetone, toluene, ethanol and ammonia. Measurements were carried out between the temperatures of 293 K-423 K. Bis-phthalocyanine was dissolved in chloroform. Thin film of bis-phthalocyanine was deposited by spraying method on glass substrate patterned with Interdigital Transducer (IDT). During the measurements 0.5 volts were applied to the IDT. Response characteristics of the film were determined by means of change in dc conductivity as a function of gas concentration and temperature. Gas concentrations were controlled by mass flow controller. Dry nitrogen was used as carrier gas. Vapor pressure of the VOCs was calculated using Antoine equation. Response characteristics of the film were determined in a wide range of gas concentration (0.25%-18%). The film showed good sensitivity to the VOCs vapors in the measurement range. The responses of the film were reversible. All the measurement system was computerized.

Dumludag, Fatih; Kilic, Pinar; Odabas, Zafer; Altindal, Ahmet; Bekaroglu, Ozer

2010-01-01

392

Nano particle porous alumina based thin film parallel plate capacitive humidity sensor  

NASA Astrophysics Data System (ADS)

A Relative humidity sensor was fabricated based on porous thin film of ?-Al2O3 formed between the parallel Pd/Ag electrodes working on capacitive technique. The film was fabricated by dip coating of sol solution obtained from the sol-gel method. The electrical parameters of the sensor have been determined by Agilent 4294A impedance analyzer. The sensor so obtained is found to be sensitive in 10 to 90% RH. The response time of the sensor is very low around 24 seconds and recovery time 40 seconds.

Kumar, Shailesh

2014-04-01

393

Nanostructure-engineered chemical sensors for hazardous gas and vapor detection  

NASA Astrophysics Data System (ADS)

A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs) and metal oxides nanowires or nanobelts, on a pair of interdigitated electrodes (IDE) processed with a siliconbased microfabrication and micromachining technique. The IDE fingers were fabricated using thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to hazardous gases and vapors, such as acetone, benzene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing in our sensor platform can be understood by electron modulation between the nanostructure engineered device and gas molecules. As a result of the electron modulation, the conductance of nanodevice will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost.

Li, Jing; Lu, Yijiang

2004-12-01

394

Formation, characterization, and flow dynamics of nanostructure modified sensitive and selective gas sensors based on porous silicon  

NASA Astrophysics Data System (ADS)

Nanopore covered microporous silicon interfaces have been formed via an electrochemical etch for gas sensor applications. Rapid reversible and sensitive gas sensors have been fabricated. Both top-down and bottom-up approaches are utilized in the process. A nano-pore coated micro-porous silicon surface is modified selectively for sub-ppm detection of NH3, PH3 , NO, H2S, SO2. The selective depositions include electrolessly generated SnO2, CuxO, Au xO, NiO, and nanoparticles such as TiO2, MgO doped TiO 2, Al2O3, and ZrO2. Flow dynamics are analyzed via numerical simulations and response data. An array of sensors is formed to analyze mixed gas response. A general coating selection method for chemical sensors is established via an extrapolation on the inverse of the Hard-Soft Acid-Base concept. In Chapter 1, the current state of the porous silicon gas sensor research is reviewed. Since metal oxide thin films, and, recently, nanowires are dominantly used for sensing application, the general properties of metal oxides are also discussed in this chapter. This chapter is concluded with a discussion about commercial gas sensors and the advantages of using porous silicon as a sensing material. The PS review discussed at the beginning of this chapter is an overview of the following publication: (1) "The Potential of Porous Silicon Gas Sensors", Serdar Ozdemir, James L. Gole, Current Opinion in Solid State and Materials Science, 11, 92-100 (2007). In Chapter 2, porous silicon formation is explained in detail. Interesting results of various silicon anodization experiments are discussed. In the second part of this chapter, the microfabrication process of porous silicon conductometric gas sensors and gas testing set up are briefly introduced. In chapter 3, metal oxide nanoparticle/nanocluster formation and characterization experiments via SEM and XPS analysis are discussed. Chapter 4 is an overview of the test results for various concentrations NH3, NO, NO2 and PH3. The interaction strengths between the test gases and various nanoparticles on porous silicon are measured. The flow dynamics in the micro- and nanoporous regime is analyzed by using experimental response data and numerical simulations. The results in this chapter are partially published in the following articles: (1) "Porous Silicon Gas Sensors for Room Temperature Detection of Ammonia and Phosphine ", 214th Meeting of ECS: Honolulu, Hawaii Oct 12-17, 2008, S. Ozdemir, J.L. Gole, ECS Trans. 16 (11), 379 (2008). (2) "A Phosphine Detection Matrix Using Porous Silicon Gas Sensors" S. Ozdemir, J.L. Gole, Sensors and Actuators B, 151, 274-280 (2010). (3) "A Nanostructure Modified Porous Silicon Gas Sensor Detection Matrix for NO with Demonstration of the Transient Conversion of NO to NO2", Serdar Ozdemir, Thomas B. Osburn, James L. Gole, submitted to Journal of Electrochemical Society. (4) "Selectivity Improvement and Response Time Scale of Porous Silicon Conductometric Gas Sensors" S. Ozdemir, J. L. Gole, ECS Transactions, Volume 33, Issue 8, pg 111-115. In chapter 5, a model is proposed for selectivity improvements in PS gas sensors based on Inverse of Hard Soft Acid Base interactions. An extended version of this chapter is published in the following publication: (1) " Nanostructure directed physisorption vs. chemisorption at semiconductor interfaces: the inverse of the hard-soft acid-base (HSAB) concept", J.L.Gole, S. Ozdemir, ChemPhysChem, 11, 2573.2581 (2010). Chapter 6 is a brief conclusion of the results discussed in this thesis.

Ozdemir, Serdar

395

Discontinuously Operated Metal Oxide Gas Sensors for Flexible Tag Microlab Applications  

Microsoft Academic Search

Micromachined silicon substrates have significantly reduced the heating power consumption of metal oxide (MOX) gas sensors. Specific applications, however, require further reductions far beyond the present state-of-the-art. In this paper, we report on discontinuously operated MOX gas sensors on micromachined heater platforms and show that such sensors allow power consumption levels to be reached which are consistent with Flexible Tag

Ilker Sayhan; Andreas Helwig; Thomas Becker; Gerhard Muller; Ivan Elmi; Stefano Zampolli; Marta Padilla; Santiago Marco

2008-01-01

396

Sensitivity analysis of a LFE acoustic wave gas sensor with finite element method  

Microsoft Academic Search

In the last decade, there are increasing investigations on lateral field excited (LFE) acoustic wave sensors in biochemical liquid sensing applications due to their high sensitivity and simple fabrication. However, the research on this kind of sensor for gas detection is still awaited. Therefore, we adopted finite element method (FEM) to analyze a LFE acoustic wave gas sensor, and further

Yung-Yu Chen; Chih-Chieh Liu

2009-01-01

397

Measurement Of Quasiparticle Transport In Aluminum Films Using Tungsten Transition-Edge Sensors  

E-print Network

We report new experimental studies to understand the physics of phonon sensors which utilize quasiparticle diffusion in thin aluminum films into tungsten transition-edge-sensors (TESs) operated at 35 mK. We show that basic TES physics and a simple physical model of the overlap region between the W and Al films in our devices enables us to accurately reproduce the experimentally observed pulse shapes from x-rays absorbed in the Al films. We further estimate quasiparticle loss in Al films using a simple diffusion equation approach.

Yen, J J; Young, B A; Cabrera, B; Brink, P L; Cherry, M; Kreikebaum, J M; Moffatt, R; Redl, P; Tomada, A; Tortorici, E C

2014-01-01

398

Nano-gap Effects in Semiconductor Gas Sensors  

NASA Astrophysics Data System (ADS)

The effect of gap size on the gas sensitivity of semiconductor gas sensor was evaluated in the NO2 sensing using WO3 nanosensor, the Cl2 sensing using In2O3 nanosensor and the H2S sensing using SnO2 nanosensor. The nano-gap effect was markedly observed in the NO2-WO3 system and the Cl2-In2O3 system (resistance increase), while the H2S-SnO2 system showed the weak nano-gap effect. This difference resulted from the ratio (Si/Sgb) of sensitivity at semiconductor oxide-electrode interface (Si) to at grain boundary (Sgb). The NO2-WO3 and the Cl2-In2O3 systems showed the large Si/Sgb ratio (32-43), while the small ratio (9.7) was obtained in the H2S-SnO2 system at the gas concentration of 0.5-1 ppm. It was found that the clearer nano-gap effect was obtained for the system having the larger Si/Sgb ratio. In the system having large Si/Sgb ratio, the nano-design of electrode structure like nano-gap electrode was important for high sensitivity gas sensors.

Tamaki, Jun; Miyaji, Akira; Niimi, Jun; Nakataya, Yoshinori; Konishi, Satoshi

399

Room-temperature scanning Hall probe microscope (RT-SHPM) imaging of garnet films using new high-performance InSb sensors  

Microsoft Academic Search

High-performance InSb micro-Hall sensors were fabricated by optical lithography and incorporated in a room-temperature scanning Hall probe microscope for imaging of localized magnetic fluctuations in close proximity to the surfaces of crystalline uniaxial garnet films. The room-temperature noise figure of the InSb sensors was 6-10 mG\\/?Hz, which is an order of magnitude. better than GaAs-AlGaAs two-dimensional electron gas sensors used

A. Oral; A. Kaval; M. Dede; H. Masuda; A. Okamoto; I. Shibasaki; A. Sandhu

2002-01-01

400

Prototype thin-film thermocouple/heat-flux sensor for a ceramic-insulated diesel engine  

NASA Technical Reports Server (NTRS)

A platinum versus platinum-13 percent rhodium thin-film thermocouple/heat-flux sensor was devised and tested in the harsh, high-temperature environment of a ceramic-insulated, low-heat-rejection diesel engine. The sensor probe assembly was developed to provide experimental validation of heat transfer and thermal analysis methodologies applicable to the insulated diesel engine concept. The thin-film thermocouple configuration was chosen to approximate an uninterrupted chamber surface and provide a 1-D heat-flux path through the probe body. The engine test was conducted by Purdue University for Integral Technologies, Inc., under a DOE-funded contract managed by NASA Lewis Research Center. The thin-film sensor performed reliably during 6 to 10 hr of repeated engine runs at indicated mean surface temperatures up to 950 K. However, the sensor suffered partial loss of adhesion in the thin-film thermocouple junction area following maximum cyclic temperature excursions to greater than 1150 K.

Kim, Walter S.; Barrows, Richard F.

1988-01-01

401

Gas Sensors Based on Semiconducting Metal Oxide One-Dimensional Nanostructures  

PubMed Central

This article provides a comprehensive review of recent (2008 and 2009) progress in gas sensors based on semiconducting metal oxide one-dimensional (1D) nanostructures. During last few years, gas sensors based on semiconducting oxide 1D nanostructures have been widely investigated. Additionally, modified or doped oxide nanowires/nanobelts have also been synthesized and used for gas sensor applications. Moreover, novel device structures such as electronic noses and low power consumption self-heated gas sensors have been invented and their gas sensing performance has also been evaluated. Finally, we also point out some challenges for future investigation and practical application. PMID:22303154

Huang, Jin; Wan, Qing

2009-01-01

402

On the dependence of structural and sensing properties of sputtered MoO3 thin films on argon gas flow  

NASA Astrophysics Data System (ADS)

Nitrogen and carbon oxides (CO, NO and NO2), released from combustion facilities and automobiles, are known to be extremely harmful to the human body and also are the main cause of air pollution. Therefore, effective methods to monitor and suppress the carbon and nitrogen oxides have been highly demanded for atmospheric environmental measurements and controls. It is known that molybdenum oxide (MoO3) can be a good semiconductor material for use as a gas sensor in monitoring CO, NO and NO2. In this paper we report the structural characteristics and sensing properties of the sputtered MoO3 thin films as a function of argon gas flow. MoO3 thin films were deposited by DC reactive magnetron sputtering technique on glass substrates at different argon gas flows in the range of 5-20 sccm. X-ray diffraction (XRD) analysis was used for studying crystallographic structure. XRD results showed that all of our films were of polycrystalline structure and of ?-MoO3 stable orthorhombic phase. Results also showed that crystallite size increases while compressive nano-strain in the structure of the films decreases with increasing the argon gas flow. Atomic force microscope and the field emission scanning electron microscope studies showed granular structures for all samples, which increased in size consistent with the XRD results, with argon gas flow, while the surface roughness of the films also increased with argon gas flow. Chemical composition study showed optimum reaction between oxygen and molybdenum atoms for films produced at 15 sccm flow of argon gas. The electrical response of samples was measured in the vacuum and the CO environments in the temperature range of 150-350 K. All samples showed Ohmic behavior and the electrical resistances of the films measured in the CO environment were lower than those measured in vacuum. This study showed that the sensing ability of MoO3 for CO improves with increasing the argon gas flow.

Khojier, K.; Savaloni, H.; Zolghadr, S.

2014-11-01

403

Novel Thin Film Sensor Technology for Turbine Engine Hot Section Components  

NASA Technical Reports Server (NTRS)

Degradation and damage that develops over time in hot section components can lead to catastrophic failure of the turbine section of aircraft engines. A range of thin film sensor technology has been demonstrated enabling on-component measurement of multiple parameters either individually or in sensor arrays including temperature, strain, heat flux, and flow. Conductive ceramics are beginning to be investigated as new materials for use as thin film sensors in the hot section, leveraging expertise in thin films and high temperature materials. The current challenges are to develop new sensor and insulation materials capable of withstanding the extreme hot section environment, and to develop techniques for applying sensors onto complex high temperature structures for aging studies of hot propulsion materials. The technology research and development ongoing at NASA Glenn Research Center for applications to future aircraft, launch vehicles, space vehicles, and ground systems is outlined.

Wrbanek, John D.; Fralick, Gustave C.

2007-01-01

404

Application of PVDF Film Sensor to Detect Early Damage in Wind Turbine Blade Components  

Microsoft Academic Search

Monitoring technique for detection of early damage in the wind turbine blade has been investigated using PVDF film sensor and strain gages. The trailing edge component with shear web was prepared by sectioning the full-scale blade with a box spa. Several PVDF film sensors with dimension of 10x10x0.054 mm3 and strain gages were installed on shear web and skin of

Y.-H. Huh; J. I. Kim; J. H. Lee; S. G. Hong; J. H. Park

2011-01-01

405

Mechanical response of noble gas films to an oscillating substrate  

NASA Astrophysics Data System (ADS)

We carried out quartz-crystal microbalance (QCM) experiments for Xe films adsorbed on an exfoliated single-crystalline graphite substrate (Xe/Gr) and Kr 1ms adsorbed on a synthetic mica substrate (Kr/mica) around LN2 temperature. For Xe/Gr, it was found that the resonance frequency decreases greatly around the first layer completion, while it does not decrease at low coverages. The observed behavior is similar to that of Kr films on a graphite substrate (Kr/Gr). This demonstrates that the layer completion strongly affects the sliding motion of noble gas films on graphite.

Kobayashi, Hajime; Taniguchi, Junko; Suzuki, Masaru; Miura, Kouji; Arakawa, Ichiro

2012-12-01

406

Semiconducting Thin-Film Sensors for Detection of Polluting Gases and Floating Particles  

NASA Astrophysics Data System (ADS)

A micro sensor for polluting gases and organic floating particles has been developed. The sensor is composed of two parts: a sensing element and a micro heater. Both parts are fabricated using thin-film technology, IC fabrication, and a micromachining technique. The sensing film has a double-layered structure; the first layer is a Fe2O3-based thin-film and the second layer is a SnO2-based thin-film. They are deposited by r.f. sputtering on a SiO2/Al2O3/SiO2 diaphragm formed on a Si substrate. A thin-film heater is also fabricated on a similar diaphragm on another Si substrate. The sensing element and the micro heater are placed in parallel at a distance of about 50?m. The sensor is sensitive to polluting gases such as NOX, exhaust gases, cigarette smoke, and organic floating particles such as pollen.

Yokoyama, Tatsuya; Hara, Kazuhiro

407

Characterization of mixed xWO3(1-x)Y2O3 nanoparticle thick film for gas sensing application.  

PubMed

Microstructural, topology, inner morphology, and gas-sensitivity of mixed xWO(3)(1-x)Y(2)O(3) nanoparticles (x = 1, 0.95, 0.9, 0.85, 0.8) thick-film semiconductor gas sensors were studied. The surface topography and inner morphological properties of the mixed powder and sensing film were characterized with X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Also, gas sensitivity properties of the printed films were evaluated in the presence of methane (CH(4)) and butane (C(4)H(10)) at up to 500 °C operating temperature of the sensor. The results show that the doping agent can modify some structural properties and gas sensitivity of the mixed powder. PMID:22399925

Abadi, M H Shahrokh; Hamidon, M N; Shaari, Abdul Halim; Abdullah, Norhafizah; Misron, Norhisam; Wagiran, Rahman

2010-01-01

408

Characterization of Mixed xWO3(1-x)Y2O3 Nanoparticle Thick Film for Gas Sensing Application  

PubMed Central

Microstructural, topology, inner morphology, and gas-sensitivity of mixed xWO3(1-x)Y2O3 nanoparticles (x = 1, 0.95, 0.9, 0.85, 0.8) thick-film semiconductor gas sensors were studied. The surface topography and inner morphological properties of the mixed powder and sensing film were characterized with X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Also, gas sensitivity properties of the printed films were evaluated in the presence of methane (CH4) and butane (C4H10) at up to 500 °C operating temperature of the sensor. The results show that the doping agent can modify some structural properties and gas sensitivity of the mixed powder. PMID:22399925

Shahrokh Abadi, M. H.; Hamidon, M. N.; Shaari, Abdul Halim; Abdullah, Norhafizah; Misron, Norhisam; Wagiran, Rahman

2010-01-01

409

Active Matrix Touch Sensor Perceiving Liquid Crystal Capacitance with Amorphous Silicon Thin Film Transistors  

NASA Astrophysics Data System (ADS)

An active matrix touch sensor is integrated into a liquid crystal display (LCD) panel. The sensor is composed of a liquid crystal capacitor and a sensing circuit with amorphous silicon thin film transistors (a-Si TFTs). The change in sensor capacitance when the sensor is touched is converted into current change by the sensing circuit in the pixel. The proposed touch sensor is pressure-sensitive enough to work at an external push force of 10 gf. The simplified sensing circuit also gives an improved aperture ratio over that in previous work.

Kim, Cheol-Se; Kang, Byung Koo; Jung, Ji Hyun; Lee, Min Jae; Kim, Hun Bae; Oh, Seung Seok; Jang, Su Hyuk; Lee, Hwan Joo; Kastuyoshi, Hiraki; Shin, Jong Keun

2010-03-01

410

Development of Taste Sensor with LB Films for Measurement of High-intensity Sweetener  

NASA Astrophysics Data System (ADS)

Recently, development of taste sensor is furthered for quality control of foods. In this study, we developed taste sensor with stearic acid LB films for measurement of high-intensity sweetener taste. We measured several high-intensity sweeteners with the number of layers of stearic acid LB films as 10 and 20 layers. And we also measured mixed high-intensity sweeteners. The result showed that the stearic acid LB films taste sensor was used to detect glucose and high-intensity sweeteners at a threshold level of taste. Stearic acid LB films sensor detects different response by mixed ratio of high-intensity sweeteners. In addition, we compared difference of sensor responses by three kind of storing conditions (vacuum vessel, KCl solution and the air storing). The result showed that the structure of stearic acid LB films is easily affected by moisture in storage environment. This study indicated that the modification of stearic acid LB film layers and materials makes it possible to develop high sensitivity and selectivity taste sensor for sweeteners.

Asami, Tetsuya; Hasegawa, Yuki; Ando, Ki; Uchida, Hidekazu; Yaji, Tamaki

411

Wireless sensor networks for off-shore oil and gas installations  

E-print Network

­ Underwater development and production of oil and gas needs networked sensors and actuators to monitor the production process, to either prevent or detect oil and gas leakage or to enhance the production flow1 Wireless sensor networks for off-shore oil and gas installations Martin Dalbro, Erik Eikeland

Gjessing, Stein

412

Metallo-porphyrins as gas sensing material for colorimetric gas sensors on planar optical waveguides  

NASA Astrophysics Data System (ADS)

The work presented here focuses on the investigations of metallo-porphyrins and their gasochromic behavior. Gasochromic materials change their color while they are exposed to a certain gas. So they offer the possibility to develop very selective chemical gas sensors. In the focus of this work is the metallo-porphyrin 5, 10, 15, 20- tetraphenylporphyrin-zinc (ZnTPP). When embedded into a polymeric matrix (PVC) the color change to the toxic gas NO2 can be detected. During exposure to NO2 the dye changes its color from bright purple to yellow. To develop a standalone gas sensor, the ZnTPP/PVC matrix is deposited onto a planar optical waveguide. The color change of the porphyrin dye, due to the gas exposure, can be detected in the evanescent field of the optical waveguide. Therefore the light of a high power LED is coupled into the waveguide. The color change of the porphyrin is detectable with photodiodes as variations of the decoupled light intensity. The sensor shows no cross-sensitivities to other gases like CO2, NH3, EtOH, CO or water vapor. NO2 is detectable with a limit of 1 ppm.

Peter, Carolin; Schmitt, Katrin; Schiel, Martin; Wöllenstein, Jürgen

2011-06-01

413

Field testing the Raman gas composition sensor for gas turbine operation  

SciTech Connect

A gas composition sensor based on Raman spectroscopy using reflective metal lined capillary waveguides is tested under field conditions for feed-forward applications in gas turbine control. The capillary waveguide enables effective use of low powered lasers and rapid composition determination, for computation of required parameters to pre-adjust burner control based on incoming fuel. Tests on high pressure fuel streams show sub-second time response and better than one percent accuracy on natural gas fuel mixtures. Fuel composition and Wobbe constant values are provided at one second intervals or faster. The sensor, designed and constructed at NETL, is packaged for Class I Division 2 operations typical of gas turbine environments, and samples gas at up to 800 psig. Simultaneous determination of the hydrocarbons methane, ethane, and propane plus CO, CO2, H2O, H2, N2, and O2 are realized. The capillary waveguide permits use of miniature spectrometers and laser power of less than 100 mW. The capillary dimensions of 1 m length and 300 μm ID also enable a full sample exchange in 0.4 s or less at 5 psig pressure differential, which allows a fast response to changes in sample composition. Sensor operation under field operation conditions will be reported.

Buric, M.; Chorpening, B.; Mullem, J.; Ranalli, J.; Woodruff, S.

2012-01-01

414

IN SITU WAFER-LEVEL POLARIZATION OF ELECTRET FILMS IN MEMS ACOUSTIC SENSOR ARRAYS  

E-print Network

IN SITU WAFER-LEVEL POLARIZATION OF ELECTRET FILMS IN MEMS ACOUSTIC SENSOR ARRAYS M. Kranz 1 , M to a single-chip array of acoustic sensors designed to capture and analyze waveforms from impacts. KEYWORDS, significant discharge can occur if exposed to temperatures near the glass transition of the polymer, thereby

415

Characterization of gas-phase adsorption on metal oxide thin films using a magnetoelastic resonance microbalance.  

PubMed

In this study, a magnetoelastic resonance microbalance (MERM) was used to directly measure the gas-phase adsorption behavior of water vapor, isopropyl alcohol, and acetone on a sol-gel-derived titanium dioxide sensor coating. The nature of the MERM platform enables chemical measurements in situations in which wires or physical connections are undesired (or not possible) or in which sensor cost is a major issue. The underlying MERM technique (with an uncoated sensor) showed excellent day-to-day stability, a linear calibration over a 1 kHz change in frequency (or a 1.5-mg change in mass), and the ability to detect a mass change of 15 microg without any efforts at sensitivity optimization. The titanium dioxide coated sensor yielded excellent response to each of the analytes; however, the response did not follow a simple linear calibration function. A more complex calibration model or utilization of the coated sensor in a limited concentration range would be required for quantitative analysis. The process of applying the metal oxide coatings onto the magnetic substrate altered the structure of the thin film layer, resulting in a relatively loose packing of the porous primary titanium dioxide particles to create an open overall honeycomb structure, thereby affecting the adsorption behavior at high relative concentration. PMID:14616005

Zorn, Michael E; Rahne, Kari A; Tejedor-Tejedor, M Isabel; Anderson, Marc A; Grimes, Craig A

2003-11-15

416

A micro oxygen sensor based on a nano sol-gel TiO2 thin film.  

PubMed

An oxygen gas microsensor based on nanostructured sol-gel TiO2 thin films with a buried Pd layer was developed on a silicon substrate. The nanostructured titania thin films for O2 sensors were prepared by the sol-gel process and became anatase after heat treatment. A sandwich TiO2 square board with an area of 350 ?m × 350 ?m was defined by both wet etching and dry etching processes and the wet one was applied in the final process due to its advantages of easy control for the final structure. A pair of 150 nm Pt micro interdigitated electrodes with 50 nm Ti buffer layer was fabricated on the board by a lift-off process. The sensor chip was tested in a furnace with changing the O2 concentration from 1.0% to 20% by monitoring its electrical resistance. Results showed that after several testing cycles the sensor's output becomes stable, and its sensitivity is 0.054 with deviation 2.65 × 10(-4) and hysteresis is 8.5%. Due to its simple fabrication process, the sensor has potential for application in environmental monitoring, where lower power consumption and small size are required. PMID:25192312

Wang, Hairong; Chen, Lei; Wang, Jiaxin; Sun, Quantao; Zhao, Yulong

2014-01-01

417

A Micro Oxygen Sensor Based on a Nano Sol-Gel TiO2 Thin Film  

PubMed Central

An oxygen gas microsensor based on nanostructured sol-gel TiO2 thin films with a buried Pd layer was developed on a silicon substrate. The nanostructured titania thin films for O2 sensors were prepared by the sol-gel process and became anatase after heat treatment. A sandwich TiO2 square board with an area of 350 ?m × 350 ?m was defined by both wet etching and dry etching processes and the wet one was applied in the final process due to its advantages of easy control for the final structure. A pair of 150 nm Pt micro interdigitated electrodes with 50 nm Ti buffer layer was fabricated on the board by a lift-off process. The sensor chip was tested in a furnace with changing the O2 concentration from 1.0% to 20% by monitoring its electrical resistance. Results showed that after several testing cycles the sensor's output becomes stable, and its sensitivity is 0.054 with deviation 2.65 × 10?4 and hysteresis is 8.5%. Due to its simple fabrication process, the sensor has potential for application in environmental monitoring, where lower power consumption and small size are required. PMID:25192312

Wang, Hairong; Chen, Lei; Wang, Jiaxin; Sun, Quantao; Zhao, Yulong

2014-01-01

418

Design and fabrication of a CMOS-compatible MHP gas sensor  

SciTech Connect

A novel micro-hotplate (MHP) gas sensor is designed and fabricated with a standard CMOS technology followed by post-CMOS processes. The tungsten plugging between the first and the second metal layer in the CMOS processes is designed as zigzag resistor heaters embedded in the membrane. In the post-CMOS processes, the membrane is released by front-side bulk silicon etching, and excellent adiabatic performance of the sensor is obtained. Pt/Ti electrode films are prepared on the MHP before the coating of the SnO{sub 2} film, which are promising to present better contact stability compared with Al electrodes. Measurements show that at room temperature in atmosphere, the device has a low power consumption of ?19 mW and a rapid thermal response of 8 ms for heating up to 300 °C. The tungsten heater exhibits good high temperature stability with a slight fluctuation (<0.3%) in the resistance at an operation temperature of 300 °C under constant heating mode for 336 h, and a satisfactory temperature coefficient of resistance of about 1.9‰/°C.

Li, Ying; Yu, Jun, E-mail: junyu@dlut.edu.cn; Wu, Hao; Tang, Zhenan [College of Electronic Science and Technology, Dalian University of Technology, Dalian 116024 (China)] [College of Electronic Science and Technology, Dalian University of Technology, Dalian 116024 (China)

2014-03-15

419

A composite thin film optical sensor for dissolved oxygen in contaminated aqueous environments  

Microsoft Academic Search

A robust optical composite thin film dissolved oxygen sensor was fabricated by ionically trapping the dye ruthenium(II) tris(4,7-diphenyl-1,10-phenanthroline) dichloride in a blended fluoropolymer matrix consisting of Nafion® and Aflas®. Strong phosphorescence, which was strongly quenched by dissolved oxygen (DO), was observed when the sensor was immersed in water. The sensor was robust, optically transparent, with good mechanical properties. Fast response,

R. N. Gillanders; M. C. Tedford; P. J. Crilly; R. T. Bailey

2005-01-01

420

Wireless Biomedical Signal Monitoring Device on Wheelchair using Noncontact Electromechanical Film Sensor  

Microsoft Academic Search

The present study purposed to measure the BCG (Ballistocardiogram) of subjects on a wheelchair using a noncontact electro-mechanical film sensor (EMFi sensor) and detect the respiratory rate from BCG in real-time while the subjects are moving. In order to measure wirelessly the BCG of subjects moving on a wheelchair, we made a seat-type noncontact EMFi sensor and developed a transmitter

Jong-Myoung Kim; Joo-Hyun Hong; Myeong-Chan Cho; Eun-Jong Cha; Tae-Soo Lee

2007-01-01

421

Measurement of radiation induced transients in hybrid microcircuits by magnetic thin film sensor\\/recorders  

Microsoft Academic Search

Magnetic thin film transient current sensor\\/recorders were modified to make two types of nuclear test measurements, transient currents in hybrid microcircuits, and internal electromagnetic pulse (IEMP) fields. The measurements were made possible by the invention of split-domain sensor\\/recorders which can measure bilateral currents and can be reset and readout on location. The sensor\\/recorders were used in two underground nuclear tests

E. J. Hsieh; K. E. Vindelov; T. G. Brown; D. E. Miller

1976-01-01

422

Optical Breath Gas Sensor for Extravehicular Activity Application  

NASA Technical Reports Server (NTRS)

The function of the infrared gas transducer used during extravehicular activity (EVA) in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation Portable Life Support System (PLSS) requires next generation CO2 sensing technology with performance beyond that presently in use on the Shuttle/International Space Station extravehicular mobility unit (EMU). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode (LD) spectrometer based on wavelength modulation spectroscopy (WMS) is being developed for this purpose by Vista Photonics, Inc. Two prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The sensors incorporate a laser diode based CO2 channel that also includes an incidental water vapor (humidity) measurement and a separate oxygen (O2) channel using a vertical cavity surface emitting laser (VCSEL). Both prototypes are controlled digitally with a field-programmable gate array (FPGA)/microcontroller architecture. Based on the results of the initial instrument development, further prototype development and testing of instruments leveraging the lessons learned were desired. The present development extends and upgrades the earlier hardware to the Advanced PLSS 2.0 test article being constructed and tested at JSC. Various improvements to the electronics and gas sampling are being advanced by this project. The combination of low power electronics with the performance of a long wavelength laser spectrometer enables multi-gas sensors with significantly increased performance over that presently offered in the EMU. .

Wood, William R.; Casias, Miguel E.; Vakhtin, Andrei B.; Pilgrim, Jeffrey S> ; Chullen, Cinda; Falconi, Eric A.

2012-01-01

423

Flashback Detection Sensor for Hydrogen Augmented Natural Gas Combustion  

SciTech Connect

The use of hydrogen augmented fuel is being investigated by various researchers as a method to extend the lean operating limit, and potentially reduce thermal NOx formation in natural gas fired lean premixed (LPM) combustion systems. The resulting increase in flame speed during hydrogen augmentation, however, increases the propensity for flashback in LPM systems. Real-time in-situ monitoring of flashback is important for the development of control strategies for use of hydrogen augmented fuel in state-of-the-art combustion systems, and for the development of advanced hydrogen combustion systems. The National Energy Technology Laboratory (NETL) and Woodward Industrial Controls are developing a combustion control and diagnostics sensor (CCADS), which has already been demonstrated as a useful sensor for in-situ monitoring of natural gas combustion, including detection of important combustion events such as flashback and lean blowoff. Since CCADS is a flame ionization sensor technique, the low ion concentration produced in pure hydrogen combustion raises concerns of whether CCADS can be used to monitor flashback in hydrogen augmented combustion. This paper discusses CCADS tests conducted at 0.2-0.6 MPa (2-6 atm), demonstrating flashback detection with fuel compositions up to 80% hydrogen (by volume) mixed with natural gas. NETL’s Simulation Validation (SimVal) combustor offers full optical access to pressurized combustion during these tests. The CCADS data and high-speed video show the reaction zone moves upstream into the nozzle as the hydrogen fuel concentration increases, as is expected with the increased flame speed of the mixture. The CCADS data and video also demonstrate the opportunity for using CCADS to provide the necessary in-situ monitor to control flashback and lean blowoff in hydrogen augmented combustion applications.

Thornton, J.D.; Chorpening, B.T.; Sidwell, T.; Strakey, P.A.; Huckaby, E.D.; Benson, K.J. (Woodward)

2007-05-01

424

Thin polymer films as active components of fiber optic chemical sensors  

Microsoft Academic Search

Thin polymer films provide a convenient matrix in which to support a variety of indicator molecules that are distinguished by their ability to modulate light signals when exposed to specific analytes of interest. Using this general idea, sensors have been developed from both planar waveguides and optical fibers in conjunction with thin polymer films for a variety of process monitoring

Henrik Pedersen; Tony Alex; H. Ling Chu; Wook-Jin Chung; George H. Sigel

1993-01-01

425

Gold promoted Li–Fe 2O 3 thin films for humidity sensors  

Microsoft Academic Search

A study of iron oxide thin films doped with Li and Au for humidity sensing applications is reported. The characteristics of sensitivity, linearity and stability of humidity sensors based on these films were investigated and correlated to the structural and textural properties of the sensing layer. Such properties are influenced by the nature of the dopant and the thermal treatment.

G. Neri; A. Bonavita; C. Milone; A. Pistone; S. Galvagno

2003-01-01

426

Use of plasma polymerized highly hydrophobic hexamethyldissilazane (HMDS) films for sensor development  

E-print Network

spectroscopy, optical and Raman microscopy. Deposition on piezoelectric quartz crystal (PQC) showed adsorption character to the film surface [6,7]. In this work, thin films were obtained by plasma poly- merization enhanced chemical vapor deposition (PECVD) in a low frequency Sensors and Actuators B 91 (2003) 362

427

Mesoporous Thin Films of "Molecular Squares" as Sensors for Volatile Organic Compounds  

E-print Network

-metal-based "molecular squares"1-8 and related ligand-bridged met- allacycles (rectangles,9 triangles,10 hexagons,11 etcMesoporous Thin Films of "Molecular Squares" as Sensors for Volatile Organic Compounds Melinda H films of rhenium-based "molecular squares", [Re(CO)3Cl(L)]4 (L ) pyrazine, 4,4- bipyridine), have been

428

Thin film magnetostrictive sensor with on-chip readout and attoFarad capacitance resolution  

Microsoft Academic Search

We report the first successful integration of magnetostrictive Metglas (Fe 78Si 9B 13) thin film sensor with a readout circuit using standard integrated circuit (IC) process and surface micromachining. The Metglas thin film is on a nitride cantilever beam. Its magnetic domains are subject to rotation in a magnetic field. This induces a strain and hence, beam deflection which is

Y. Lu; A. Nathan; T. Manku; Y. Ning

1996-01-01

429

Gas sensor technology at Sandia National Laboratories: Catalytic gate, Surface Acoustic Wave and Fiber Optic Devices  

SciTech Connect

Sandia`s gas sensor program encompasses three separate electronic platforms: Acoustic Wave Devices, Fiber Optic Sensors and sensors based on silicon microelectronic devices. A review of most of these activities was presented recently in a article in Science under the title ``Chemical Microsensors.`` The focus of the program has been on understanding and developing the chemica