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1

New fabrication of zinc oxide nanostructure thin film gas sensors  

NASA Astrophysics Data System (ADS)

The copper doped zinc oxide thin films have been prepared by sol-gel spin coating method. The structural and morphology properties of the Cu doped films were characterized by X-ray diffraction and atomic force microscope. XRD studies confirm the chemical structure of the ZnO films. The optical spectra method were used to determined optical constants and dispersion energy parameters of Cu doped Zno thin films. The optical band gap of undoped ZnO was found to be 3.16 eV. The Eg values of the films were changed with Cu doping. The refractive index dispersion of Cu doped ZnO films obeys the single oscillator model. The dispersion energy and oscillator energy values of the ZnO films were changed with Cu doping. The Cu doped ZnO nanofiber-based NH3 gas sensors were fabricated. The sensor response of the sensors was from 464.98 to 484.61 when the concentration of NH3 is changed 6600-13,300 ppm. The obtained results indicate that the response of the ZnO film based ammonia gas sensors can be controlled by copper content.

Hendi, A. A.; Alorainy, R. H.

2014-02-01

2

Various characteristic of Carbon nanotubes film methane Gas sensor  

Microsoft Academic Search

Various sensing characteristic of carbon nanotube synthesized by low press chemical vapor deposit (LPCVD) method have been studied. The composite sensing film of silicon dioxide and multi-wall nanotubes (SiO 2-MWNTs) is sensitive to methane. The various characteristic such as sensitivity, repeatability, reliability and cross-sensitivity of SiO2-MWNTs composite film gas sensor have been studied. Having been tested in methane 3 times,

Xin Li; Junhua Liu; Changchun Zhu

2006-01-01

3

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 600C. 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

4

A study of tin oxide thin film gas sensors with high oxygen vacancies  

Microsoft Academic Search

In this paper, gas sensors employing nanoscale tin oxide films of high oxygen vacancies were successfully made and tested in order to determine which factors affected the gas sensitivity of them. Firstly electrothermal simulations were carried out to predict the steady-state temperature distributions of the tin oxide thin film and the overall gas sensor using ANSYS. Then the composition of

Chen Lin; Dacheng Zhang; Xiaodi Liu

2012-01-01

5

Thermo-Resistive Platinum Thin Film Hydrogen Gas Sensor Fabricated by MEMS Techniques  

NASA Astrophysics Data System (ADS)

Thermo-resistive platinum(Pt) thin film sensor was produced using Micro Electro Mechanical Systems (MEMS) fabrication techniques. The sensor design incorporated resistor elements that would facilitate the temperature-resistance characteristics and mechanisms of Pt based thin film thermo-resistors. The sensor was fabricated with lift-off process that allowed the dual sensing surface area. Furthermore, the dual sensing surfaces ensured faster response to hydrogen gas. To increase the catalytic reaction comparing with at the room temperature, the sensor was heated to a specified temperature by applying the current to a Pt thin film. The catalytic reaction took place when the heated sensor came into the contact with hydrogen. Additionally, the differential Pt thin film hydrogen gas sensor was also developed. This gas sensor was able to compensate the changes in the external environment such as temperature, moisture, etc. The fabricated hydrogen sensor detected the concentration of hydrogen gas in air from 2% to 9%.

Yamazaki, Daisuke; Zhang, Lin; Pawlat, Joanna; Ueda, Toshitsugu

6

Thin-film Li-doped NiO for thermoelectric hydrogen gas sensor  

Microsoft Academic Search

A hydrogen gas sensor using thermoelectric (TE) Li-doped NiO thin film with platinum catalyst film on the half of its surface was fabricated and this thin-film sensor has strong adhesion on the substrate. When this sensor is exposed to air mixed with the hydrogen gas, catalytic reaction heats up the platinum-coated surface, and then TE voltage builds up along the

Masahiko Matsumiya; Fabin Qiu; Woosuck Shin; Noriya Izu; Norimitsu Murayama; Shuzo Kanzaki

2002-01-01

7

Gas sensitivity studies by optical spectroscopy below the absorption edge in tin oxide thin film sensors  

Microsoft Academic Search

Optical transmission spectra are investigated experimentally below the fundamental absorption edge in tin oxide thin film-based gas sensors. The spectra are studied under different conditions for gas chemisorption when the resistance response to gas is modified by heating of the sensors in various atmospheres or adding of impurity metals into tin oxide. Optical bandgap, refractive coefficient and optical absorption index

A. Galdikas; A Mironas; D Senulien?; A etkus

1998-01-01

8

Optical gas sensor based on MgTPP thin film for the detection of alcohol vapors  

Microsoft Academic Search

Electronic nose devices are of increasing interest for the quality control of beverage and food processing. Optical gas sensors that require low electrical power are in great need for such devices. Magnesium 5, 10, 15, 20-tetraphenylporphyrin thin film sensors have been fabricated by spin coating onto glass substrates for detecting specific alcoholic volatile organic compounds (VOCs). Responses of the films

Johannes Mensing; Sumana Kladsomboon; Teerakiat Kerdcharoen

2008-01-01

9

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

10

Peculiarities of surface doping with Cu in SnO 2 thin film gas sensors  

Microsoft Academic Search

It is demonstrated that a small amount of Cu impurity (less than 1 at.%) significantly modifies the properties of tin oxide thin films used for the gas sensors. Different amount of Cu (between 0.5 and 7 at.%) was sputtered on the top of the films. The structure, surface chemical composition, optical and electrical properties are studied for these films. It

A. Galdikas; V. Jasutis; S. Ka?iulis; G. Mattogno; A. Mironas; V. Olevano; D. Senulien?; A. etkus

1997-01-01

11

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

Microsoft Academic Search

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

A Galdikas; A Mironas; A etkus; W Gpel; K.-D Schierbaum

1999-01-01

12

Preparation of tin oxide and insulating oxide thin films for multilayered gas sensors  

NASA Astrophysics Data System (ADS)

Crack-free SnO2 and SiO2 films with the controlled thickness up to 1 micrometers have been prepared by the sol-gel spin coating method. Preparation conditions and microstructure of the films are described. Gas sensing elements consisting of single SnO2 thin film and multi-layered SiO2/SnO2 thin films have been prepared using this method. Comparison of sensing properties between single SnO2 thin film and multi-layered thin film sensing elements shows potential advantage for developing selective gas sensors.

Feng, Chang D.; Shimizu, Yasuhiro; Egashira, Makoto

1991-11-01

13

The effects of two thick film deposition methods on tin dioxide gas sensor performance.  

PubMed

This work demonstrates the variability in performance between SnO(2) thick film gas sensors prepared using two types of film deposition methods. SnO(2) 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

14

Thermoelectric Thick-Film Hydrogen Gas Sensor Operating at Room Temperature  

Microsoft Academic Search

A sensor of thick film NiO doped with alkali ions was fabricated and coated with Pt as the catalyst on half of its surface. When this sensor was exposed to air mixed with hydrogen gas, the catalytic reaction heated up the Pt-coated surface, and then thermoelectric voltage appeared across the hot and cold region of the oxide film. At 22C,

Woosuck Shin; Kiyohisa Imai; Noriya Izu; Norimitsu Murayama

2001-01-01

15

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

PubMed Central

Zeolites are promising materials in the field of gas sensors. In this technology-oriented paper, a planar setup for potentiometric hydrocarbon and hydrogen gas sensors using zeolites as ionic sodium conductors is presented, in which the Pt-loaded Na-ZSM-5 zeolite is applied using a thick-film technique between two interdigitated gold electrodes and one of them is selectively covered for the first time by an electroplated chromium oxide film. The influence of the sensor temperature, the type of hydrocarbons, the zeolite film thickness, and the chromium oxide film thickness is investigated. The influence of the zeolite on the sensor response is briefly discussed in the light of studies dealing with zeolites as selectivity-enhancing cover layers. PMID:22164042

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

2011-01-01

16

Gas detection with SnO 2 sensors modified by zeolite films  

Microsoft Academic Search

Zeolite films have been grown on top of SnO2 sensors to modify their response to gas phase molecules with the aim of improving their selectivity. To this end SnO2 sensors were first prepared using conventional procedures, and then zeolite layers (silicalite and zeolite A) were grown on the outer SnO2 surface, using different synthesis procedures. The zeolite-modified sensors were tested

Montserrat Vilaseca; Joaquin Coronas; Albert Cirera; Albert Cornet; Joan Ramon Morante; Jesus Santamaria

2007-01-01

17

Stability and oxidation of the sandwich type gas sensors based on thin metal films  

Microsoft Academic Search

The stability of the properties is investigated in the new family of the solid-state gas sensors based on various thin metal films (Pt, Au, Ni, Mo) with the modifying top layer of tin oxide. The resistance response to exposure to gas is demonstrated being stable within certain interval of temperatures. The limits of the interval depend on the metal selected

A. Galdikas; S. Ka?iulis; G. Mattogno; A. Mironas; A. etkus

1998-01-01

18

Development of a novel gas sensor based on oxide thick films  

Microsoft Academic Search

Zinc and iron oxide thick film gas sensors were fabricated using screen-printing technology on glass substrates that had silver interdigitated electrodes. The sensor was used to detect methanol, ethanol and propanol with a concentration range of 08000ppm. Using the formula to calculate a change in resistance, ?R=Rgas?Rair, resistance was seen to increase linearly alongside increasing concentrations of the gas vapours.

K. Arshak; I. Gaidan

2005-01-01

19

Classification of chemical warfare agents using thick film gas sensor array  

Microsoft Academic Search

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

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

2005-01-01

20

Processing-microstructure-property relationships of tin oxide thin films for gas sensor applications  

NASA Astrophysics Data System (ADS)

Tin dioxide (SnO2) with rutile type structure is a wide band n-type semiconductor which exhibits unique electronic and optical properties. In application of this material as gas sensors, a film form of SnO2 provides high surface area to volume ratio and leads to high sensitivity and fast responses. It has been found that the substrate material, the deposition conditions and the annealing procedure may directly influence the microstructure of thin films, hence control gas sensing properties. This thesis describes a concerted effort to study the microstructure-property relationship in SnO 2 thin film sensors. Our studies help to elucidate the effects of microstructure on sensor performance and provide some fundamental understanding of sensor design principals. Thin films with different microstructures were obtained by using two deposition techniques, namely pulsed laser deposition (PLD) and electron-beam evaporation, and a variety of substrates, such as Al2O3(1012), Al2O3(1120) and Al2O3(0001). The obtained SnO2 thin films include single crystalline films, compact epitaxial films with different grain boundary density, and porous films with rough surface. Property measurements reveal that single crystal has low gas sensitivity and the performance of compact films depends on the grain boundary density. On the other hand, porous films exhibit high sensitivity. Based on the experimental results, a model is proposed to interpret the observed phenomena in terms of depletion and grain boundary. We also investigated the effects of film thickness and additives, both bulk and surface, on gas sensitivity. Among the three films examined with thickness of 20nm, 60nm and 100nm, the thinnest film showed better sensitivity than the thicker ones. Dopants influence the sensitivity through the modification of depletion region. Trivalent additives (acceptor type) result in increased depletion layer thickness, hence improve sensor performance. On the contrary, films doped by pentavalent additives (donor type) only have very low gas sensitivity due to the thin depletion layer in the films. We believe that the volume ratio of the depletion region over the total volume is a key factor in determining sensitivity. Addition of surface Pt, even with a thickness of 1nm, is an effective way for improving gas sensitivity.

Fu, Li

21

Room temperature SnO2 thin film gas sensor fabricated on Si nanospikes.  

PubMed

The SnO2 thin film CO gas sensors have been fabricated on silicon nanostructured surface made using a femtosecond pulsed laser irradiation. The measurement shows a significant response to the CO gas at room temperature. While a SnO2 sensor fabricated on a flat surface shows no response when CO gas exists at room temperature. The high area/volume ratio and sharp structures of the nanospikes enhance the sensitivity of SnO2 at room temperature. PMID:19928155

Huo, H B; Wang, C; Yan, F D; Ren, H Z; Shen, M Y

2009-08-01

22

Interaction between thin-film tin oxide gas sensor and five organic vapors  

Microsoft Academic Search

A thin-film tin oxide gas sensor was tested in a flow system for the sensitivity to each vapor (10, 102, 103 ppm in air) of methanol, ethanol, isopropanol, acetone and acetic acid. With a change in operating temperature, the sensitivity to each vapor went through a maximum around 450C. When compared at the same vapor concentration, the sensitivity was in

H. Gong; Y. J. Wang; S. C. Teo; L. Huang

1999-01-01

23

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

PubMed

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

Chaisitsak, Sutichai

2011-01-01

24

Nanocrystalline SnO2:F Thin Films for Liquid Petroleum Gas Sensors  

PubMed Central

This paper reports the improvement in the sensing performance of nanocrystalline SnO2-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO2 films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO2 with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO2:F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO2 was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO2:F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection. PMID:22164007

Chaisitsak, Sutichai

2011-01-01

25

Grain Size Effects in Sensor Response of Nanostructured SnO2- and In2O3Based Conductometric Thin Film Gas Sensor  

Microsoft Academic Search

Based on the experimental results, obtained by studying both structural and gas-sensing properties of the SnO2 and In2O3 films deposited by the spray pyrolysis method, we analyzed the influence of crystallite size on the parameters of the SnO2- and In2O3-based thin film solid-state gas sensors. For comparison, the behavior of ceramic-type gas sensors was considered as well. In particular, we

G. Korotcenkov; S.-D. Han; B. K. Cho; V. Brinzari

2009-01-01

26

Effect of growth catalysts on gas sensitivity in carbon nanotube film based chemiresistive sensors  

NASA Astrophysics Data System (ADS)

Multiwalled carbon nanotube (MWCNT) films have been deposited by using plasma enhanced chemical vapor deposition (PECVD) system onto Cr-Au patterned alumina substrates for NO2 and NH3 gas sensing applications, at operating temperature of 200C. Nanoclusters of different MWCNT-growth catalysts (Fe and Co) have been predeposited onto substrates to promote the growth of the carbon nanotube films with different structural properties. It is demonstrated that the gas sensitivity of the MWCNT films depends on catalyst used for their growth with highest gas sensitivity achieved for Co-grown MWCNT films. The chemiresistor gas response is attributed to the p-type conductivity in semiconducting MWCNTs and the electrical charge transfer is found to be the major sensing mechanism. The results obtained demonstrate that the MWCNT-based sensors exhibit high gas sensitivity, fast response and reversibility, good repeatability and reproducibility, and sub-ppm range detection limit with the gas sensing properties of the MWCNT films tailored by catalyst employed in the PECVD growth process.

Penza, M.; Cassano, G.; Rossi, R.; Rizzo, A.; Signore, M. A.; Alvisi, M.; Lisi, N.; Serra, E.; Giorgi, R.

2007-03-01

27

TiO 2 anatase thin films as gas sensors  

Microsoft Academic Search

The anatase modification of TiO2 shows properties quite different from those of the extensively studied and used rutile phase. We have investigated the chemi-resistive behavior of anatase TiO2 thin films exposed to oxidizing and reducing gases (O2, H2 and ethanol) in the temperature range between 300 and 400 C. The undoped anatase films demonstrate significant and rapid response to ethanol

H. Tang; K. Prasad; R. Sanjins; F. Lvy

1995-01-01

28

Influence of metallic impurities on response kinetics in metal oxide thin film gas sensors  

Microsoft Academic Search

The kinetics of the resistance response to a steep change in gas composition is experimentally and theoretically investigated in SnO2-based thin film sensors modified by different catalytic metals. H2 and CO gases were used in the tests. Based on the phenomenological model, the transients of the resistance response are described by a combination of the characteristics of both the layer

A. etkus; C. Baratto; E. Comini; G. Faglia; A. Galdikas; . Kancleris; G. Sberveglieri

2004-01-01

29

Processing-microstructure-property relationships of tin oxide thin films for gas sensor applications  

Microsoft Academic Search

Tin dioxide (SnO2) with rutile type structure is a wide band n-type semiconductor which exhibits unique electronic and optical properties. In application of this material as gas sensors, a film form of SnO2 provides high surface area to volume ratio and leads to high sensitivity and fast responses. It has been found that the substrate material, the deposition conditions and

Li Fu

2000-01-01

30

Gas Sensing Properties of Metal Doped WO3 Thin Film Sensors Prepared by Pulsed Laser Deposition and DC Sputtering Process  

Microsoft Academic Search

Tungsten trioxide (WO3) thin films gas sensors were prepared by the KrF excimer pulsed laser deposition (PLD) method. The films were prepared on the quartz glass, silicon and also on the Al2O3 sensor substrates with platinum interdigitated electrodes. The effect of doping of the platinum (Pt), palladium (Pd) or gold (Au) on the WO3 thin film was also investigated. These

Tsuyoshi Ueda; Tomoaki Ikegami; Kenji Ebihara

2006-01-01

31

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

Microsoft Academic Search

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

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

2010-01-01

32

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

2015-01-01

33

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

34

Structural approach to improve the response characteristics of copper phthalocyanine thin film-based NO{sub 2} gas sensor  

SciTech Connect

In order to realize a high-sensitivity, low temperature operable NO{sub 2} gas sensor, thin films of {alpha}-form copper phthalocyanine ({alpha}-CuPc) have been deposited by vacuum sublimation. In this study, the authors have attempted to improve the gas-sensing characteristics through a modification of the film microstructure. Firstly, the gas sensitivity is remarkably increased by an insertion of higher-sensitive layer (vanadyl Pc film) between the {alpha}-CuPc film and the glass substrate in the low gas concentration range. Secondly, a reversibility in cycles of gas doping and dedoping is improved by film deposition on hydrofluoric acid-treated substrate. It is found from atomic force microscope analyses that this phenomenon may be closely related to a modification of the film microstructure.

Nagasawa, Tadashi; Murakami, Kenji; Watanabe, Kenzo

1998-07-01

35

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

36

Modified zinc oxide thick film resistors as NH 3 gas sensor  

Microsoft Academic Search

Screen printed thick films of pure and RuO2-doped zinc oxide were prepared. Pure zinc oxide films were also surface modified with ruthenium chloride. Gas sensing properties of the pure, doped and surface modified films were studied. The films were observed to be most sensitive to NH3 gas. The results are discussed and interpreted.

M. S. Wagh; G. H. Jain; D. R. Patil; S. A. Patil; L. A. Patil

2006-01-01

37

Microfabricated gas sensor systems with sensitive nanocrystalline metal-oxide films  

Microsoft Academic Search

This article gives an overview on recent developments in metal-oxide-based gas sensor systems, in particular on nanocrystalline\\u000a oxide materials deposited on modern, state-of-the-art sensor platforms fabricated in microtechnology. First, metal-oxide-based\\u000a gas sensors are introduced, and the underlying principles and fundamentals of the gas sensing process are laid out. In the\\u000a second part, the different deposition methods, such as evaporation, sputtering,

M. Graf; A. Gurlo; N. Brsan; U. Weimar; A. Hierlemann

2006-01-01

38

Properties of palladium doped tin oxide thin films for gas sensors grown by PLD method combined with sputtering process  

Microsoft Academic Search

The gas sensors based on tin dioxide (SnO2) thin films and doped with different amount of palladium (Pd) were synthesized by a new developed preparation system using the pulsed Nd:YAG (532 nm) laser deposition method combined with d.c. sputtering. The Pd-doped SnO2 (SnO2Pd) thin films have been grown on Si (100) and alumina (Al2O3) substrates using SnO2 targets. The composition

Yoshiaki Suda; Hiroharu Kawasaki; Jun Namba; Keitarou Iwatsuji; Kazuya Doi; Kenji Wada

2003-01-01

39

Surface plasmon resonance-based fiber optic hydrogen sulphide gas sensor utilizing Cu-ZnO thin films.  

PubMed

We report an experimental study on a surface plasmon resonance (SPR)-based fiber optic hydrogen sulphide gas sensor with a thin metal oxide (zinc oxide (ZnO)) layer as the additional layer. This zinc oxide layer is grown over the copper layer to support surface plasmons at the metal-dielectric interface at room temperature. The wavelength interrogation mode of operation has been used to characterize the sensor. The thin film of zinc oxide over the copper film was deposited on the unclad portion of the fiber by the thermal evaporation technique. Experiments were performed for the detection of concentrations of hydrogen sulphide gas varying from 0 to 100 ppm around the probe. The unpolarized light from a polychromatic source is launched from one end of the fiber and the corresponding SPR spectrum is recorded at the other end. The recorded SPR spectrum shows a shift in the resonance wavelength on a change in the hydrogen sulphide gas concentration, which is considered as a detectable signal for the characterization of the sensor. Further, the optimization of the performance of the sensor was achieved by varying the thickness of the zinc oxide film. The sensor possesses a very fast response time and high sensitivity. Since the sensor utilizes optical fibers it has additional advantages of remote sensing, online monitoring, light weight and low cost. PMID:23764905

Tabassum, Rana; Mishra, Satyendra K; Gupta, Banshi D

2013-07-28

40

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

41

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 2-10ppm 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

42

SnO2/Pt thin film laser ablated gas sensor array.  

PubMed

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

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

2011-01-01

43

Study of nano Fe2O3 MOS thick films as ethanol gas sensor  

Microsoft Academic Search

Thick films of AR Grade nano Fe2O3 material with n type semiconducting properties were prepared and tested for their gas sensing performances. Thick films of the materials were prepared by screen printing technique. The gas sensing performance was studied using static gas sensing system. The material was tested for various gases such as CO, CO2, NH3, Cl2, H2, LPG, ethanol

G. H. Jain; N K Pawar

2011-01-01

44

A highly sensitive and selective hydrogen gas sensor from thick oriented films of MoS2  

NASA Astrophysics Data System (ADS)

A new process is developed to fabricate a highly sensitive and selective hydrogen sensor by depositing a partially crystalline and highly oriented film of MoS2 from its single layer suspension on an alumina substrate. When these films are promoted with some catalysts selected from Pt-group metals (Pt, Pd, Ru or any combination of these metals) they exhibit a high sensitivity and selectivity to hydrogen gas. Unlike other metal oxide sensors which are sensitive to many reducing and oxidizing gases and operate at a temperature of 350 C or higher; this sensor is highly selective to hydrogen gas and its operating temperature is from 25 to 150C. The lower operating temperature enhances safety when dealing with hydrogen gas. The sensor response to hydrogen at 120 C is linear in concentration from 30 to 104 ppm with a 10 to 30 second response time and a 45 to 90 second recovery time. Above 104 ppm the sensor is still linear but the slope of conductance versus hydrogen concentration changes.

Miremadi, Bijan K.; Singh, Ravi C.; Morrison, S. Roy; Colbow, Konrad

1996-09-01

45

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

PubMed

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

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

2010-11-01

46

Study on ZnO-doped tin oxide thick film gas sensors  

Microsoft Academic Search

The effect of ZnO doping in SnO2 was investigated for gas sensor applications. Zinc oxide in different concentration, 2wt% and 5wt% was added to tin oxide powder prepared by a co-precipitation method. The gas sensor was made on alumina substrate by the screen-printing technique. The sensitivity for different gases such as methane, LPG, ethanol and CO gases was investigated at

Abhilasha Srivastava; Rashmi; Kiran Jain

2007-01-01

47

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

48

Ethanol gas sensors based on copper phthalocyanine thin-film transistors  

Microsoft Academic Search

A bottom contact copper phthalocyanine (CuPc) based organic thin film transistor (OTFT) was fabricated in this paper. CuPc thin film acting both as gas sensing layer and the active layer was formed by vacuum evaporation and was characterized by scanning electron microscope(SEM). The results show that the film is highly ordered and has a polycrystalline morphology. The current-voltage characteristics of

Xian Li; Ya-Dong Jiang; Guang-Zhong Xie; Xiao-Song Du; Hui-Ling Tai; Jian-Fei Yan; Song-Qi Fu

2010-01-01

49

A self-heating gas sensor with integrated NiO thin-film for formaldehyde detection  

Microsoft Academic Search

This study develops a MEMS-based formaldehyde gas sensor based on a suspended silicon nitride microstructure with an integrated micro Pt heater, a thin-film NiO sensing layer and Pt interdigitated electrodes (IDEs) to measure the resistance changes of the NiO layer in the presence of formaldehyde. A specific orientation of the NiO layer is observed as the substrate temperature in the

Chia-Yen Lee; Che-Ming Chiang; Yu-Hsiang Wang; Rong-Hua Ma

2007-01-01

50

Hydrogen-selective thermoelectric gas sensor  

Microsoft Academic Search

A thermoelectric (TE) hydrogen gas sensor was fabricated by depositing a platinum catalyst thin film on the half surface of nickel oxide thick film. When it was exposed to combustible gas diluted by synthetic air, the catalyst layer converts hydrogen and oxygen effectively to water vapor, and give out heat energy, resulting temperature difference across the sensor, and consequently voltage

Woosuck Shin; Masahiko Matsumiya; Noriya Izu; Norimitsu Murayama

2003-01-01

51

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

52

Spray-pyrolized nanostructured CuO thin films for H2S gas sensor  

NASA Astrophysics Data System (ADS)

Nanostructured copper oxide (CuO) thin films were prepared by spray pyrolysis technique. X-ray diffraction was used to investigate the structural properties. Surface morphology was studied using scanning electron microscopy. Microstructure was studied using a transmission electron microscope, and energy-dispersive X-ray analysis was used to determine the elemental composition of prepared nanostructured CuO thin film. Gas-sensing performance was conducted using static gas-sensing system, at different operating temperatures in the range of 200C to 400C for the gas concentration of 100 ppm. The maximum sensitivity ( S = 872) to H2S was found at the temperature of 250C. Quick response (2 s) and fast recovery (5 s) are the main features of this film.

Bari, Ramesh H.; Patil, Sharad B.; Bari, Anil R.

2013-03-01

53

Room Temperature ppb Level Chlorine Gas Sensor Based on Copper (II) 1, 4, 8, 11, 15, 18, 22, 25-octabutoxy-29 H, 31 H-phthalocyanine Films  

SciTech Connect

Spin coating technique has been used to fabricate room temperature chlorine gas sensor based on copper (II) 1, 4, 8, 11, 15, 18, 22, 25-octabutoxy-29 H, 31 H-phthalocyanine (CuPc(OBu){sub 8}) films. Gas sensor shows a response of 185% to few parts per billion level of Cl{sub 2} gas with response time of 9.5 minutes at room temperature. The interactions between sensor and analytes followed first order kinetics with rate constant 0.01{<=}k{<=}0.02. The chemiresistive sensor showed very good stability at room temperature over a long period of time.

Bedi, R. K.; Saini, Rajan; Mahajan, Aman [Material Science Laboratory, Department of PhysicsGuru Nanak Dev University, Amritsar-143005 (India)

2010-12-01

54

Gas sensor based on nano ZSM-5 zeolite films for the nerve agent simulant dimethylmethylphosphonate detection  

NASA Astrophysics Data System (ADS)

The piezoelectric sensor device coated with nanosize ZSM-5 zeolite films has beem fabricated. The Nerve agent simulant Dimethylmethylphosphonate has been tested with this piezoelectric sensor devices. The frequency shifts to time at 1 ppm, 5ppm and 20ppm DMMP are examined respectively. The minimum detection concentration of 1ppm DMMP has been obtained in the N2 at 293K. 1 ppm is lower than the EC50 concentration value (where EC50 is the airborne concentration sufficient to induce severe effects in 50% of those exposed for 30 min). The frequency sensitivity was found to be about 60HZ / ppm. The effect of acetone on the ZSM-5 zeolite film was also investigated for the selectivity test. Using principle component analysis (PCA), we can qualify and quantify these testing gases.

Xie, Haifen; Ting, Yu; Sun, Xiaoxiang; Jia, Zhou; Huang, Yiping

2004-12-01

55

Fabrication of a gas sensor array with micro-wells for VOCs gas sensing based on polymer/carbon nanotube thin films  

NASA Astrophysics Data System (ADS)

In this paper, gas sensor array with micro-well was designed and prepared by Micro Electro-Mechanical Systems (MEMS) technology. The micro-well and interdigital electrodes of sensor array were prepared using photolithography process, reactive ion etching (RIE) process, wet etching and conventional vacuum evaporation. In the manufacture process of the gas sensor array, KOH wet etching process was mainly discussed. The optimum etching processing parameters were as follows: 30 wt% KOH solution at 80 C, a cooling back-flow device and a magnetic stirrer. The multi-walled carbon nanotubes (MWCNTs)-polyethyleneoxide (PEO) and MWNTs-Polyvinylpyrrolidone (PVP) composite films were utilized as sensitive layers to test gas-sensing properties. Response performances of MWCNTs- PEO and MWNTs-PVP composite films to toluene vapor and methanol vapor at room temperature were investigated. The results revealed that the sensor array showed a larger sensitivity to toluene vapor than to methanol vapor. In addition, the sensing mechanisms were studied as well.

Xie, Guangzhong; Xie, Tao; Zhu, Tao; Jiang, Yadong; Tai, Huiling

2014-08-01

56

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

57

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

58

Micro-gas-sensor with conducting polymers  

Microsoft Academic Search

In this paper design and fabrication of micro-gas-sensors, the deposition of four different poly(pyrrole) (PPY) thin films as chemoresistor in the micro-gas-sensors by electrochemical processing and chemical oxidation, and characterisation these films by FTIR, SEM, surface test instrument (WYKO NT2000) and optical microscopy, are reported. The effect of anions in PPY thin films, thickness and surface roughness of the PPY

Q. Fang; D. G. Chetwynd; J. A. Covington; C.-S. Toh; J. W. Gardner

2002-01-01

59

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

60

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

61

Development of Oxide Semiconductor Thick Film Gas Sensor for the Detection of Total Volatile Organic Compounds  

NASA Astrophysics Data System (ADS)

After an amendment of Building Standards Law in 2003, the installation of the ventilator is compulsory in the newly built house. Because many persons suffer from indoor-air pollutants caused by the volatile organic compounds (VOCs). The final purpose of this research is to develop the gas sensor which can monitor the gross weight of VOC gases indoors and then to control the ventilator efficiently using the sensor. In order to develop the sensor which detects total VOC, the responses of 4 oxide semiconductor materials to 37 kinds of VOC gases were studied. Those materials showed small responses to halogenated and aliphatic hydrocarbon gases. As a result of improving the response to these gases, among 4 metal oxides examined, SnO2 and WO3 showed high sensitivities by the addition of Pd and Pt. The sensing properties of SnO2 for halogenated hydrocarbon gases were extremely improved by the addition of 0.5wt% Pd. Also, the sensing properties of SnO2 for aliphatic hydrocarbon gases were improved by the addition of 0.7wt% Pt. In addition, the doubly promoted element, Pt(0.5wt%)-Pd(0.5wt%)-SnO2, showed a large response to many kinds of VOC gases examined.

Kadosaki, Masahiro; Sakai, Yuichi; Tamura, Ikuo; Matsubara, Ichiro; Itoh, Toshio

62

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

Microsoft Academic Search

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

A. Diguez; A. Romano-Rodr??guez; J. R. Morante; J. Kappler; N. Brsan; W. Gpel

1999-01-01

63

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

Microsoft Academic Search

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

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

2007-01-01

64

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

65

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 500C 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

66

The selective detection of C 2H 5OH using SnO 2ZnO thin film gas sensors prepared by combinatorial solution deposition  

Microsoft Academic Search

Sensing materials for selective detection of C2H5OH were designed using combinatorial solution deposition of SnO2ZnO thin films. The SnO2ZnO composite sensor prepared by alternate deposition of 10 droplets of SnO2 and ZnO sols (S50Z50 sensor) showed a high response to 200ppm C2H5OH (S(ethanol)=Ra\\/Rg=4.69, Ra: resistance in air, Rg: resistance in gas) at 300C, while the gas responses to 100ppm C3H8,

Ki-Won Kim; Pyeong-Seok Cho; Sun-Jung Kim; Jong-Heun Lee; Chong-Yun Kang; Jin-Sang Kim; Seok-Jin Yoon

2007-01-01

67

SAW ethanol gas sensors based on cryptophane-A sensitive film  

Microsoft Academic Search

Surface acoustic wave (SAW) devices have been widely used for various chemical sensing applications because the sensor signal can be detected by simple and inexpensive electronics. The interactions between target analyte and the sensor surface cause changes in the mechanical, electrical, dielectric properties of the sensing coating deposited onto acoustic transducer. The changes in these properties will lead to changes

Ping Sun; Yadong Jiang; Guangzhong Xie; Xiaosong Du

2010-01-01

68

Copper-doping level effect on sensitivity and selectivity of tin oxide thin-film gas sensor  

Microsoft Academic Search

The influence of doping level of basic material on electrical resistance controlled by gas chemisorption is investigated experimentally for chemically deposited tin oxide thin films with different amounts of Cu and Sb additives. Significant modification of dependences of resistance versus temperature in oxygen-rich atmosphere and anomalous change of selectivity of resistance response to CO and H2 gas are obtained by

A. Galdikas; A. Mironas; A. etkus

1995-01-01

69

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 ) 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 ) onto WO 3 thin films and then the films as-deposited were annealed at 400C 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 200C operating temperature. Especially,in case 300 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

70

Sensor photoresponse of thin-film oxides of zinc and titanium to oxygen gas  

SciTech Connect

Response of steady-state photoconductivity to changes in oxygen partial pressure (10{sup {minus}3} to 1 atm) has been quantitatively studied in thin-film polycrystalline TiO{sub 2}:Nb and ZnO at 80--120 C. The magnitude of photoconductivity varied as a square root of illumination intensity regardless of oxygen pressure. Both materials showed fast response to oxygen, although in different pressure ranges. Zinc oxide was more sensitive to lower oxygen pressures while titanium dioxide worked better at pressures close to 1 atm.

Golego, N.; Studenikin, S.A.; Cocivera, M.

2000-04-01

71

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

72

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

PubMed

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

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

2011-01-01

73

MEMS-based hydrogen gas sensors  

Microsoft Academic Search

The widespread use of hydrogen as both an industrial process gas and an energy storage medium requires fast, selective detection of hydrogen gas. This paper reports the development of a new type of solid-state hydrogen gas sensor that couples novel metal hydride thin films with a micro-electro-mechanical system (MEMS) structure known as a micro-hotplate. Micro-hotplate structures are fabricated via surface

Frank DiMeo; Ing-Shin Chen; Philip Chen; Jeffrey Neuner; Andreas Roerhl; James Welch

2006-01-01

74

TiPc2\\/Pt Ultra-Thin Film Sandwich Structure for Low Temperature Gas Sensor  

Microsoft Academic Search

The novel gas-sensitive structures consisting of top-layer of titanium bis-phtalocyaninate and ultra-thin bottom-layer of Pt were developed. The chemical composition of the samples was studied by combining XPS analysis with cyclic Ar+ etching. The resistance response of TiPc2\\/Pt structures to gases was examined. The investigated samples were detecting H2 and NOx in air at the temperatures of 20 - 150

A. Capobianchi; M. P. Casaletto; S. Kaciulis; G. Mattogno; L. Pandolfi; G. Pennesi; A. Galdikas; A. Mironas; A. Setkus

2000-01-01

75

ANN Modeling of Micro-Machined Gas Sensor Signals  

Microsoft Academic Search

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

Mohamed Gamal El-din; Walied A. Moussa

2005-01-01

76

Thin-film sensors for space propulsion technology  

NASA Astrophysics Data System (ADS)

SSME components such as the turbine blades of the high pressure fuel turbopump are subjected to rapid and extreme thermal transients that contribute to blade cracking and subsequent failure. The objective was to develop thin film sensors for SSME components. The technology established for aircraft gas turbine engines was adopted to the materials and environment encountered in the SSME. Specific goals are to expand the existing thin film sensor technology, to continue developing improved sensor processing techniques, and to test the durability of aircraft gas turbine engine technology in the SSME environment. A thin film sensor laboratory is being installed in a refurbished clean room, and new sputtering and photoresist exposure equipment is being acquired. Existing thin film thermocouple technology in an SSME environment are being tested. Various coatings and their insulating films are being investigated for use in sensor development.

Kim, W. S.; Englund, D. R.

1985-05-01

77

Thin-film Sensors for Space Propulsion Technology  

NASA Technical Reports Server (NTRS)

SSME components such as the turbine blades of the high pressure fuel turbopump are subjected to rapid and extreme thermal transients that contribute to blade cracking and subsequent failure. The objective was to develop thin film sensors for SSME components. The technology established for aircraft gas turbine engines was adopted to the materials and environment encountered in the SSME. Specific goals are to expand the existing thin film sensor technology, to continue developing improved sensor processing techniques, and to test the durability of aircraft gas turbine engine technology in the SSME environment. A thin film sensor laboratory is being installed in a refurbished clean room, and new sputtering and photoresist exposure equipment is being acquired. Existing thin film thermocouple technology in an SSME environment are being tested. Various coatings and their insulating films are being investigated for use in sensor development.

Kim, W. S.; Englund, D. R.

1985-01-01

78

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

PubMed

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

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

2013-01-01

79

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

PubMed

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

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

2014-01-22

80

Optical-integrated NH 3 sensor design based on WO 3 thin films: influence of gas adsorption and chromic effects  

NASA Astrophysics Data System (ADS)

It has been observed in the literature, developments about characterization of several materials for gas sensing application; simultaneously, also it has been observed that only some of them show a procedure of design for the implementation of these materials in a device or an optical system. In consequence, appears differences between the predicted by theory and the experiments. For that reason, the present work proposes a new approach for the design of optical-integrated (OI) sensors. We show the advances in the design of an OI sensor for ammonia detection (NH 3), using tungsten trioxide (WO 3) as sensitive material. We considered a model that incorporates the concepts of the kinetic of gas adsorption on solids, the effects of the real and imaginary part of the refractive index in the redistribution of the optical field, and the influence of the photo and thermochromism, before and during the sensing mechanism. Although the work has not been concluded, we can affirm that the concepts incorporated in this proposal, must be considered as critical parameters in the design of an OI sensor or an optical fiber (FO) sensor.

Lazcano Hernndez, Hugo E.; Snchez Prez, Celia; Garca Valenzuela, Augusto; Esparza Garca, Alejandro; Camacho Lpez, Marco A.

2007-03-01

81

Analog signal-selector circuit for quick gas detection from gas-sensor arrays  

Microsoft Academic Search

A Sixteen Input Maximum\\/Minimum Analog signal-selector Circuit (SIMMAC) is designed, simulated, and implemented using 2 ?m p-well (Orbit) CMOS technology. The circuit is useful in recognition of gas types from measurements of thin-film gas-sensor arrays. The output signal of each thin-film gas detector is typically a function of bias voltages, temperature and pressure, film type, frequency, and gas type. Gas

Hoda S. Abdel-ALy-Zohdy; Fatma A. El-Licy

1995-01-01

82

Microhotplate gas sensor arrays  

NASA Astrophysics Data System (ADS)

In this work, micromachining and planar processing have been used to produce gas sensing devices with lower power consumption at lower cost. The small size brings new advantages for chemical selectivity as well: multi-element arrays whose time-varying signals can be interpreted using pattern recognition methods. The device platform is a `microhotplate,' consisting of a built-in heater, thermometer, and electrodes to probe the sensing films. Microhotplates are fabricated using CMOS-compatible technologies, enabling on-chip circuitry for multiplexing and signal amplification.

Cavicchi, Richard E.; Semancik, Stephen; Walton, Robin M.; Panchapakesan, Balaji; DeVoe, Don L.; Aquino-Class, Maria I.; Allen, James D.; Suehle, John S.

1999-11-01

83

Bimodular high temperature planar oxygen gas sensor.  

PubMed

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 800C 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

84

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 800C 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

85

Progress on thin-film sensors for space propulsion technology  

NASA Astrophysics Data System (ADS)

The objective is to develop thin-film thermocouples for Space Shuttle Main Engine (SSME) components. Thin-film thermocouples have been developed for aircraft gas turbine engines and are in use for temperature measurement on turbine blades to 1800 F. The technology established for aircraft gas turbine engines will be adapted to the materials and environment encountered in the SSME. Specific goals are to expand the existing in-house thin-film sensor technology and to test the survivability and durability of thin-film sensors in the SSME environment.

Kim, Walter S.

86

Progress on thin-film sensors for space propulsion technology  

NASA Technical Reports Server (NTRS)

The objective is to develop thin-film thermocouples for Space Shuttle Main Engine (SSME) components. Thin-film thermocouples have been developed for aircraft gas turbine engines and are in use for temperature measurement on turbine blades to 1800 F. The technology established for aircraft gas turbine engines will be adapted to the materials and environment encountered in the SSME. Specific goals are to expand the existing in-house thin-film sensor technology and to test the survivability and durability of thin-film sensors in the SSME environment.

Kim, Walter S.

1987-01-01

87

Sensitivity and stability of porous polycrystalline silicon gas sensor  

Microsoft Academic Search

Porous silicon (PS) used as a sensing material for micro-sensors has attracted a lot of attention in recent years. Owing to the large surface area (?200 m2 cm?3) and high chemical activity, porous silicon would be a good choice for gas sensor applications. In this paper, a resistivity sensor using porous polycrystalline silicon (PPS) thin films was fabricated by anodization

P. G Han; H Wong; M. C Poon

2001-01-01

88

ZnO Thin Film Ga s Sensor for CO  

SciTech Connect

ZnO thin films were deposited onto corning glass substrates by rf magnetron sputtering system using ZnO targets. Films were deposited under rf power of 80 W at various deposition time. The distance between the target and substrate was held at 45 cm. A mixed Ar and O{sub 2} gas was introduced into the chamber at 4x10{sup -2} Torr. The structure of the deposited ZnO films was investigated by Scanning electron miscroscopy. The gas sensing properties were evaluated at various operation temperatures by measuring the changes of resistance of the sensor in air and in CO gas respectively using the gas sensing characterization system. The grain size was increased as the film thickness was increased during deposition. The sensor with 233 nm film thickness exhibited the highest sensitivity for CO gas.

Manap, Y. A.; Ismail, B.; Yusuf, M. N. M.; Shamsuri, W. N. W.; Wahab, Y.; Othaman, Z. [Department of Physics, Faculty of Science, University of Technology Malaysia, Skudai, Johor (Malaysia)

2010-03-11

89

Resonance-Shift Gas Pressure Sensors Based on Bulk PZT  

Microsoft Academic Search

A resonance-shift pressure sensor was designed and fabricated using MEMS technology in order to detect gas flow pressure. The pressure sensor is made of silicon and Pyrex glass, and is actuated by a piece of bulk PZT with the thickness of 191 m. An actuation element for silicon thin film and gas flow pressure change the frequency of fundamental mode

Yi-Chu Hsu; Ming-Can Wu; Ling-Sheng Jang

90

Surface chemistry of tin oxide based gas sensors  

Microsoft Academic Search

Four types of gas sensors based on SnOx thin film with and without additives (Pt and Sb) were investigated by means of x-ray photoelectron spectroscopy and scanning Auger microscopy. The sensors were deposited on Si substrates by using reactive dc magnetron sputtering. The temperature dependencies of the electrical resistivity response to CO gas exposure were measured in order to characterize

G. Gaggiotti; A. Galdikas; S. Kaciulis; G. Mattogno; A. Setkus

1994-01-01

91

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

92

Novel array-type gas sensors using conducting polymers, and their performance for gas identification  

Microsoft Academic Search

Novel gas sensor devices have been developed using polythiophene (pTh) film and poly(3-n-dodecylthiophene) (pDpTh) film coated over pTh film. These polymer films were electrochemically deposited and doped by cyclic voltammetry on thin-film electrodes where the isolation gap was formed by a micromachining process. We examined the response characteristics of the conducting polymer films against various sample gases over a range

Yoshiaki Sakurai; Ho-Sup Jung; Toshinori Shimanouchi; Takao Inoguchi; Seiichi Morita; Ryoich Kuboi; Kazuki Natsukawa

2002-01-01

93

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

94

Binary MEMS gas sensors  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

95

Porous silicon ammonia gas sensor  

NASA Astrophysics Data System (ADS)

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

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

2006-04-01

96

Sensing mechanism of polymer for selectivity enhancement of gas sensors  

Microsoft Academic Search

The sensing mechanism of polymer gas separation membrane to enhance the selectivity of tin dioxide gas sensors is presented. Two types of Commercial polymers, XU218 and PMDA-ODA of Ciba-Geigy company, are used to coat onto the sensing film of FIGARO series tin dioxide gas sensors TGS800, TGS813 and TGS842. Different gases such as carbon monoxide, hydrogen, methane, and ammonia are

Kenneth K. L. Wong; Zhenan Tang; J. K. O. Sin; P. C. H. Chan; P. W. Cheung; Hiroyuki Hiraoka

1996-01-01

97

Solid state gas sensor research in Germany - a status report.  

PubMed

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

98

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

99

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

100

Exhaust gas sensors  

SciTech Connect

The automotive industry needed a fast, reliable, under-the-hood method of determining nitrogen oxides in automobile exhaust. Several technologies were pursued concurrently. These sensing technologies were based on light absorption, electrochemical methods, and surface mass loading. The Y-12 plant was selected to study the methods based on light absorption. The first phase was defining the detailed technical objectives of the sensors--this was the role of the automobile companies. The second phase was to develop prototype sensors in the laboratories--the national laboratories. The final phase was testing of the prototype sensors by the automobile industries. This program was canceled a few months into what was to be a three-year effort.

Hiller, J. [Lockheed Martin Energy Systems, Inc., Oak Ridge, TN (United States); Miree, T.J. [Ford Motor Co., Allen Park, MI (United States)

1997-02-09

101

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

102

Fast temperature programmed sensing for micro-hotplate gas sensors  

Microsoft Academic Search

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

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

1995-01-01

103

TiO 2 thin films by a novel solgel 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 solgel technique. Nanostructured films of pure TiO2 in the anatase form are obtained after annealing at 500C. 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

104

Thin Hot-Film Sensors On Polyimide Film  

NASA Technical Reports Server (NTRS)

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

Hopson, Purnell

1993-01-01

105

SELECTIVE FILTER FOR SnO2 BASED GAS SENSOR : APPLICATION TO HYDROGEN TRACE DETECTION  

E-print Network

1 SELECTIVE FILTER FOR SnO2 BASED GAS SENSOR : APPLICATION TO HYDROGEN TRACE DETECTION G Saint-Etienne, France email: tournier@emse.fr ABSTRACT The main drawback of the SnO2 based gas sensors sensitivity to ethanol, methane, carbon monoxide and hydrogen sulfide. Thick film SnO2 sensors are treated

Paris-Sud XI, Université de

106

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; Brtz, Joachim; Gurlo, Aleksander; Arveux, Emmanuel; Klein, Andreas; Toupance, Thierry

2012-10-01

107

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

PubMed

Nanocrystalline tin dioxide (SnO(2)) 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 SnO(2) 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 H(2) 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. PMID:23011110

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

2012-11-01

108

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

Microsoft Academic Search

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

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

1997-01-01

109

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

110

GAS SENSOR APPLICATION OF CARBON NANOTUBES  

Microsoft Academic Search

Gas sensors have a wide application in everyday life, whether in industry, medical, agriculture and environmental monitoring. A good sensor should be selective, sensitive, responsive, reliable and cost effective. Currently available gas sensors are lacking in one or more of these criteria. Therefore, there is a need to develop new sensing materials and technologies. Carbon nanotubes (CNTs) have the potential

M. Y. Faizah; A. Fakhru' l-Razi; R. M. Sidek; A. G. Liew Abdullah

2007-01-01

111

Enhanced Sensing Characteristics in MEMS-based Formaldehyde Gas Sensor  

E-print Network

This study has successfully demonstrated a novel self-heating formaldehyde gas sensor based on a thin film of NiO sensing layer. A new fabrication process has been developed in which the Pt micro heater and electrodes are deposited directly on the substrate and the NiO thin film is deposited above on the micro heater to serve as sensing layer. Pt electrodes are formed below the sensing layer to measure the electrical conductivity changes caused by formaldehyde oxidation at the oxide surface. Furthermore, the upper sensing layer and NiO/Al2O3 co-sputtering significantly increases the sensitivity of the gas sensor, improves its detection limit capability. The microfabricated formaldehyde gas sensor presented in this study is suitable not only for industrial process monitoring, but also for the detection of formaldehyde concentrations in buildings in order to safeguard human health.

Wang, Yu-Hsiang; Lee, Chia-Yen; Ma, R -H; Chou, Po-Cheng

2008-01-01

112

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

Microsoft Academic Search

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

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

2007-01-01

113

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.

Rei, Sebastian; Hagen, Gunter; Moos, Ralf

2008-01-01

114

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

115

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

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

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

118

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

Microsoft Academic Search

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

A Galdikas; A Mironas; V Janickis

2000-01-01

119

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

120

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

121

Improvements to Zirconia Thick-Film Oxygen Sensors  

NASA Astrophysics Data System (ADS)

Thick-film zirconia gas sensors are normally screen-printed onto a planar substrate. A sandwich of electrode-electrolyte-electrode is fired at a temperature sufficient to instigate sintering of the zirconia electrolyte. The resulting porous zirconia film acts as both the electrolyte and as the diffusion barrier through which oxygen diffuses. The high sintering temperature results in de-activation of the electrodes so that sensors must be operated at around 800 C for measurements in the percentage range of oxygen concentration. This work shows that the use of cobalt oxide as a sintering aid allows reduction of the sensor operating temperature by 100-200 C with clear benefits. Furthermore, an interesting and new technique is presented for the investigation of the influence of dopants and of the through-porosity of ionically-conducting materials.

Maskell, William C.; Brett, Daniel J. L.; Brandon, Nigel P.

2013-06-01

122

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

PubMed Central

Very often, high-temperature operated gas sensors are cross-sensitive to oxygen and/or they cannot be operated in oxygen-deficient (rich) atmospheres. For instance, some metal oxides like Ga2O3 or doped SrTiO3 are excellent materials for conductometric hydrocarbon detection in the rough atmosphere of automotive exhausts, but have to be operated preferably at a constant oxygen concentration. We propose a modular sensor platform that combines a conductometric two-sensor-setup with an electrochemical pumping cell made of YSZ to establish a constant oxygen concentration in the ambient of the conductometric sensor film. In this paper, the platform is introduced, the two-sensor-setup is integrated into this new design, and sensing performance is characterized. Such a platform can be used for other sensor principles as well. PMID:22423212

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

2009-01-01

123

Integrated interface circuit with multiplexed input and digital output for a 5 5 SnO 2 thick film gas-sensor matrix  

Microsoft Academic Search

This paper presents the design and experimental results for a 55 tin-oxide gas-sensor array system with particular focus on the employed multiplexed-analog-input 0.35?m CMOS interface circuit chip. This interface circuit reads the electrical signal of all the elements of the array in time sharing by means of a solid-state selector, actually exploiting a row-column query technique and provides digital output

M. Grassi; P. Malcovati; L. Francioso; P. Siciliano; A. Baschirotto

2008-01-01

124

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 polyvinilydene fluoride (PVDF) thin-film photopy- roelectric (PPE) sensors [1,2]. The PPE sensor exhibits-4005(98)00137-3 #12;A. Mandelis, J.A. Garcia / Sensors and Actuators B 49 (1998) 258­267 259 posed an optical

Mandelis, Andreas

125

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

126

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

127

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

128

All thin film magnetoelectric magnetic field sensors.  

NASA Astrophysics Data System (ADS)

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

Zhao, Peng

2009-03-01

129

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

130

Integrated read-out and temperature control interface with digital I\\/O for a gas-sensing system based on a SnO2 microhotplate thin film gas sensor  

Microsoft Academic Search

A complete gas-sensing system for portable ambient monitoring purpose, consisting of a sensor (with embedded heater and thermometer) and an integrated interface (with read-out channel and closed-loop temperature control circuit) is presented. The micromachined sol-gel tin-oxide sensor features a 450 nm thick silicon nitride\\/oxide membrane, an active area of 170 mum times 170 mum and a power consumption of 25

A. Lombardi; L. Bruno; M. Grassi; P. Malcovati; S. Capone; L. Francioso; P. Siciliano; A. Baschirotto

2008-01-01

131

Gas sensors for refractive index detection using surface plasmon resonance on nanosystem  

NASA Astrophysics Data System (ADS)

A plasmonic device for gas sensor is investigated for refractive index detection using surface plasmon resonance (SPR). The sensor device consists of nano-cavity antennas formed by metallic rectangular nanostrip array over a metal film, which monitors the changes of the refractive index by measuring the spectral shift of the resonance angle dip. The average detection sensitivity of the gas sensor is about 136 / RIU (refractive index units) for SPR excitation at 1550 nm telecommunication wavelength.

Zhao, Hua-Jun; Tian, Yong-You; Lei, Ju-Hua

2014-07-01

132

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

Microsoft Academic Search

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

Herbert Will

1991-01-01

133

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

134

Oxide Nanobelts as Conductometric Gas Sensors  

Microsoft Academic Search

Semiconducting oxide nanobelts have been obtained by vapor phase deposition. In this work we present the results obtained using tin oxide nanobelts as conductometric gas sensors. Electrical characterization showed that the nanobelts were sensitive to oxygen and environmental polluting species such as CO as well as ethanol for breath analyzers and food control applications. The sensor response, defined as the

E. Comini; G. Faglia; G. Sberveglieri; L. Zanotti

2006-01-01

135

Design and development of multiple sensor array based on SnO2 thin films for e-nose application  

NASA Astrophysics Data System (ADS)

Fabrication of a 2 4 multiple sensor array based on SnO2 thin films was demonstrated. SnO2 thin films were deposited on Al2O3 substrates and modified selectively using Au and CuO by sputtering. The sensor array was tested for its gas sensing characteristics towards H2S. The maximum sensor response (S=52) was observed in case of Au modified SnO2 thin films. By the surface modification using Au there is increase in the sensor response at all temperature. With the increase in temperature, sensor response decreases.

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

2013-06-01

136

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

137

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 400C. 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

138

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

139

Thermal Sensor Arrays for The Combinatorial Analysis of Thin Films  

E-print Network

Thermal Sensor Arrays for The Combinatorial Analysis of Thin Films A dissertation presented Advisor Author Joost J. Vlassak Patrick J. McCluskey Thermal Sensor Arrays for The Combinatorial Analysis of Thin Films Abstract Membrane-based thermal sensor arrays were developed for the high- throughput

140

Graphene nanomesh as highly sensitive chemiresistor gas sensor.  

PubMed

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

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

2012-10-01

141

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

142

Inkjet-Printed Graphene-Based Wireless Gas Sensor Modules , Vasileios Lakafosis1  

E-print Network

sensor when exposed to different types of gases, including the hard-to-detect CO gas, that can-powered, battery-less, wireless sensor solutions utilizing thin films produced from environmentally friendly, water% sensitivity was obtained at 864 MHz using functionalized multi walled CNT (MWCNT) dissolved in water

Tentzeris, Manos

143

Investigation of the electrode effects in mixed potential type ammonia exhaust gas sensors  

Microsoft Academic Search

Mixed potential ammonia exhaust gas sensors provide a high capability for applications in harsh environments when appropriate means are conducted to stabilize the electrodes catalytic activity. The discussed sensor utilizes oxygen ion conducting yttria stabilized zirconia and gold electrodes, one of which is covered with an SCR active film to establish ammonia sensitivity and selectivity. The used SCR catalyst is

Daniela Schnauer; Thomas Nieder; Kerstin Wiesner; Maximilian Fleischer; Ralf Moos

2011-01-01

144

Biomaterial based sulphur di oxide gas sensor  

NASA Astrophysics Data System (ADS)

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

Ghosh, P. K.; Sarkar, A.

2013-06-01

145

A Novel Graphene-Based Inkjet-Printed WISP-Enabled Wireless Gas Sensor  

E-print Network

A Novel Graphene-Based Inkjet-Printed WISP- Enabled Wireless Gas Sensor Taoran Le, Vasileios thin films produced from environmentally friendly, water-based, inkjet printed graphene oxide (GO) ink is achieved using the graphene thin films, with over 30% of material recovery observed within 5 minutes

Tentzeris, Manos

146

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

147

Boundary layer measurements using hot-film sensors  

NASA Technical Reports Server (NTRS)

Measurements in the aerodynamic boundary layer using heat transfer, hot-film sensors are receiving a significant amount of effort at the Langley Research Center. A description of the basic sensor, the signal conditioning employed, and several manifestations of the sensor are given. Results of a flow reversal sensor development are presented, and future work areas are outlined.

Holmes, Harlan K.; Carraway, Debra L.

1986-01-01

148

Graphene Based Flexible Gas Sensors  

NASA Astrophysics Data System (ADS)

Graphene is a novel carbon material with great promise for a range of applications due to its electronic and mechanical properties. Its two-dimensional nature translates to a high sensitivity to surface chemical interactions thereby making it an ideal platform for sensors. Graphene's electronic properties are not degraded due to mechanical flexing or strain (Kim, K. S., et al. nature 07719, 2009) offering another advantage for flexible sensors integrated into numerous systems including fabrics, etc. We have demonstrated a graphene NO2 sensor on a solid substrate (100nm SiO2/heavily doped silicon). Three different methods were used to synthesize graphene and the sensor fabrication process was optimized accordingly. Water is used as a controllable p-type dopant in graphene to study the relationship between doping and graphene's response to NO2 . Experimental results show that interface water between graphene and the supporting SiO2 substrate induces higher p-doping in graphene, leading to a higher sensitivity to NO2, consistent with theoretical predications (Zhang, Y. et al., Nanotechnology 20(2009) 185504). We have also demonstrated a flexible and stretchable graphene-based sensor. Few layer graphene, grown on a Ni substrate, is etched and transferred to a highly stretchable polymer substrate (VHB from 3M) with preloaded stress, followed by metal contact formation to construct a flexible, stretchable sensor. With up to 500% deformation caused by compressive stress, graphene still shows stable electrical response to NO2. Our results suggest that higher compressive stress results in smaller sheet resistance and higher sensitivity to NO2. A possible molecular detection sensor utilizing Surface Enhanced Raman Spectrum (SERS) based on a graphene/gallium nanoparticles platform is also studied. By correlating the enhancement of the graphene Raman modes with metal coverage, we propose that the Ga transfers electrons to the graphene creating local regions of enhanced electron concentration modifying the Raman scattering in graphene.

Yi, Congwen

149

Carnegie Mellon Polythiophene-Based Gas Chemical Sensors for  

E-print Network

Carnegie Mellon Polythiophene-Based Gas Chemical Sensors for Detecting End-Bed Preliminary Testing Gas sampling Test-bed at NIOSH Gas Chromatograph Capped chemiresistor A sensor chip developed to systematically evaluate sensors embedded within carbon filter beds. Gas analyte concentrations

Weiss, Lee E.

150

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

151

A Low Voltage Gas Ionization Sensor based on Sparse Gold Nanorods  

Microsoft Academic Search

We report fabrication and characterization of a gas ionization sensor using a sparse array of vertically aligned gold nanorods (AuNR). Our device displayed improved sensitivity compared to the carbon nanotube (CNT) film counterpart, since the room temperature breakdown voltages (Vb) of the tested gases were further reduced. With AuNRs configured as the cathode, Vb was unaffected by gas pressure within

Ramin Banan Sadeghian; Mojtaba Kahrizi

2007-01-01

152

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

153

Combined Seebeck and resistive SnO 2 gas sensors, a new selective device  

Microsoft Academic Search

Simultaneous measurements of electrical resistance R and Seebeck e.m.f. Vs of thick film SnO2 gas sensors were performed in air containing different concentrations pi of reducing gas (ethanol vapours, CO, CH4, C2H6 were successively used). The graphical representations of the Vs versus lnh values both for the identification of the reducing gas (selectivity) and for the determination of gas concentration.

Radu Ionescu

1998-01-01

154

Sensors and Actuators B 108 (2005) 6269 Effect of in-flight annealing and deposition method on gas-sensitive  

E-print Network

Sensors and Actuators B 108 (2005) 62­69 Effect of in-flight annealing and deposition method on gas influence the nor- malized conductance of SnO2 thin film gas sensors [7]. How- ever, this can be due structure, surface stoichiometry and normalized conductance in ethanol-containing air was investigated

Lorke, Axel

155

Development of measuring method for oil film pressure of engine main bearing by thin film sensor  

Microsoft Academic Search

In this study, a thin film pressure sensor made of manganin was developed by means of sputtering. The sensor was formed directly on the sliding surface of a plain bearing, and oil film pressure measurement during engine operation was carried out successfully. The formation method and characteristics of the sensor are presented in this paper, together with the measured data,

Yuji Mihara; Takahiro Hayashi; Motoyoshi Nakamura; Tsuneo Someya

1995-01-01

156

Conduction Model of Metal Oxide Gas Sensors  

Microsoft Academic Search

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

Nicolae Barsan; Udo Weimar

2001-01-01

157

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

158

Micromachined metal oxide gas sensors: opportunities to improve sensor performance  

Microsoft Academic Search

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

Isolde Simon; Nicolae Brsan; Michael Bauer; Udo Weimar

2001-01-01

159

Exhaust Gas Sensor Based On Tin Dioxide For Automotive Application  

E-print Network

Exhaust Gas Sensor Based On Tin Dioxide For Automotive Application Arthur VALLERON a,b , Christophe, Engineering Materials Department The aim of this paper is to investigate the potentialities of gas sensor layer with gold electrodes. This gas sensor is able to detect both reducing and oxidizing gases

Paris-Sud XI, Université de

160

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

161

An optically integrated NH3 sensor using WO3 thin films as sensitive material  

NASA Astrophysics Data System (ADS)

We analyze the optical response of WO3 sputtered thin films to NH3 gas sensing through transmittance changes. By sputtering, films with a combination of monoclinic and triclinic crystalline structure were obtained. The films show sensitivity to NH3 presence at the wavelengths ? = 980 nm and 1550 nm and at low temperature, T = 90 C. The optical constants (refractive index (n) and absorbant coefficient (?)) were calculated using the transmittance spectra and the model of a simple resonator. According to these results, an integrated optical NH3 sensor based on a glass waveguide with a WO3 thin film deposited at the surface was designed and experimentally characterized.

Lazcano-Hernndez, H. E.; Snchez-Prez, C.; Garca-Valenzuela, A.

2008-10-01

162

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

NASA Astrophysics Data System (ADS)

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

Andio, Mark A.

163

Measurement of Oil-Film Pressure in Engine Bearings Using a Thin-Film Sensor  

Microsoft Academic Search

In order to measure the oil-film pressure in engine bearings, the authors developed a new piezo-resistive thin-film pressure sensor. By physical vapor deposition, a sensor film of 3?6 micrometers thickness was deposited directly on to the engine plain bearing. This kind of sensor has been used to measure high pressure under elastohydrodynamic lubrication on the order of 1 GPa. However,

Yuji Mihara; Tsuneo Someya

2002-01-01

164

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

165

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

PubMed

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

Vergara, Alexander; Calavia, Raul; Vzquez, Rosa Mara; Mozalev, Alexander; Abdelghani, Adnane; Huerta, Ramn; Hines, Evor H; Llobet, Eduard

2012-09-01

166

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

167

Low energy consumption thick-film pressure sensors  

Microsoft Academic Search

This paper is focused on three different types of ceramic pressure sensors for the use in low-energy-consumption applications. We investigated the design issues for low energy consumption of sensing elements and compared the results and other sensors' characteristics for three different types of thick-film pressure sensors. The first type is the capacitive sensor, which is based on changes to the

D. Belavic; M. S. Zarnik; M. Mozek; S. Kocjan; M. Hrovat; J. Holc; M. Jerlah; S. Macek

2009-01-01

168

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

Microsoft Academic Search

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

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

2007-01-01

169

A Micro Gas Sensor Using TiO2 Nanotubes to Detect Volatile Organic Compounds  

NASA Astrophysics Data System (ADS)

To develop a portable gas sensor with low power consumption, we deposited a micro size sensing film (100100 m2) on a Si substrate with an integrated micro heater and electrodes constructed using micro-electro-mechanical system (MEMS) technology. TiO2 nanotubes ca. 500 nm long with a 50 nm diameter were used to sense and detect volatile organic compounds (VOCs). We demonstrate that the MEMS sensor responded well to ethanol and toluene in air at elevated temperatures, such as 500 C, which suggests that it is a promising battery-operable micro gas sensor for detecting VOCs.

Kida, Tetsuya; Seo, Min-Hyun; Suematsu, Koichi; Yuasa, Masayoshi; Kanmura, Yuichi; Shimanoe, Kengo

2013-04-01

170

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

PubMed

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

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

2014-03-15

171

Gas Permeation in Thin Glassy Polymer Films  

NASA Astrophysics Data System (ADS)

The development of asymmetric and composite membranes with very thin dense "skins" needed to achieve high gas fluxes enabled the commercial use of membranes for molecular level separations. It has been generally assumed that these thin skins, with thicknesses of the order of 100 nm, have the same permeation characteristics as films with thicknesses of 25 microns or more. Thick films are easily made in the laboratory and have been used extensively for measuring permeation characteristics to evaluate the potential of new polymers for membrane applications. There is now evidence that this assumption can be in very significant error, and use of thick film data to select membrane materials or predict performance should be done with caution. This presentation will summarize our work on preparing films of glassy polymers as thin as 20 nm and characterizing their behavior by gas permeation, ellipsometry and positron annihilation lifetime spectroscopy. Some of the most important polymers used commercially as gas separation membranes, i.e., Matrimid^ polyimide, polysulfone (PSF) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), have been made into well-defined thin films in our laboratories by spin casting techniques and their properties studied using the techniques we have developed. These thin films densify (or physically age) much faster than thicker films, and, as result, the permeability decreases, sometimes by several-fold over weeks or months for thin films. This means that the properties of these thin films can be very different from bulk films. The techniques, interpretations and implications of these observations will be discussed. In a broader sense, gas permeation measurements can be a powerful way of developing a better understanding of the effects of polymer chain confinement and/or surface mobility on the behavior of thin films.

Paul, Donald

2011-03-01

172

Self-assembled thin film chemical sensors  

SciTech Connect

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

Swanson, B.; Li, DeQuan

1996-11-01

173

Sensors and Actuators A 125 (2006) 170177 Thin film temperature sensor for real-time measurement  

E-print Network

Sensors and Actuators A 125 (2006) 170­177 Thin film temperature sensor for real-time measurement the conventional micro-thermocouples that have been reported. Additionally, use of micro-fabrication techniques.1016/j.sna.2005.05.021 #12;S. He et al. / Sensors and Actuators A 125 (2006) 170­177 171 placed

Mench, Matthew M.

174

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

175

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

176

Tellurium nano-structure based NO gas sensor.  

PubMed

Tellurium nanotubes were grown on bare and silver/gold nanoparticle (nucleation centers) deposited silicon substrates by vacuum deposition technique at a substrate temperature of 100 degrees C under high vacuum conditions. Silver and gold nanoparticles prepared on (111) oriented silicon substrates were found to act as nucleation centers for growth of Tellurium nanostructures. Density of nanotubes was found to increase while their diameter reduced when grown using metallic nanoparticle template. These Te nanostructures were investigated for their gas sensitivity. Tellurium nanotubes on Ag templates showed better response to NO in comparison to H2S and NH3 gases. Selectivity in response to NO was improved in comparison to Te thin film sensors reported earlier. The gas sensing mechanism was investigated using Raman and X-ray photoelectron spectroscopy techniques. The interaction of NO is seen to yield increased adsorption of oxygen that in turn increases hole density and conductivity in the material. PMID:19928213

Kumar, Vivek; Sen, Shashwati; Sharma, M; Muthe, K P; Jagannath; Gaur, N K; Gupta, S K

2009-09-01

177

Sensor array data profiling for gas identification.  

PubMed

The paper presents a new method of qualitative identification of gas. It is based on a dynamic response of sensor array with the emphasis on the processing of discrete measurement data. The information needed for identification of test samples is obtained in course of profiling the data from calibration measurements. This operation consists of the following steps: classification of data sets, selection of representative data sets, parameterization of classifiers associated with representative data sets and determination of data records. In our work Discriminant Function Analysis was used for data classification. The information saved in data record describes: the sequential number of discrete measurement, combination of gas sensors in this measurement which are best for classification of calibration samples, and the parameters of associated classifier. They are identifiers of gas class. The procedure of data record determination itself is time consuming. However this operation will be performed only at the stage of the development of the measurement instrument and when its malfunction is diagnosed. The routine use of the instrument will be restricted to gas identification task, which only utilizes the results of profiling. The identification of unknown gas is performed on the base of data records and measurement data obtained for this gas. Data records guide the preparation of data sets, separately for each class of gases. These data sets are used as input of the discriminant functions which have parameter values also indicated by data records. It was shown in the present contribution, that the qualitative identification of nine test gas samples (vapors of ethanol, acetic acid and ethyl acetate in air) with our method was very accurate and fast. PMID:19269438

Szczurek, A; Maciejewska, M; Ochromowicz, L

2009-05-15

178

A low-power micromachined MOSFET gas sensor  

Microsoft Academic Search

This paper reports on the design, fabrication, and characterization of the first low-power consumption MOSFET gas sensor, The novel MOSFET array gas sensor has been fabricated using anisotropic bulk silicon micromachining. A heating resistor, a diode used as temperature sensor, and four MOSFETs are located in a silicon island suspended by a dielectric membrane. The membrane has a low thermal

Danick Briand; Bart van der Schoot; Nicolaas F. de Rooij; Hans Sundgren; Ingemar Lundstrm

2000-01-01

179

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

180

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

Microsoft Academic Search

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

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

1998-01-01

181

Low power consumption thermal gas-flow sensor based on thermopiles of highly effective thermoelectric materials  

Microsoft Academic Search

A thermal gas-flow sensor based on thermopiles made of thin films of Bi0.87Sb0.13 for the n-type legs and Sb for the p-type legs with a high thermoelectric figure of merit is presented. The micromachined sensor chip is mounted within a package, which is kept at a constant temperature of 22C. Experimental data and the results of finite-element analysis calculations concerning

U Dillner; E Kessler; S Poser; V Baier; J Mller

1997-01-01

182

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

183

Understanding the response behavior of potentiometric gas sensors for non-equilibrium gas mixtures  

SciTech Connect

Many applications of gas sensors require concentration measurements of reactive gases in mixtures that are out of thermodynamic equilibrium. These applications include: hydrogen and hydrocarbon fuel gas sensors operating in ambient air for explosion hazard detection, carbon monoxide detection in ambient air for health protection, combustion efficiency sensors for stoichiometry control, and nitric oxide sensors for air pollution monitoring. Many potentiometric and amperometric electrochemical sensor technologies have been developed for these applications. A class of the potentiometric sensors developed for gas mixtures are the non-Nerstian sensors. This presentation defines a categorization and theoretical analysis of three distinct electrochemical processes that can produce a non-Nernstian sensor response.

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

2002-01-01

184

Review on optical fiber sensors with sensitive thin films  

NASA Astrophysics Data System (ADS)

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

Yang, Minghong; Dai, Jixiang

2012-03-01

185

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 1.132kHz under 10ppm 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

186

Temperature dependence of gas sensing behaviour of TiO{sub 2} doped PANI composite thin films  

SciTech Connect

In the present work we have reported the effect of temperature on the gas sensing properties of TiO{sub 2} doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and TiO{sub 2} doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline at low temperature. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature TiO{sub 2} doped PANI composite sensor shows higher response value and showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement.

Srivastava, Subodh, E-mail: subodhphy@gmail.com; Sharma, Preetam; Singh, M.; Vijay, Y. K. [Thin Film and Membrane Science Lab, Department of Physics, University of Rajasthan, Jaipur- 302004 (India); Sharma, S. S. [Department of Physics, Govt. Women Engineering College, Ajmer-305002 (India); Sharma, Vinay; Rajura, Rajveer Singh [Centre for Converging Technology, University of Rajasthan, Jaipur-302004 (India)

2014-04-24

187

CBD grown ZnO-based gas sensors and dye-sensitized solar cells  

Microsoft Academic Search

Chemical bath deposition (CBD) is used for depositing different metal chalcogenide and oxide thin films through an ion-by-ion or by adsorption of colloidal particles from the solution on the substrate. In this review, we focused our intension on CBD zinc oxide (ZnO) films synthesis with different proposed deposition mechanisms and their integration into gas sensor and dye-sensitized solar cells. Due

C. D. Lokhande; P. M. Gondkar; Rajaram. S. Mane; V. R. Shinde; Sung-Hwan Han

2009-01-01

188

Compact portable QEPAS multi-gas sensor  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

189

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

190

Fabrication of nanoporous and hetero structure thin film via a layer-by-layer self assembly method for a gas sensor  

Microsoft Academic Search

Nanoporous and hetero structure thin film consisted of weak polyelectrolytes and TiO2 nanoparticles was fabricated by the sequential depositions of oppositely charged solutions via a layer-by-layer self assembly (LBL-SA) method on a quartz crystal microbalance (QCM) at room temperature and then by an immersion in acidic water (pH 1.8) for 2min and neutral water for 10s subsequently. Because in this

Jin Ho Kim; Sae Hoon Kim; Seimei Shiratori

2004-01-01

191

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 500C. This study reports various approaches to detect NO and NO2 selectively under lean and humid conditions at temperatures from 300C to 800C. 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 550C and 600C, 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 600C and 800C. 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.; Yce, A.; Gnll, Y.

2012-06-01

192

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

193

"Metal-oxide gas sensors have been around for  

E-print Network

Publishing "Metal-oxide gas sensors have been around for over 40 years, but only now we have: Surface Studies of Gas Sensing Metal Oxides 21 February 2007 1. Could you explain the significance of your article to the non-specialist? Metal oxide-gas sensors are practical devices used in a variety of every

Diebold, Ulrike

194

Development of a detection sensor for lethal H2S gas.  

PubMed

The gas which may be lethal to human body with short-term exposure in common industrial fields or workplaces in LAB may paralyze the olfactory sense and impose severe damages to central nervous system and lung. This study is concerned with the gas sensor which allows individuals to avoid the toxic gas that may be generated in the space with residues of organic wastes under 50 degrees C or above. This study investigates response and selectivity of the sensor to hydrogen sulfide gas with operating temperatures and catalysts. The thick-film semiconductor sensor for hydrogen sulfide gas detection was fabricated WO3/SnO2 prepared by sol-gel and precipitation methods. The nanosized SnO2 powder mixed with the various metal oxides (WO3, TiO2, and ZnO) and doped with transition metals (Au, Ru, Pd Ag and In). Particle sizes, specific surface areas and phases of sensor materials were investigated by SEM, BET and XRD analyses. The metal-WO3/SnO2 thick films were prepared by screen-printing method. The measured response to hydrogen sulfide gas is defined as the ratio (Ra/R,) of the resistance of WO3ISnO2 film in air to the resistance of WO3/SnO2 film in a hydrogen sulfide gas. It was shown that the highest response and selectivity of the sensor for hydrogen sulfide by doping with 1 wt% Ru and 10 wt% WO3 to SnO2 at the optimum operating temperature of 200 degrees C. PMID:22966558

Park, Young-Ho; Kim, Yong-Jae; Lee, Chang-Seop

2012-07-01

195

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

196

Ferroelectric thin-film active sensors for structural health monitoring  

NASA Astrophysics Data System (ADS)

Piezoelectric wafer active sensors (PWAS) have been proven a valuable tool in structural health monitoring. Piezoelectric wafer active sensors are able to send and receive guided Lamb/Rayleigh waves that scan the structure and detect the presence of incipient cracks and structural damage. In-situ thin-film active sensor deposition can eliminate the bonding layer to improve the durability issue and reduce the acoustic impedance mismatch. Ferroelectric thin films have been shown to have piezoelectric properties that are close to those of single-crystal ferroelectrics but the fabrication of ferroelectric thin films on structural materials (steel, aluminum, titanium, etc.) has not been yet attempted. In this work, in-situ fabrication method of piezoelectric thin-film active sensors arrays was developed using the nano technology approach. Specification for the piezoelectric thin-film active sensors arrays was based on electro-mechanical-acoustical model. Ferroelectric BaTiO3 (BTO) thin films were successfully deposited on Ni tapes by pulsed laser deposition under the optimal synthesis conditions. Microstructural studies by X-ray diffractometer and transmission electron microscopy reveal that the as-grown BTO thin films have the nanopillar structures with an average size of approximately 80 nm in diameter and the good interface structures with no inter-diffusion or reaction. The dielectric and ferroelectric property measurements exhibit that the BTO films have a relatively large dielectric constant, a small dielectric loss, and an extremely large piezoelectric response with a symmetric hysteresis loop. The research objective is to develop the fabrication and optimum design of thin-film active sensor arrays for structural health monitoring applications. The short wavelengths of the micro phased arrays will permit the phased-array imaging of smaller parts and smaller damage than is currently not possible with existing technology.

Lin, Bin; Giurgiutiu, Victor; Yuan, Zheng; Liu, Jian; Chen, Chonglin; Jiang, Jiechao; Bhalla, Amar S.; Guo, Ruyan

2007-04-01

197

Development of carbon nanotube-based gas sensors for NO x gas detection working at low temperature  

NASA Astrophysics Data System (ADS)

Carbon nanotube (CNT)-based NO x gas sensors which can operate at room temperature were prepared on Al 2O 3 substrates with interdigitated Pt-electrodes using both dc sputtering method and chemical vapor deposition (CVD) method. In this method, Al buffer layer and Fe catalytic thin film were prepared on the substrate by dc sputtering method and then CNTs were grown by thermal CVD method using ethylene gas. The scanning electron microscope (SEM) images of the CNTs on the substrates indicated that the vertically aligned multi-walled CNT (MWCNT) and the randomly oriented MWCNT were grown selectively by insertion of Al buffer layer. Gas sensing property to NO and NO 2 gases were measured. Resistance of the prepared CNT-based gas sensor decreased with increase of NO and NO 2 gas concentration. UV light irradiation was examined to detach the adsorbed gas molecule at room temperature. In this paper, it is suggested that CNT-based gas sensors have a great possibility to apply innovative NO x gas sensor from the experimental result.

Ueda, T.; Bhuiyan, M. M. H.; Norimatsu, H.; Katsuki, S.; Ikegami, T.; Mitsugi, F.

2008-05-01

198

Highly selective ethanol In 2O 3-based gas sensor  

Microsoft Academic Search

The sensitive composite material was prepared by loading Pt and La2O3 into ultrafine In2O3 matric material (8nm) synthesized by microemulsion method. A highly selective ethanol gas sensor was developed based on hot-wire type gas sensor, which was sintered in a bead (0.8mm in diameter) to cover a platinum wire coil (0.4mm in diameter). The gas sensor was operated by a

Zili Zhan; Jianwei Lu; Wenhui Song; Denggao Jiang; Jiaqiang Xu

2007-01-01

199

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

200

Graphene/mica based ammonia gas sensors  

NASA Astrophysics Data System (ADS)

In this paper, graphene/mica and graphene/SiO2 based ammonia gas sensors are compared. It is found that adsorbed NH3 molecules result in up-shifting of the Fermi level in graphene, leading to a significant increase in graphene resistance. In comparison with SiO2 supporting substrate, the mica supporting substrate is found to induce more p-doping in graphene, in favour of NH3 molecule adsorption, yielding a high sensitivity. These findings suggest that the substrate plays an important role in mediating the interaction between graphene and NH3 molecules and that mica can be an excellent underlying substrate for graphene for ammonia gas detection.

Ben Aziza, Zeineb; Zhang, Qing; Baillargeat, Dominique

2014-12-01

201

A low-power CMOS compatible integrated gas sensor using maskless tin oxide sputtering  

Microsoft Academic Search

This paper describes a CMOS compatible integrated gas sensor. The device was designed so that the front-end fabrication is fully compatible with the standard CMOS process. The non-CMOS compatible fabrication steps were carried out as post-processing steps. This included the silicon anisotropic etch to create the thermally isolated micro-hotplate (MHP) and the deposition of gas-sensitive thin films using maskless r.f.

Lie-yi Sheng; Zhenan Tang; Jian Wu; Philip C. H. Chan; Johnny K. O. Sin

1998-01-01

202

Percolating SnO 2 nanowire network as a stable gas sensor: Direct comparison of long-term performance versus SnO 2 nanoparticle films  

Microsoft Academic Search

A comparative study of the long-term gas-sensing performance of chemiresistors made of: (i) mats of randomly oriented single crystal SnO2 nanowires and (ii) thin layers of pristine SnO2 nanoparticles, has been carried out. The sensing elements made of percolating nanowires demonstrate excellent sensitivity and long-term stability toward traces of 2-propanol in air. Different from the nanowire network, the superior initial

V. V. Sysoev; T. Schneider; J. Goschnick; I. Kiselev; W. Habicht; H. Hahn; E. Strelcov; A. Kolmakov

2009-01-01

203

Detecting Changes of a Distant Gas Source with an Array of MOX Gas Sensors  

PubMed Central

We address the problem of detecting changes in the activity of a distant gas source from the response of an array of metal oxide (MOX) gas sensors deployed in an open sampling system. The main challenge is the turbulent nature of gas dispersion and the response dynamics of the sensors. We propose a change point detection approach and evaluate it on individual gas sensors in an experimental setup where a gas source changes in intensity, compound, or mixture ratio. We also introduce an efficient sensor selection algorithm and evaluate the change point detection approach with the selected sensor array subsets. PMID:23443385

Pashami, Sepideh; Lilienthal, Achim J.; Trincavelli, Marco

2012-01-01

204

Parametric Study of Gas Turbine Film-Cooling  

E-print Network

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. The study consisted of three parts: 1) turbine blade span film...

Liu, Kevin

2012-10-19

205

Nanostructured semiconductor gas sensors to overcome sensitivity limitations due to percolation effects  

NASA Astrophysics Data System (ADS)

Semiconductor gas sensors are widespread in applications to detect toxic or explosive gases. Their gas-sensitive layer consists of a polycrystalline metal oxide film. The gas-detection principle is based on variations of the depletion layer at the grain boundaries in presence of reducing or oxidizing gases which leads to variations in the height of the energy barriers for free charge carriers (e.g. electrons in case of SnO 2). The presence of a gas reduces the height of these barriers thus leading to an increased conductivity of the sensing material. The lower detection limit for gases is given by the fact that no (at least single) connected path exists between the reading electrodes below a certain gas concentration. The sensitivity of a gas sensor as well as its dynamic range can be improved significantly when nano technology methods are used to allow for parallel reading of shorter paths.

Blser, G.; Rhl, Th.; Diehl, C.; Ulrich, M.; Kohl, D.

206

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

207

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

Malag, Cesare; Fabbri, Barbara; Gherardi, Sandro; Giberti, Alessio; Guidi, Vincenzo; Landini, Nicol; Zonta, Giulia

2014-01-01

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

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

2014-01-01

210

Stagnation temperature measurement using thin-film platinum resistance sensors  

NASA Astrophysics Data System (ADS)

The measurement of stagnation temperature in high-speed flows is an important aspect of gas turbine engine testing. The ongoing requirement to improve the accuracy of such measurements has led to the development of probe systems that use a thin-film platinum resistance thermometer (PRT) as the sensing element. For certain aspects of engine testing this type of sensing device potentially offers superior measurement performance to the thermocouple, the temperature sensor of choice in most gas turbine applications. This paper considers the measurement performance of prototype PRT-based stagnation temperature probes, up to high-subsonic flow conditions, using passively aspirated probe heads. The relatively poor temperature recovery performance of a simply constructed probe has led to the development of a new design that is intended to reduce the impact of thermal conduction within the probe assembly. The performance of this so-called dual-skin probe has been measured through a series of tests at a range of Mach numbers, incidence angles and Reynolds numbers. The data reveal that a high probe recovery factor has been achieved with this device, and that the application of this design to engine tests would yield the measurement performance benefits of the PRT whilst requiring small levels of temperature recovery compensation.

Bonham, C.; Thorpe, S. J.; Erlund, M. N.; Stevenson, R. D.

2014-01-01

211

Gas sensing properties of epitaxial SnO 2 thin films prepared by atomic layer deposition  

Microsoft Academic Search

Undoped SnO2 thin films are grown on ?-Al2O3(012) (r-cut sapphire) substrates by gas phase atomic layer deposition (ALD). Two precursor pairs, SnI4O2 and SnCl4H2O2, both new for ALD, are used. The films have a cassiterite structure and are (101)[010]cassiterite||(012)[100]sapphire oriented. A good epitaxial quality and the conductivity acceptable from the standpoint of semiconductor gas sensors are achieved for ultrathin films

A. Rosental; A. Tarre; A. Gerst; J. Sundqvist; A. Hrsta; A. Aidla; J. Aarik; V. Sammelselg; T. Uustare

2003-01-01

212

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

NASA Astrophysics Data System (ADS)

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 ?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 ?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

2012-09-01

213

Novel millimeter-wave gas sensor using dielectric resonator with sensitive layer on TiO2  

Microsoft Academic Search

A new generation of gas sensors that operates in millimeter-wave frequency range is presented. The sensor uses a dielectric resonator operating with whispering-gallery modes. Here the dielectric resonator is covered by TiO2 thin film as sensitive layer. A gas or humidity adsorption makes the TiO2 dielectric permittivity changing and such changing modifies the resonant frequencies of high-Q whispering-gallery modes within

H. Hallil; P. Menini; H. Aubert

2009-01-01

214

Low-level detection of ethanol and H 2S with temperature-modulated WO 3 nanoparticle gas sensors  

Microsoft Academic Search

Low-level detection of ethanol and H2S was achieved with thermally modulated WO3 nanoparticle gas sensors. Nanoparticle WO3 films, with a mean grain size of ?5nm and a thickness of ?20?m, were produced by advanced reactive gas evaporation onto alumina substrates. The working temperature of the sensor was periodically modulated between 150 and 250C, and the response was analysed by fast

R. Ionescu; A. Hoel; C. G. Granqvist; E. Llobet; P. Heszler

2005-01-01

215

Detection of Smoldering Fire Using Tin Oxide Gas Sensors  

Microsoft Academic Search

Detecting technique of smoldering fire was examined using tin oxide gas sensors. Eight sensors were installed in a room. They were same type. Four kinds of materials were adopted as a fire-source material. The materials were cotton cloth, wallpaper, curtain cloth and woodchip, which were main smoldering fire-source materials in an indoor environment. The sensor outputs to gases evolved upon

Tsubasa Higashino; Ayako Sawada; Takashi Oyabu; Yoshinori Takei; Hidehito Nanto; Kiyoshi Toko

2007-01-01

216

Nanostructured Tin Dioxide Materials for Gas Sensor Applications  

E-print Network

in comparison to other gas sensing methods. Semiconduc- tor sensors are inexpensive to produce, easy temperatures. Semiconductor sensors can be produced in arrays to allow sensing of mul- tiple species to the low operating temperatures, high sen- sitivities, mechanical simplicity of sensor design and low

Wooldridge, Margaret S.

217

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

218

Artificial neural networks and gas sensor arrays: quantification of individual components in a gas mixture  

Microsoft Academic Search

A very promising way of increasing the selectivity and sensitivity of gas sensors is to treat the signals from a number of different gas sensors with pattern recognition (PARC) methods. A gas sensor array with six metal-oxide-semiconductor field-effect-transistors (MOSFETs) operating at elevated temperatures was exposed to two types of multiple-component gas mixture, one containing 5-65 ppm of hydrogen, ammonia, ethanol

H. Sundgren; F. Winquist; I. Lukkari; I. Lundstrom

1991-01-01

219

CMOS Interfacing for Integrated Gas Sensors: A Review  

Microsoft Academic Search

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

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

2010-01-01

220

Application of dielectrophoresis to fabrication of carbon nanohorn gas sensor  

Microsoft Academic Search

This paper describes an electrokinetic fabrication method for a gas sensor composed of single-wall carbon nanohorns (SWCNHs) using dielectrophoresis (DEP). The authors have previously demonstrated that DEP manipulation of carbon nanotubes (CNTs) can be applied to the fabrication of a CNT gas sensor. In the present study, we further explored the possibility of electrokinetic manipulation of SWCNHs. The latter have

Junya Suehiro; Noriaki Sano; Guangbin Zhou; Hiroshi Imakiire; Kiminobu Imasaka; Masanori Hara

2006-01-01

221

Study of ionic liquid immobilization on polyvinyl ferrocene substrates for gas sensor arrays.  

PubMed

In this report, the effects of conductive polymer oxidation states and structures on the design and development of ionic liquid (IL)/conductive polymer (CP) composite films for gas sensing are systematically characterized. Four different polyvinyl ferrocene (PVF) films synthesized by varying the conditioning potential (0.7 vs 0.0 V) and the electrolyte are tested for their gas-sensing properties (e.g., sensitivity, selectivity, response time, linearity, and dynamic range against various gas analytes such as dichloromethane, ethanol, natural gas, methane, formaldehyde (37%), and benzene) utilizing the quartz crystal microbalance (QCM) and ATR-FT-IR. The best available film is further studied as a substrate for the immobilization of various ILs that enhanced both the sensitivity and selectivity. Finally, two arrays, each comprising four sensors with the following scheme are developed and characterized for their ability to classify the four target analytes by using linear discriminant analysis: (1) the highest sensitivity PVF film immobilized with four different ILs and (2) the highest sensitivity IL immobilized in four different PVF films. Array 2 is proven to be much better than array 1 in discriminating the analytes, which is very significant in establishing the fact that a diverse set of PVF redox states allow the rational development of a PVF/IL composite-based sensor array in order to analyze complex mixtures utilizing structural differences and the extent of intermolecular interactions. PMID:21410206

Hou, Kuang-Yu; Rehman, Abdul; Zeng, Xiangqun

2011-04-19

222

Space Shuttle main engine hot gas temperature sensor  

Microsoft Academic Search

The Space Shuttle Main Engine (SSME) is a liquid oxygen-fueled rocket engine. Hot gas sensors are mounted in the turbine discharge-to-main combustion chamber duct. During the sequence, prior to ignition of the solid booster rockets, the engine mounted computer will inhibit a launch if the hot gas sensors outputs are not within limits. The sensors also serve to monitor the

D. Myhre

1982-01-01

223

A Smart Gas Sensor Insensitive to Humidity and Temperature Variations  

NASA Astrophysics Data System (ADS)

The accuracy of the quantitative sensing of volatile organic compounds by chemoresistive gas sensors suffers from the fluctuations in the background atmospheric conditions. This is caused by the drift-like terms introduced in the responses by these instabilities, which should be identified and compensated. Here, a mathematical model is presented for a specific chemoresistive gas sensor, which facilitates these identification and compensation processes. The resistive gas sensor was considered as a multi-input-single-output system. Along with the steady state value of the measured sensor resistance, the ambient humidity and temperature are the inputs to the system, while the concentration level of the target gas is the output. The parameters of the model were calculated based on the experimental database. The model was simulated by the utilization of an artificial neural network. This was connected to the sensor and could deliver the correct contamination level upon receiving the measured gas response, ambient humidity and temperature.

Hajmirzaheydarali, Mohammadreza; Ghafarinia, Vahid

2011-02-01

224

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

...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

225

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

226

Sensitivity enhancement of nanostructured SnO2 gas sensors fabricated using the glancing angle deposition method.  

PubMed

0.5 wt.% Pd-catalyzed SnO2 thin-film gas sensors with microstructures controlled on a nanometer scale were fabricated by an e-beam evaporator using the glancing angle deposition (GAD) method. After annealing at 500 degrees C for 1 h, the sensors produced were polycrystalline with a nanoporous, tilted columnar microstructure. The gas-sensing properties of these SnO2 sensors were measured in the concentration range of 1 to 5 ppm NO2 at 250 degrees C and of 10 to 50 ppm C2H5OH at 400 degrees C, respectively. The sensors fabricated by e-beam evaporation in combination with the GAD method showed much higher sensitivities than normally prepared sensors and exhibited rapid response times. The gas sensitivity (S = R(gas)/R(air)) of the SnO2 sensor using the GAD method was 43.4 for 5 ppm NO2 and 0.08 for 10 ppm C2H5OH, respectively. These sensors showed excellent sensitivities compared to the normal thin film sensors (S = 2 for 5 ppm NO2 and 0.92 for 10 ppm C2H5OH). We consider that the nanostructured sensors produced using the GAD process could be used to detect various gases emitted by automobiles and industrial installations. PMID:23763153

Gwon, Hyo Jin; Moon, Hi Gyu; Jang, Ho Won; Yoon, Seok-Jin; Yoo, Kwang Soo

2013-04-01

227

Sensors and Actuators A 116 (2004) 369377 Demonstration and characterization of PZT thin-film sensors and  

E-print Network

-film sensors and actuators for meso- and micro-structures Yi-Chu Hsua, Chia-Che Wub, Cheng-Chun Leeb, G.Z. CaocSensors and Actuators A 116 (2004) 369­377 Demonstration and characterization of PZT thin, such as endoscopes and hearing aids, call for PZT (lead zirconate titanate oxide) thin-film sensors and actuators

Cao, Guozhong

228

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

229

Biochemical sensors based on thin-film waveguide  

Microsoft Academic Search

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

Haruyuki MINAMITANI; Kyungho KIM; Kunihiro MATSUMOTO

1998-01-01

230

Nano-diamond film pressure sensor  

Microsoft Academic Search

The edges and corners of nanocrystalline diamond were natural field-emitters. Nano-graphite was mixed in nanocrystalline diamond and cellulose or other organic vehicles to fabricate paste for screen-printed film. The aim of mixed nano-graphite to enhance electric conduction of Nano-diamond film. Through enough ultrasonic disperse the nano-diamond, the paste was screen-printed on the substrates to form Nano- diamond film (NDF). The

Xiuxia Zhang; Wei Shuyi; Erlei Wang; Lixia Zhang; Bingheng Lu

2011-01-01

231

Surface acoustic wave humidity sensor using polyvinyl-alcohol film  

Microsoft Academic Search

A surface acoustic wave (SAW) sensor has been fabricated and used to study the hygroscopic properties of the polyvinyl-alcohol (PVA) polymer film as layer chemically sensitive to relative humidity (RH). A 42 MHz SAW device has been configured as delay line onto 128 YX-LiNbO3 substrate with the SAW path totally covered by the spin-coated PVA film. The SAW phase response

M. Penza; V. I. Anisimkin

1999-01-01

232

INTERFACIAL STABILITY OF THIN FILM FIBER-OPTIC HYDROGEN SENSORS  

E-print Network

/CP-610-32405 #12;Introduction Public perception of the hazards of hydrogen fuel use, its production time: reaction of thin films with hydrogen gas results in an optical change that can be sensed by a probe beam

233

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

234

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

235

Radiation effects in tin dioxide as gas sensors  

Microsoft Academic Search

The radiation effects in the process of preparation of SnO2 materials by a sol-gel method from Sn(OC2H5)4 and on gas sensors of SnO2 have been investigated including relationships between gelling time and vicosity of the products hydrolyzed and the irradiated doses from 50 to 500 kGy, sensitivity of the gas sensors to ethanol gas etc., and their electrical characteristics. The

Zhang Jian-Cheng; Shen Jia-Qi; Shan Zhao-Jon; Zhou Shu-Xin; Zhu Jin-Laing

1994-01-01

236

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

237

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

2014-01-01

238

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

NASA Technical Reports Server (NTRS)

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

Hopson, Jr., Purnell (Inventor)

1996-01-01

239

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

2014-01-01

240

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.

241

Estimation of Gas-Source Location Using Gas Sensors and Ultrasonic Anemometer  

Microsoft Academic Search

This paper reports on a new method to search for a gas source. In the previous works on gas-source localization, robotic or human searchers were navigated using gas sensors and anemometers in order to track gas plumes and find their source locations. Instead, the proposed method provides a map showing the certainty of the gas-source location. In the proposed method,

T. Ushiku; N. Satoh; H. Ishida; S. Toyama

2006-01-01

242

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

243

Ionization-based gas sensor using aligned MWCNTs array  

Microsoft Academic Search

Current gas sensors are mainly categorized into two modes of operation; chemical type operating by gas adsorption and physical type using ionization method. Chemical type conductivity-based gas detectors are large in size, they operate at high temperatures, and their response time is slow. Moreover most of them are only capable of detecting single type gases due to their low selectivity.

A. R. Kermany; N. M. Mohamed; B. S. Mahinder Singh

2010-01-01

244

Industrialisation of Gas Sensors for Comfort, Security and Wellness  

Microsoft Academic Search

Variations in the design of gas sensing Microsystems yield a wide variety of device characteristics that can be exploited to fulfill heterogeneous application requirements. For successful industrialization, of a gas sensing application, care has to be taken in advance, that the chosen sensing technology has the potential to fulfill all needs of the intended application. Gas sensors based on the

Maximilian Fleischer

2007-01-01

245

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

246

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

247

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

248

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

NASA Astrophysics Data System (ADS)

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

2014-09-01

249

Metal oxide gas sensors upon various temperature-induced profiles  

NASA Astrophysics Data System (ADS)

This paper presents how an array of sensors with different sensitivities to gases can be applied for detection of hydrogen in the presence of humidity when operated upon various temperature - induced profiles. The sensors in the array are subject to temperature modulation over the range of 350 - 500C. Temperature profiles are based on a cardinal sine as well as Meyer wavelet phi and psi functions. Changes in the sensor operating temperature lead to distinct resistance patterns of the sensors depending on gas concentration. The sensors responses are studied as a function of target gas concentration (0 - 3000 ppm) and relative humidity level (0 - 75%Rh). Feedforward back-propagation neural networks are used in order to facilitate gas concentration and humidity level prediction. The results show reliable hydrogen detection upon temperature modulation and a reduction of the total power consumption.

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

2014-08-01

250

Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing  

PubMed Central

In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method. PMID:22163623

Wongchoosuk, Chatchawal; Wisitsoraat, Anurat; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Kerdcharoen, Teerakiat

2010-01-01

251

A Tunable Gas Sensor Using an Acoustic Waveguide  

NASA Astrophysics Data System (ADS)

A tunable gas sensor using surface acoustic waves (SAW) is described. It is designed on the basis of a waveguide delay line fabricated on a piezoelectric substrate made of 128 Y-cut LiNbO3. A voltage applied between the waveguide and two electrodes causes a local change in the properties of the substrate near the waveguide and differently affects the sensors response to the vapors of various analytes. Some results of the experimental study of the sensor, which show the change in the selectivity under the effect of voltage, are presented. The analytes used for testing include a number of alcohols and deionized water. The possibilities for employing such a sensor in the sensor arrays of gas analyzers of the electronic nose type are discussed.

Gulyaev, Yu. V.; Zemlyakov, V. E.; Kryshtal', R. G.; Medved', A. V.; van Fong, Khoang; Shemet, V. V.

2001-01-01

252

A tunable gas sensor using an acoustic waveguide  

Microsoft Academic Search

A tunable gas sensor using surface acoustic waves (SAW) is described. It is designed on the basis of a waveguide delay line\\u000a fabricated on a piezoelectric substrate made of 128 Y-cut LiNbO3. A voltage applied between the waveguide and two electrodes causes a local change in the properties of the substrate near\\u000a the waveguide and differently affects the sensors response

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

2001-01-01

253

Development of titania heated exhaust-gas oxygen sensor  

Microsoft Academic Search

In this system, the composition of the engine exhaust gas must be maintained in a narrow range around the stoichiometry point to achieve high conversion efficiency for the catalyst. The closed-loop feedback control system using an oxygen sensor has been developed for this purpose. Two types of oxygen sensors have been developed: the potentiometric type using zirconia (ZrO) ceramic electrolyte

Takami

1988-01-01

254

Perovskite oxides for semiconductor-based gas sensors  

Microsoft Academic Search

The oxygen partial pressure dependence of the point defect concentration, and thus conductivity, in oxide semiconductors allows for their use in high-temperature gas sensors. In addition to responding to oxygen partial pressure, the resistance of oxide semiconductors can be affected by other gases, such as carbon monoxide, hydrocarbons and ethanol, which creates opportunities for developing new sensors, but also leads

Jeffrey W. Fergus

2007-01-01

255

A NEW LED-LED PORTABLE CO2 GAS SENSOR BASED ON AN INTERCHANGEABLE MEMBRANE SYSTEM FOR INDUSTRIAL APPLICATIONS  

E-print Network

. Carbon dioxide sensor; Gas sensor; Optical sensor; Paired emitter detector-diode sensor; Portable, cheese, etc.), beverages, refrigeration systems, welding systems, fire extinguishers, water treatment

Lee, Hyowon

256

Novel gas sensors based on carbon nanotube networks  

NASA Astrophysics Data System (ADS)

Novel resistive gas sensors based on single-walled carbon nanotube (SWNT) networks as the active sensing element nave been investigated for gas detection. SWNTs networks were fabricated by airbrushing on alumina substrates. As-produced- and Pd-decorated SWNT materials were used as sensitive layers for the detection of NO2 and H2, respectively. The studied sensors provided good response to NO2 and H2 as well as excellent selectivities to interfering gases.

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

2008-08-01

257

Modeling of Infrared Gas Sensors Using a Ray Tracing Approach  

Microsoft Academic Search

Many gas molecules absorb electromagnetic radiation at characteristic wavelengths in the infrared region. This absorption can be used to identify defined substances like CO2, ammoniac, and so forth. A lot of different types of gas sensors are based on the principle of infrared absorption like photoacoustic sensors (e.g., Golay cells), dispersive infrared instruments (e.g., utilizing a diffraction grating), or Fourier

Johann Mayrwger; Peter Hauer; Wolfgang Reichl; Reinhard Schwdiauer; Christian Krutzler; Bernhard Jakoby

2010-01-01

258

Laterally grown ZnO nanowire ethanol gas sensors  

Microsoft Academic Search

We report the growth of ZnO nanowires on ZnO:Ga\\/glass templates and the fabrication of laterally grown ZnO nanowire ethanol sensors. It was found that growth direction of the nanowires depends strongly on growth parameters. It was also found that resistivity of the fabricated sensor decreased upon ethanol gas injection. By introducing 1500ppm ethanol gas, it was found that the device

Ting-Jen Hsueh; Cheng-Liang Hsu; Shoou-Jinn Chang; I-Cherng Chen

2007-01-01

259

Selective mixed potential ammonia exhaust gas sensor  

Microsoft Academic Search

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

Daniela Schnauer; Kerstin Wiesner; Maximilian Fleischer; Ralf Moos

2009-01-01

260

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

261

The influence of precursor powders and processing parameters on the properties of SnO 2 -based gas sensors  

Microsoft Academic Search

Semiconducting tin oxide precursor powders were synthesized via three different chemical processing routes. The influence of powder processing conditions on the physical properties, e.g., particle size, surface area and phase composition of both uncalcined and calcined materials, was investigated. These powders were used to fabricate gas sensors using thick-film screen-printing technology. The effect of precursor powders, sintering conditions, sensor temperature

A. Ahmad; J. Walsh

2003-01-01

262

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

263

Reflectance Infrared Spectroscopy on Operating Surface Acoustic Wave Chemical Sensors During Exposure to Gas-Phase Analytes  

SciTech Connect

We have developed instrumentation to enable the combination of surface acoustic wave (SAW) sensor measurements with direct, in-situ molecular spectroscopic measurements to understand the response of the SAW sensors with respect to the interfacial chemistry of surface-confined sensing films interacting with gas-phase analytes. Specifically, the instrumentation and software was developed to perform in-situ Fourier-transform infrared external-reflectance spectroscopy (FTIR-ERS) on operating SAW devices during dosing of their chemically modified surfaces with analytes. By probing the surface with IR spectroscopy during gas exposure, it is possible to understand in unprecedented detail the interaction processes between the sorptive SAW coatings and the gaseous analyte molecules. In this report, we provide details of this measurement system, and also demonstrate the utility of these combined measurements by characterizing the SAW and FTIR-ERS responses of organic thin-film sensor coatings interacting with gas-phase analytes.

Hierlemann, A.; Hill, M.; Ricco, A.J.; Staton, A.W.; Thomas, R.C.

1999-01-11

264

Use of conducting polypyrrole blends as gas sensors  

Microsoft Academic Search

We discuss the use of polymeric blends formed by the controlled growth of doped polypyrrole chains in the interior of films of different dielectric polymers as sensors of the presence of representative examples of volatile organic compounds. The dielectric films (of either (poly(caprolactone), poly(ethylene oxide), poly(methyl-methacrylate), poly(vinyl alcohol), or poly(vinyl-acetate)) containing an appropriate oxidizing agent were prepared atop a conducting

C. P. de Melo; B. B. Neto; E. G. de Lima; L. F. B. de Lira; J. E. G. de Souza

2005-01-01

265

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

266

Portable mid-infrared gas sensors: Development and applications  

NASA Astrophysics Data System (ADS)

Several novel compact architectures of diode laser based absorption gas sensors have been developed, characterized and applied to real world applications. The motivation for this research has been the need to develop highly sensitive, selective and rapid response gas sensors that operate reliably in a non-laboratory environment. The gas sensors utilize rare earth doped fiber amplified near infrared diode lasers and are difference frequency mixed in periodically poled LiNbO3 to generate narrow linewidth ?W to mW-level mid infrared light in the molecular fingerprint region from 3 to 5 ?m. In particular, the spectroscopic performance of an automated widely tunable (3.3-4.4 ?m) multi-species and a high-power single species (3.5 ?m) gas detection sensor are discussed. Sensitive, selective and real-time detection of over 10 gas species including CH4, H2CO, CO2, CH 3OH, NO2, N2O; SO2, HCl, C6H 6, and H2O using extractive gas sampling in a multi- pass cell was demonstrated. The gas sensors were used for an evaluation of a trace contaminant catalyst system at TDA Research, Wheat Ridge, Colorado, and successfully applied to the detection of volcanic gases at Masaya volcano, Nicaragua.

Richter, Dirk

267

Aerosol synthesis of chemoresistive gas sensors: Materials, structures and performances  

Microsoft Academic Search

The sensing performance of nanoparticle films obtained by aerosol synthesis is investigated as a function of material composition (e.g. SnO2, TiO2, WO3), film morphology and layout. It is shown that highly porous (98%) films are obtained by direct deposition from the gas phase. Utilization of a flame spray pyrolysis (FSP) reactor as particle source was found to be a flexible

Antonio Tricoli; Marco Righettoni; Sotiris E. Pratsinis

2010-01-01

268

Elastic plate mode sensitivities to mass loading applications to gas sensors  

NASA Astrophysics Data System (ADS)

The theoretical analysis of the possibility of measuring mass loading variations by means of bulk wave modes generated with Interdigital Transducers (IDT) is addressed. Elastic waves are generated and detected by means of IDT transducers plated on piezoelectric fields or substrates. It was shown that both surface and bulk elastic waves can be launched by IDT's. The type of elastic wave excited is related to the piezoelectric material properties and its crystallographic orientation. In a thin piezoelectric plate, surface and bulk vibrations propagate in the volume of the plate. Thus, propagating plate modes are stationary in the plate thickness. Two kinds of modes can be distinguished: Shear Horizontal (SH) and Lamb modes. To adapt a plate mode device to a gas sensor, it is necessary to deposit a selectivity sensitive film which can absorb the gas to be detected. The velocity of the wave is then modified because the induced variation of the mass loading of the film changes the boundary conditions. The theoretical study of the mass loading sensitity of both SH and Lamb modes is presented. For instance, expected sensitivity for the SH mode of a gas sensor is in the order of 1 ng of the gas for 1 sq cm of sensitive film.

Hoummady, M.; Hauden, D.

1992-06-01

269

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

270

40 Platinum-porous SiC gas sensor: Investigation sensing properties of H2 gas  

NASA Astrophysics Data System (ADS)

The present paper reports on a new structure for H2 gas sensing based on thin porous silicon carbide (PSiC) films. The PSiC layer has been formed by electrochemical etching of SiC films previously deposited onto p-type silicon substrate by pulsed laser deposition (PLD) using 6H-SiC target. Current-voltage (I-V) and current-time (I-t) characteristics have been measured. A thin platinum (Pt) film (40 thickness) deposited onto PSiC layer has been used as a catalytic metal. The Schottky diode parameters such as ideality factor (n), barrier height (?Bp) and series resistance (RS) have been evaluated under different concentrations of H2 gas. The experimental results show that upon exposure to H2 gas the barrier height, the ideality factor and the series resistance change significantly. The different changes in the electrical parameters of the structure (increase and decrease as a function of the H2 concentration) have been explained by the formation of two inversion layers. The first one forms as soon as the gas is in contact with the sensor and the second when the concentration reaches 90 ppm. Subsequently, the effect of gas concentration on the maximum sensitivity value of the sensor has been investigated. A high sensitivity (?I/I) value around 86% is found at about 1 V bias voltage. In addition, the response and recovery times were determined to be around 55 s and 160 s, respectively. Finally, the structure shows a reversible response for low gas concentration at room temperature.

Keffous, A.; Cheriet, A.; Hadjersi, T.; Boukennous, Y.; Gabouze, N.; Boukezzata, A.; Belkacem, Y.; Kechouane, M.; Kerdja, T.; Menari, H.; Berouaken, M.; Talbi, L.; Ouadah, Y.

2013-01-01

271

Response time based output of metal oxide gas sensors applied to evaluation of meat freshness with neural signal analysis  

Microsoft Academic Search

The resistance response to a steep change of the composition in air is investigated for gas sensors based on metal oxide thin films after the target odour was injected from the chicken meat into the atmosphere of clean air. The change of the response is described using an exponential decrease with few time constants for the slope. The time constants

A Galdikas; A Mironas; A etkus; D Zelenin

2000-01-01

272

Experimental investigation of film cooling effectiveness on gas turbine blades  

E-print Network

The hot gas temperature in gas turbine engines is far above the permissible metal temperatures. Advanced cooling technologies must be applied to cool the blades, so they can withstand the extreme conditions. Film cooling is widely used in modern...

Gao, Zhihong

2009-05-15

273

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

274

Co-polymer films for sensors  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

275

Highly selective gas sensor arrays based on thermally reduced graphene oxide  

NASA Astrophysics Data System (ADS)

The electrical properties of reduced graphene oxide (rGO) have been previously shown to be very sensitive to surface adsorbates, thus making rGO a very promising platform for highly sensitive gas sensors. However, poor selectivity of rGO-based gas sensors remains a major problem for their practical use. In this paper, we address the selectivity problem by employing an array of rGO-based integrated sensors instead of focusing on the performance of a single sensing element. Each rGO-based device in such an array has a unique sensor response due to the irregular structure of rGO films at different levels of organization, ranging from nanoscale to macroscale. The resulting rGO-based gas sensing system could reliably recognize analytes of nearly the same chemical nature. In our experiments rGO-based sensor arrays demonstrated a high selectivity that was sufficient to discriminate between different alcohols, such as methanol, ethanol and isopropanol, at a 100% success rate. We also discuss a possible sensing mechanism that provides the basis for analyte differentiation.

Lipatov, Alexey; Varezhnikov, Alexey; Wilson, Peter; Sysoev, Victor; Kolmakov, Andrei; Sinitskii, Alexander

2013-05-01

276

Highly selective gas sensor arrays based on thermally reduced graphene oxide.  

PubMed

The electrical properties of reduced graphene oxide (rGO) have been previously shown to be very sensitive to surface adsorbates, thus making rGO a very promising platform for highly sensitive gas sensors. However, poor selectivity of rGO-based gas sensors remains a major problem for their practical use. In this paper, we address the selectivity problem by employing an array of rGO-based integrated sensors instead of focusing on the performance of a single sensing element. Each rGO-based device in such an array has a unique sensor response due to the irregular structure of rGO films at different levels of organization, ranging from nanoscale to macroscale. The resulting rGO-based gas sensing system could reliably recognize analytes of nearly the same chemical nature. In our experiments rGO-based sensor arrays demonstrated a high selectivity that was sufficient to discriminate between different alcohols, such as methanol, ethanol and isopropanol, at a 100% success rate. We also discuss a possible sensing mechanism that provides the basis for analyte differentiation. PMID:23661278

Lipatov, Alexey; Varezhnikov, Alexey; Wilson, Peter; Sysoev, Victor; Kolmakov, Andrei; Sinitskii, Alexander

2013-06-21

277

LaserSPECks: : laser SPECtroscopic trace-gas sensor networks - sensor integration and applications  

Microsoft Academic Search

We introduce a novel laser spectroscopic trace-gas sensor platform, LaserSPECks that integrates recently developed miniature quartz-enhanced photoacoustic spectroscopy (QE- PAS) gas sensing technology. This universal platform uses infrared laser spectroscopy detect and quantify numerous gas species at part-per-million to part-per-billion (ppm-ppb) concentrations (2). Traditional gas sensing devices capable of the same sensitivity and specificity are several orders of mag- nitude

Stephen So; Farinaz Koushanfar; Anatoliy Kosterev; Frank Tittel

2007-01-01

278

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

279

Investigation of the Carbon Monoxide Gas Sensing Characteristics of Tin Oxide Mixed Cerium Oxide Thin Films  

PubMed Central

Thin films of tin oxide mixed cerium oxide were grown on unheated substrates by physical vapor deposition. The films were annealed in air at 500 C for two hours, and were characterized using X-ray photoelectron spectroscopy, atomic force microscopy and optical spectrophotometry. X-ray photoelectron spectroscopy and atomic force microscopy results reveal that the films were highly porous and porosity of our films was found to be in the range of 11.621.7%. The films were investigated for the detection of carbon monoxide, and were found to be highly sensitive. We found that 430 C was the optimum operating temperature for sensing CO gas at concentrations as low as 5 ppm. Our sensors exhibited fast response and recovery times of 26 s and 30 s, respectively. PMID:22736967

Durrani, Sardar M. A.; Al-Kuhaili, Mohammad F.; Bakhtiari, Imran A.; Haider, Muhammad B.

2012-01-01

280

Investigation of the carbon monoxide gas sensing characteristics of tin oxide mixed cerium oxide thin films.  

PubMed

Thin films of tin oxide mixed cerium oxide were grown on unheated substrates by physical vapor deposition. The films were annealed in air at 500 C for two hours, and were characterized using X-ray photoelectron spectroscopy, atomic force microscopy and optical spectrophotometry. X-ray photoelectron spectroscopy and atomic force microscopy results reveal that the films were highly porous and porosity of our films was found to be in the range of 11.6-21.7%. The films were investigated for the detection of carbon monoxide, and were found to be highly sensitive. We found that 430 C was the optimum operating temperature for sensing CO gas at concentrations as low as 5 ppm. Our sensors exhibited fast response and recovery times of 26 s and 30 s, respectively. PMID:22736967

Durrani, Sardar M A; Al-Kuhaili, Mohammad F; Bakhtiari, Imran A; Haider, Muhammad B

2012-01-01

281

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

282

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

283

Ultrathin porous carbon films as amperometric transducers for biocatalytic sensors  

SciTech Connect

Novel ultrathin (0.4 [mu]m) porous carbon films are employed as transducers for amperometric biosensors. Such foamlike nanoscopic films couple the advantages of high enzyme loadings (within the micropore hosts) and large microscopic area with a small geometric area. Both electropolymerization and metalization are used to entrap the enzyme within the micropores. Scanning electron microscopy sheds useful insights into the unique morphology of the growing enzyme layer. The greatly enhanced sensitivity is coupled with a fast and stable response. Factors influencing the performance of porous-film-based biosensors are examined and discussed. The improved performance is illustrated in connection with glucose and phenol sensors. The latter offers a remarkably low detection limit of 2.5 x 10[sup [minus]8] M. The new nanoscopic foams should prove useful for many other electroanalytical applications. 11 refs., 7 figs.

Wang, J.; Chen, Q. (New Mexico State Univ., Las Cruces, NM (United States)); Renschler, C.L.; White, C. (Sandia National Lab., Albuquerque, NM (United States))

1994-07-01

284

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

285

Optimized temperature modulation of micro-hotplate gas sensors through pseudorandom binary sequences  

Microsoft Academic Search

In recent years, modulating the working temperature of metal-oxide gas sensors has been one of the most widely used methods to enhance sensor selectivity. When the working temperature of a gas sensor is modulated, the kinetics of the gas-sensor interaction are altered, and this leads to characteristic response patterns. Many works have shown that it is possible to identify and

Alexander Vergara; Eduard Llobet; Jess Brezmes; Xavier Vilanova; Peter Ivanov; Isabel Grcia; Carles Can; Xavier Correig

2005-01-01

286

Metal oxide-based gas sensor and microwave broad-band measurements: an innovative approach to gas sensing  

Microsoft Academic Search

We outline the development of a gas sensor using microwave technology (0.3 MHz to 3 GHz). The sensor is a coaxial structure into which is introduced a sensitive material. An electromagnetic field (microwave), sent out through the sensor by a vectorial network analyzer, solicits the sensitive material exposed to a gas. The observed variation in the sensor response is due

Julien Jouhannaud; J. Rossignol; D. Stuerga

2007-01-01

287

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

288

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 May 2004 to October 2004 including testing of catalytic materials, sensor design and fabrication, and software development.

Palitha Jayaweera

2004-05-01

289

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

290

Parallel Beam Micro Sensor\\/Actuator Unit Using PZT Thin Films and its Application Examples  

Microsoft Academic Search

Piezoelectric materials are used for sensors and actuators. It is difficult to form complicated structures with piezoelectric materials, so the actuators and sensors are simple. Using the hydrothermal method, we can fabricate PZT thin film on a three dimensional titanium substrate. We use this feature for actuators and sensors, and made a new sensor\\/actuator unit using this method on a

Toshio Fukuda; Hiroshi Sato; Fumihito Arai; Hitoshi Iwata; Kouichi Itoigawa

1998-01-01

291

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

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

2014-11-01

292

Fast, selective, and stable high temperature humidity sensors enabled by microfabricated yttrium-doped barium zirconate thin films  

NASA Astrophysics Data System (ADS)

This work tested the viability of microfabricated humidity sensors based on Y-doped BaZrO3 by developing thin film deposition processes, fabricating devices, and characterizing the device response. At high temperatures, this material becomes conductive depending on temperature, water vapor, and other gas concentrations. Such devices should help increase efficiency and decrease emissions through improved combustion process control. Using microfabrication may lead to reduced size and faster sensor response. Two hundred and twelve variations of thin film layers were deposited and characterized out of which 112 were used in sensors. BaZrO3:Y thin films (200--750 nm) were sputtered onto oxidized n-type silicon substrates at room temperature from a ceramic target in an Ar sputtering ambient. Various deposition pressures and powers were used to correlate process parameters with film properties. Films were annealed at 800 and 1000C (3 hours, air) and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) to determine microstructure, surface morphology, and film composition. For comparison, 30--500 nm thick films were deposited onto identical substrates using PLD (various substrate temperatures) and characterized as deposited. Selected samples were annealed at 1000C (3 hours in air) and characterized again. Transmission electron microscopy (TEM) of 30 and 50 nm PLD films confirmed the particle sizes found by AFM of 19--25 nm. Although all layers show Barium deficiencies, stable process windows were established for sputtering and PLD close to stoichiometric compositions. Sensors with the sensitive material deposited on top of the interdigitated test structure (IDE) showed no response to changes in humidity. Sensors with the IDE placed on top of the sensing film showed sensitive response, suggesting a strong surface dominated sensing effect. Ti/Pt as contact metal yielded an unrepeatable humidity response. Cr/Au gave sensitive, selective, and long term stable humidity response. All films were exposed to varying partial pressures of water vapor, (400 to 650C) with and without exhaust gas mixtures. Sensitivities of 0.2 to 62 atm-1 were demonstrated with tenfold selectivity towards other gases and sensor life time in excess of a year. Response times are 4--20 times faster than reports in literature.

Chen, Xiaoxin

293

Gas sensors characterization and multilayer perceptron (MLP) hardware implementation for gas identification using a Field Programmable Gate Array (FPGA).  

PubMed

This paper develops a primitive gas recognition system for discriminating between industrial gas species. The system under investigation consists of an array of eight micro-hotplate-based SnO2 thin film gas sensors with different selectivity patterns. The output signals are processed through a signal conditioning and analyzing system. These signals feed a decision-making classifier, which is obtained via a Field Programmable Gate Array (FPGA) with Very High-Speed Integrated Circuit Hardware Description Language. The classifier relies on a multilayer neural network based on a back propagation algorithm with one hidden layer of four neurons and eight neurons at the input and five neurons at the output. The neural network designed after implementation consists of twenty thousand gates. The achieved experimental results seem to show the effectiveness of the proposed classifier, which can discriminate between five industrial gases. PMID:23529119

Benrekia, Fayal; Attari, Mokhtar; Bouhedda, Mounir

2013-01-01

294

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

295

Verification of a logarithmic model for estimation of gas concentrations in a mixture for a tin oxide gas sensor response  

Microsoft Academic Search

Changes in electrical conductivity due to a reaction occurring between the original adsorbents and the gases present in the surrounding atmosphere were measured for a tin dioxide-based gas sensor. In this study, a model of the gas sensor response using a relationship between the gas concentration in a mixture and the sensor resistance is proposed. The values of coefficients are

Shigeki Hirobayashi; Mohammed Afrose Kadir; Toshio Yoshizawa; Tatsuo Yamabuchi

2003-01-01

296

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

297

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

298

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

299

Physical characteristics of polyimide films for flexible sensors  

NASA Astrophysics Data System (ADS)

Physical characteristics of polyimide films, including optical, micro/nano mechanical, and thermophysical characteristics were investigated using a photometric, a nanoindentation, and a thermomechanical analyzer for applications in flexible sensors. Experimental results show that UV light cannot transmit into the polyimide films. The transmittances, with a maximum of about 86%, at VIS and near IR lights decrease with increasing PI film thicknesses. The mechanical characteristics were determined using tensile, bending moment, and nanoindentation testing. The stress-strain curve approximated bilinear characteristics, the load-unload bending moment exhibited hysteresis, and nanoindentation generated elastic energy dissipation in the loading-unloading region. Nanoindentation showed an almost uniform hardness and a reduced Youngs modulus of about 0.1810.03 and 3.210.06 GPa, respectively, when the penetrating depth was more than about 2 ?m. Thermophysical characteristics were greatly influenced on 8.3 and 25 ?m specimens due to the higher relaxation of thin PI films. The thermal expansion remained steady when the thickness was over 50 ?m. The results show that PI films have potential in flexible sensing and higher temperature fabrication.

Chang, Wen-Yang; Fang, Te-Hua; Lin, Yu-Cheng

2008-08-01

300

Calibration methods of carbon nanotube gas sensor for partial discharge detection in SF\\/sub 6  

Microsoft Academic Search

The authors proposed a new type of gas sensor for high sensitive detection of decomposition products generated by partial discharge (PD) in SF\\/sub 6\\/ gas. The sensor employed carbon nanotubes (CNTs) as gas sensing transducer and was fabricated by electrokinetic manipulation of CNTs using dielectrophoresis. Due to complicated gas decomposition process of SF\\/sub 6\\/ gas, calibration of the CNT gas

Weidong Ding; Ryota Hayashi; Junya Suehiro; Guangbin Zhou; Kiminobu Imasaka; Masanori Hara

2006-01-01

301

Optical control and diagnostics sensors for gas turbine machinery  

NASA Astrophysics Data System (ADS)

There exists a vast range of optical techniques that have been under development for solving complex measurement problems related to gas-turbine machinery and phenomena. For instance, several optical techniques are ideally suited for studying fundamental combustion phenomena in laboratory environments. Yet other techniques hold significant promise for use as either on-line gas turbine control sensors, or as health monitoring diagnostics sensors. In this paper, we briefly summarize these and discuss, in more detail, some of the latter class of techniques, including phosphor thermometry, hyperspectral imaging and low coherence interferometry, which are particularly suited for control and diagnostics sensing on hot section components with ceramic thermal barrier coatings (TBCs).

Trolinger, James D.; Jenkins, Thomas P.; Heeg, Bauke

2012-10-01

302

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 (100600 ) were evaporated as activator layers onto WO3 thin films and Al layers (1500 ) 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

303

Film Sensor Device Fabricated by a Piezoelectric Poly(L-lactic acid) Film  

NASA Astrophysics Data System (ADS)

Synthetic piezoelectric polymer films produced from petroleum feedstock have long been used as thin-film sensors and actuators. However, the fossil fuel requirements for synthetic polymer production and carbon dioxide emission from its combustion have raised concern about the environmental impact of its continued use. Eco-friendly biomass polymers, such as poly(L-lactic acid) (PLLA), are made from plant-based (vegetable starch) plastics and, thus, have a much smaller carbon footprint. Additionally, PLLA does not exhibit pyroelectricity or unnecessary poling. This suggests the usefulness of PLLA films for the human-machine interface (HMI). As an example of a new HMI, we have produced a TV remote control using a PLLA film. The intuitive operation provided by this PLLA device suggests that it is useful for the elderly or handicapped.

Ando, Masamichi; Kawamura, Hideki; Kageyama, Keisuke; Tajitsu, Yoshiro

2012-09-01

304

Detection of Smoldering Fire Using Tin Oxide Gas Sensors  

NASA Astrophysics Data System (ADS)

Detecting technique of smoldering fire was examined using tin oxide gas sensors. Eight sensors were installed in a room. They were same type. Four kinds of materials were adopted as a fire-source material. The materials were cotton cloth, wallpaper, curtain cloth and woodchip, which were main smoldering fire-source materials in an indoor environment. The sensor outputs to gases evolved upon the smoldering fire of the materials were measured. The differential characteristic of the output was derived to analyze. As for the results, it became obvious that the sensor locating at higher position had a higher sensitivity and it could sense the fire instantaneously. It is thought that the generated gases rise up directly toward the ceiling and reflect downward. A small type of electric cooking stove was used as a fire-source. The surface temperature of the stove plate arrived at 340 C. A bar was adopted to set the sensors freely. In this experiment, three bars were adopted and the heights of the sensor position were 50, 100, 150 and 200 cm from the floor. It is effective to locate the sensor at higher position in detecting a smoldering fire. The sensor characteristics were analyzed using principal component analysis (PCA). The system could discriminate source materials among wallpaper, woodchip and curtain for smoldering fire by utilizing the result of PCA. But, the smoldering fire of cotton cloth could not be distinguished from that of curtain by this system. Each fire could be identified in four minutes.

Higashino, Tsubasa; Sawada, Ayako; Oyabu, Takashi; Takei, Yoshinori; Nanto, Hidehito; Toko, Kiyoshi

305

?-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 10MHz. 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 (0.08-8U/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

2014-09-21

306

Acoustoelectric Effect on the Responses of SAW Sensors Coated with Electrospun ZnO Nanostructured Thin Film  

PubMed Central

In this study, zinc oxide (ZnO) was a very good candidate for improving the sensitivity of gas sensor technology. The preparation of an electrospun ZnO nanostructured thin film on a 433 MHz Rayleigh wave based Surface Acoustic Wave (SAW) sensor and the investigation of the acoustoelectric effect on the responses of the SAW sensor are reported. We prepared an electrospun ZnO nanostructured thin film on the SAW devices by using an electrospray technique. To investigate the dependency of the sensor response on the structure and the number of the ZnO nanoparticles, SAW sensors were prepared with different coating loads. The coating frequency shifts were adjusted to fall between 100 kHz and 2.4 MHz. The sensor measurements were performed against VOCs such as acetone, trichloroethylene, chloroform, ethanol, n-propanol and methanol vapor. The sensor responses of n-propanol have opposite characteristics to the other VOCs, and we attributed these characteristics to the elastic effect/acoustoelectric effect.

Tasaltin, Cihat; Ebeoglu, Mehmet Ali; Ozturk, Zafer Ziya

2012-01-01

307

Modeling and fabrication of a planar thin film airflow sensor  

NASA Astrophysics Data System (ADS)

A thin film airflow transducer based on the hot wire anemometer principle was designed using current MEMS modelling & simulation software. Flow sensors are commonly implemented with thermal isolation of the sensor from the bulk substrate mass using methods such as reverse side etching or sacrificial layers, however this paper will present a sensor relying on thermal insulation only. This insulation may be provided by layers of material exhibiting relatively poor thermal conduction characteristics such as silicon dioxide or polyimide, giving rise to a number of advantages such as removing the process of reverse side etching. Limiting fabrication to use of simple processes such as photolithography and sputtering/evaporative deposition also simplifies this design and assists in greatly increasing the compatibility with standard CMOS fabrication processes and materials. A combination of both theoretical computer modelling and physical fabrication and testing has been the approach to this research. Preliminary testing of this design has demonstrated small yet measurable temperature gradients across the device surface during steady state operation. The novel approach to this device is the investigation of pulsed operation, effectively a transient analysis that allows the thermal conduction effects of the bulk mass to be significantly reduced, leading to a significant increase of both efficiency and response time. Electro-thermo-mechanical and computational fluid dynamic analysis of the structure successfully model the thermal conduction, radiation and forced convection effects of the device during and after ohmic heating of the sensor's heating element.

Adamec, Richard J.; Tanner, Philip G.; Thiel, David V.

2001-11-01

308

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.

309

Structure of Palladium Nanoclusters for Hydrogen Gas Sensors  

Microsoft Academic Search

Palladium nanoclusters produced by inert gas aggregation\\/magnetron sputtering are used as building blocks for the construction of nano electronic devices with large surface to volume ratios that can be used as sensitive hydrogen gas sensors in fuel cells and in petrochemical plants. X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and high resolution transmission electron microscopy (HRTEM) have been

K. J. Stevens; B. Ingham; M. F. Toney; S. A. Brown; A. Lassesson

2009-01-01

310

Structure of palladium nanoclusters for hydrogen gas sensors  

Microsoft Academic Search

Palladium nanoclusters produced by inert gas aggregation\\/magnetron sputtering are used as building blocks for the construction of nano electronic devices with large surface to volume ratios that can be used as sensitive hydrogen gas sensors in fuel cells and in petrochemical plants. X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and high resolution transmission electron microscopy (HRTEM) have been

K. J. Stevens; B. Ingham; M. F. Toney; S. A. Brown; A. Lassesson

2008-01-01

311

Pt\\/graphene nano-sheet based hydrogen gas sensor  

Microsoft Academic Search

In this paper, we present gas sensing properties of Pt\\/graphene-like nano-sheets towards hydrogen gas. The graphene-like nano-sheets were produced via the reduction of spray-coated graphite oxide deposited on SiC substrates by hydrazine vapor. Structural and morphological characterizations of the graphene sheets were analyzed by scanning electron and atomic force microscopy. Current-voltage and dynamic responses of the sensors were investigated towards

M. Shafiei; R. Arsat; J. Yu; K. Kalantar-zadeh; W. Wlodarski; S. Dubin; R. B. Kaner

2009-01-01

312

Numerical analysis on nanoparticles-laden gas film thrust bearing  

NASA Astrophysics Data System (ADS)

Nanoparticles can be taken as additives and added into various fluids to improve their lubricating performances. At present, researches in this area are mainly concentrated on the improvement effects of nanoparticles on the lubricating performances of liquid such as oil and water. Nanoparticles will also affect gas lubrication, but few related studies have been reported. Nanoparticles-laden gas film (NLGF) is formed when adding nanoparticles into gas bearing. Then, the lubricating performances of gas bearing including pressure distribution and load-carrying capacity will change. The variations of pressure distribution and load-carrying capacity in nanoparticles-laden gas film thrust bearing are investigated by numerical method. Taking account of the compressibility of gas and the interactions between gas and nanoparticles, a computational fluid dynamics model based on Navier-Stokes equations is applied to simulate the NLGF flow. The effects of inlet nanoparticles volume fraction and orifice radius on film pressure distribution and load-carrying capacity of the NLGF are calculated. The numerical calculation results show that both of the film land pressure and the maximum film pressure both increase when the nanoparticles are added into gas bearing, and the film pressures increase with the rising of the inlet nanoparticles volume fraction. The nanoparticles have an enhancement effect on load-carrying capacity of the studied bearing, and the enhancement effect becomes greater as the film thickness decrease. Therefore, nanoparticles can effectively improve the lubricating performance of gas bearing. The proposed research provides a theoretical basis for the design of new-type nanoparticles-laden gas film bearings.

Yang, Zhiru; Diao, Dongfeng; Yang, Lei

2013-07-01

313

Surface plasmonic polaritonic sensor using a dielectric columnar thin film  

NASA Astrophysics Data System (ADS)

The propagation of a surface plasmon polariton (SPP) wave can be guided by the interface of a metal and a columnar thin film (CTF). Theory predicts that the angle of incidence on the prism/metal interface in the Turbadar-Kretschmann-Raether prism-coupled configuration required to excite the SPP wave shifts upon infiltration of the CTF by a fluid. Otherwise identical CTFs of different thicknesses were partnered with dense thin films of aluminum in optical experiments. The angle of incidence for exciting the SPP wave was found to shift to a higher value each time the CTF was infiltrated by a fluid of refractive index of increasing value. Experimental data indicated that the sensor offers a state-of-research sensitivity, thereby proving that a CTF can be a useful platform for SPP-wave-based optical sensing.

Swiontek, Stephen E.; Faryad, Muhammad; Lakhtakia, Akhlesh

2014-01-01

314

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

315

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

316

Carbon nanotube gas sensor conductance model, sensing mechanism analysis, and applications in flexible sensors and wireless sensors  

NASA Astrophysics Data System (ADS)

In this dissertation, the electrical property dependency of carbon nanotubes (CNTs) upon the humidity and chemical gas concentration is investigated. The electrical response of single-walled carbon nanotube (SWNT) networks to different humidity levels and gas molecules of ammonia (NH3) and nitrogen dioxide (NO2) at different concentrations was characterized by a sensor test system. In order to exclude the effect from contact resistance, the sheet resistance of SWNT networks was measured by transfer length method. The gas molecules concentration dependence of electrical property was analyzed, and two electrical models were proposed based on carrier transportation and adsorption isotherm respectively for different gas molecules. The electrical properties of SWNT networks estimated by the models were compared with the experimental data. The results show the models agree well with the experimental data. The primary objective of the sensor model is to understand the relationship between conductance of CNT networks and gas concentration. With this understanding, the model offers a precise measurement of the gas concentration based upon the electrical property of SWNT sensor. In addition, the mechanism of gas molecule adsorption on CNT networks is analyzed based on the conductance models. It is found that the conductance change of SWNT networks, induced by different humidity levels, is dominated by the thermal activation carrier hopping over the barriers between SWNTs. The average separation between the SWNTs increases linearly with the humidity levels. By contrast, when exposed to different NH3 and NO2, the conductance change is primarily determined by the charge transfer between gas molecules and CNTs. It shows that chemical molecules adsorption on the surface wall of SWNT causes the charge transfer. Furthermore, we investigated printed flexible electronics based on SWNTs and printable SWNT-based Frequency modulation (FM) passive wireless sensor tag on a flexible substrate with enhanced sensitivity. In this dissertation, we report a high sensitive flexible SWNT chemical gas sensor, capable of being easily fabricated. The sensor also shows good performance in linearity and flexibility. The flexible printed SWNT sensor with high sensitivity, low LOD and flexibility provides a promising solution to low-cost flexible sensor with high performance for mass production. Last, we developed a printable SWNT-based passive FM wireless sensor tag on a flexible substrate for ammonia detection. The FM wireless sensor tag shows an enhanced sensitivity and also exhibits a high linearity between the frequency shift and the logarithm of the chemical gas concentration. The linear response allows one to precisely predict the NH3 concentration by measuring the frequency shift of the FM wireless sensor tag. The experimental demonstration of the passive wireless sensor tag and accurate measurement of the NH3 concentration levels indicate that the FM modulated passive wireless sensor tag is promising for power-less standalone low-level NH3 sensing and monitoring.

Ling, Yunfeng

317

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

318

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

319

Gas sensor array for blueberry fruit disease detection and classification  

Microsoft Academic Search

A conducting polymer gas sensor array (electronic nose) was evaluated for detecting and classifying three common postharvest diseases of blueberry fruit: gray mold caused by Botrytis cinerea, anthracnose caused by Colletotrichum gloeosporioides, and Alternaria rot caused by Alternaria sp. Samples of ripe rabbiteye blueberries (Vaccinium virgatum cv. Brightwell) were inoculated individually with one of the three pathogens or left non-inoculated,

Changying Li; Gerard W. Krewer; Pingsheng Ji; Harald Scherm; Stanley J. Kays

2010-01-01

320

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

321

ZnO nanomaterials based SAW ethanol gas sensor  

Microsoft Academic Search

In this paper, ZnO nanomaterials with high effective specific surface area have been prepared and subsequently deposited on the SAW transducer as sensitive layer, finally the responses of the sensor to different ethanol gas concentrations were investigated at room temperature.

Y. Wu; X. Li; J. H. Liu; L. M. Yu; X. D. Hu

2010-01-01

322

A novel ozone detection at room temperature through UV-LED-assisted ZnO thick film sensors  

Microsoft Academic Search

In this work a novel ozone detection at room temperature (RT) has been investigated. Two functional materials, ZnO and (W0.9Sn0.1)O3?x (WS10) oxides, have been synthesized to prepare thick film gas sensors, both used in conventional heated mode as well as at RT assisted by UV irradiation. As a source of light, a light emitting diode (LED) of 400nm peak wavelength

M. C. Carotta; A. Cervi; A. Fioravanti; S. Gherardi; A. Giberti; B. Vendemiati; D. Vincenzi; M. Sacerdoti

323

Fast, selective, and stable high temperature humidity sensors enabled by microfabricated yttrium-doped barium zirconate thin films  

Microsoft Academic Search

This work tested the viability of microfabricated humidity sensors based on Y-doped BaZrO3 by developing thin film deposition processes, fabricating devices, and characterizing the device response. At high temperatures, this material becomes conductive depending on temperature, water vapor, and other gas concentrations. Such devices should help increase efficiency and decrease emissions through improved combustion process control. Using microfabrication may lead

Xiaoxin Chen

2010-01-01

324

Functionalised zinc oxide nanowire gas sensors: Enhanced NO2 gas sensor response by chemical modification of nanowire surfaces  

PubMed Central

Summary Surface coating with an organic self-assembled monolayer (SAM) can enhance surface reactions or the absorption of specific gases and hence improve the response of a metal oxide (MOx) sensor toward particular target gases in the environment. In this study the effect of an adsorbed organic layer on the dynamic response of zinc oxide nanowire gas sensors was investigated. The effect of ZnO surface functionalisation by two different organic molecules, tris(hydroxymethyl)aminomethane (THMA) and dodecanethiol (DT), was studied. The response towards ammonia, nitrous oxide and nitrogen dioxide was investigated for three sensor configurations, namely pure ZnO nanowires, organic-coated ZnO nanowires and ZnO nanowires covered with a sparse layer of organic-coated ZnO nanoparticles. Exposure of the nanowire sensors to the oxidising gas NO2 produced a significant and reproducible response. ZnO and THMA-coated ZnO nanowire sensors both readily detected NO2 down to a concentration in the very low ppm range. Notably, the THMA-coated nanowires consistently displayed a small, enhanced response to NO2 compared to uncoated ZnO nanowire sensors. At the lower concentration levels tested, ZnO nanowire sensors that were coated with THMA-capped ZnO nanoparticles were found to exhibit the greatest enhanced response. ?R/R was two times greater than that for the as-prepared ZnO nanowire sensors. It is proposed that the ?R/R enhancement in this case originates from the changes induced in the depletion-layer width of the ZnO nanoparticles that bridge ZnO nanowires resulting from THMA ligand binding to the surface of the particle coating. The heightened response and selectivity to the NO2 target are positive results arising from the coating of these ZnO nanowire sensors with organic-SAM-functionalised ZnO nanoparticles. PMID:23016141

Chang, Jin; Ponzoni, Andrea; Concina, Isabella; Zappa, Dario; Comini, Elisabetta; Motta, Nunzio; Faglia, Guido; Sberveglieri, Giorgio

2012-01-01

325

Hierarchical nanostructured semiconductor porous materials for gas sensors  

Microsoft Academic Search

Gas sensitive layers with a fractal structure based on tin oxide were prepared by the solgel-method. Investigations of the film structure were carried out by atomic force microscopy. The basic evolution steps of this fractal system were found to be diffusion-limited aggregation, clustercluster aggregation, formation of percolating transition and netting nanostructures. Gas-sensitivity measurements of synthesized samples were taken. The emergence

Vyacheslav A. Moshnikov; Irina E. Gracheva; Vladimir V. Kuznezov; Alexsandr I. Maximov; Svetlana S. Karpova; Alina A. Ponomareva

2010-01-01

326

Magnetic sensor based on side-polished fiber Bragg grating coated with iron film  

Microsoft Academic Search

A novel optical fiber magnetic sensor based on a side-polished fiber Bragg grating (FBG) coated with thin iron film was investigated. The sensor consists of a side-polished 10 mm FBG and two-layer thin iron films deposited on an interaction section 20 mum in diameter.

C. Tien; C. Hung; H. Chen; W. Liu; S. Lin

2006-01-01

327

Gas sensors based on single-wall carbon nanotubes and polypyrrole-coated carbon nanotubes  

Microsoft Academic Search

We have fabricated gas sensors based on single-wall carbon nanotubes and detected NH3 and NO2 gas. At the room temperature, the absorbed gas molecules are not easily detached from the CNT surface. So, we have testes the gas sensor at high temperatures and investigated the temperature dependences of electrical properties of CNTs above the room temperatures. Depending on the gas

Young Wook Chang; Je Seung Oh; Seung Hwan Yoo; Ji Hun Kim; Hyang Hee Choi; Kyung-Hwa Yoo

2007-01-01

328

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

329

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

330

Radiopacity of endodontic materials on film and a digital sensor.  

PubMed

The purpose of this study was to compare the radiographic appearance of 12 endodontic materials as visualized on either Kodak Ultra-speed D speed film (Eastman Kodak Company, Rochester, NY) or a Gendex eHD digital sensor (Gendex Dental Systems, Milan, Italy). Ten discs of each material were radiographed alongside an aluminum alloy 1100 (Alcoa, Pittsburgh, PA) stepwedge that was used for reference. For every radiograph, the average grayscale value of the material was converted into absorbance notation and compared with that of the reference stepwedge in order to determine the equivalent radiopacity in terms of millimeters of Al 1100 per millimeter of material. Two-way repeated-measures analysis of variance testing detected significant differences with respect to imaging system, material, and the interaction of the two factors (p < 0.001). The difference in a material's radiopacity as measured on the digital sensor compared with film was greater than 10% for 4 of the 12 materials and over 40% for InnoEndo (Heraus Kulzer, Armonk, NY). It was speculated that barium fillers cause this effect. PMID:17931942

Rasimick, Brian J; Shah, Rinal P; Musikant, Barry Lee; Deutsch, Allan S

2007-09-01

331

Sensor for measuring the oxygen content in the exhaust gas of combustion engines and method thereof  

Microsoft Academic Search

An improved lambda sensor is disclosed for the measurement of the oxygen content in the exhaust gas of internal combustion engines in which the sensor element is provided with a gas permeable wrapping coated with a catalyst. The sensor delivers a clear well defined signal in the so-called rich exhaust gas, which makes possible a more precise adjustment of the

A. Bozon; E. Koberstein; H. Pletka; H. Voelker

1982-01-01

332

Meander-shaped magnetoimpedance sensor for measuring inhomogeneous magnetic fringe fields of NiFe films  

NASA Astrophysics Data System (ADS)

Magnetic fringe fields of NiFe films were measured by giant magnetoimpedance (GMI) sensor, in this work. We have observed an interesting GMI phenomenon: the impedance enhanced first and then declined due to the presence of NiFe films, it is suggested that magnetic fringe fields have strengthened the longitudinal external magnetic field. Results indicated that the GMI sensor was able to quantify the magnetized NiFe films from 1 5 to 5 5 mm2. Anyway, this study has extended the application of GMI sensor to film detection, which makes it promising in detecting the defects of soft magnetic devices.

Wang, Tao; Lei, Chong; Yang, Zhen; Sun, Xuecheng; Liu, Yan; Zhou, Yong

2014-10-01

333

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; Rodrguez-Lujn, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramn

2014-01-01

334

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

335

Fabrication and characterization of high-temperature microreactors with thin film heater and sensor patterns in silicon nitride tubes.  

PubMed

In this paper the fabrication and electrical characterization of a silicon microreactor for high-temperature catalytic gas phase reactions, like Rh-catalyzed catalytic partial oxidation of methane into synthesis gas, is presented. The microreactor, realized with micromachining technologies, contains silicon nitride tubes that are suspended in a flow channel. These tubes contain metal thin films that heat the gas mixture in the channel and sense its temperature. The metal patterns are defined by using the channel geometry as a shadow mask. Furthermore, a new method to obtain Pt thin films with good adhesive properties, also at elevated temperatures, without adhesion metal is implemented in the fabrication process. Based on different experiments, it is concluded that the electrical behaviour at high temperatures of Pt thin films without adhesion layer is better than that of Pt/Ta films. Furthermore, it is found that the temperature coefficient of resistance (TCR) and the resistivity of the thin films are stable for up to tens of hours when the temperature-range during operation of the microreactor is below the so-called "burn-in" temperature. Experiments showed that the presented suspended-tube microreactors with heaters and temperature sensors of Pt thin films can be operated safely and in a stable way at temperatures up to 700 degrees C for over 20 h. This type of microreactor solves the electrical breakdown problem that was previously reported by us in flat-membrane microreactors that were operated at temperatures above 600 degrees C. PMID:15726209

Tiggelaar, R M; Berenschot, J W; de Boer, J H; Sanders, R G P; Gardeniers, J G E; Oosterbroek, R E; van den Berg, A; Elwenspoek, M C

2005-03-01

336

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

337

Chip scale packaging of piezoresistive pressure sensors using dry-film shielding  

Microsoft Academic Search

In this study, a chip scale packaging (CSP) of piezoresistive pressure sensors using a dry-film shielding approach is demonstrated. A sensing-channel just above the silicon membrane of the pressure sensor has to be reserved in the package body. To prevent the silicon membrane of the pressure sensors from the metal-deposition contaminations, a dry-film with a redistribution pattern is used to

Tyson Huang; Lung-Tai Chen; Peter Chu; Y. S. Chen; C. W. Ho; Chung-Yi Hsu; Jason Pan

2009-01-01

338

Polyvinylidene fluoride film sensors in collocated feedback structural control: application for suppressing impact-induced disturbances  

Microsoft Academic Search

Polyvinylidene fluoride (PVDF) films are light, flexible, and have high piezoelectricity. Because of these advantages, they have been widely used as sensors in applications such as underwater investigation, nondestructive damage detection, robotics, and active vibration suppression. PVDF sensors are especially preferred over conventional strain gauges in active vibration control because the PVDF sensors are easy to cut into different sizes

Chien-Ching Ma; Kuo-Chih Chuang; Shan-Ying Pan

2011-01-01

339

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

340

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 100600C. 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

341

Characterization of molecular recognition in gas sensors  

SciTech Connect

Molecular recognition is an important topic when searching for new, selective coating materials for chemical sensing. Recently, the general idea of molecular recognition in the gas phase was challenged by Grate et al. However, in earlier thickness-shear mode resonator (TSMR) investigations, convincing evidence was presented for specific recognition of particular analyte target molecules. In this study, the authors systematically investigated coatings previously shown to be highly selective, such as the bucket-like cyclodextrins for chiral recognition, Ni-camphorates for the specific detection of the bases pyridine and DMMP (dimethylmethylphosphonate), and phthalocyanines to specifically detect benzene, toluene, and xylene (BTX).

Hierlemann, A.; Ricco, A.J. [Sandia National Labs., Albuquerque, NM (United States). Microsensor Research and Development Dept.; Bodenhoefer, K.; Goepel, W. [Univ. Tuebingen (Germany). Inst. fuer Physikalische und Theoretische Chemie

1998-08-01

342

Corrosion properties of sputter-deposited steel thin film for electrical resistance sensor material  

Microsoft Academic Search

Steel thin films for an electrical resistance sensor were prepared by sputter deposition. It was revealed that the electrochemical properties of the thin films were influenced by the surface roughness. Using an Al2O3 substrate with high surface roughness, it was possible to obtain a steel thin film with corrosion characteristics similar to bulk steel. The corrosion rate of the thin

Sungwon Jung; SeonYeob Li; Young-Geun Kim

2006-01-01

343

Tunnel-field-effect-transistor based gas-sensor: Introducing gas detection with a quantum-mechanical transducer  

E-print Network

Tunnel-field-effect-transistor based gas-sensor: Introducing gas detection with a quantum; published online 17 January 2013) A gas-sensor based on tunnel-field-effect-transistor (TFET) is proposed that leverages the unique current injection mechanism in the form of quantum-mechanical band-to-band tunneling

344

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 m-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

345

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

E-print Network

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

Simon, Dan

346

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

347

A highly integratable silicon thermal gas flow sensor  

NASA Astrophysics Data System (ADS)

Thermal flow sensors have been designed, fabricated, and characterized. All bulk material in these devices is silicon so that they are integratable in silicon-based microsystems. To mitigate heat losses and to allow for use of corrosive gases, the heating and sensing thin film titanium/platinum elements, injecting and extracting heat, respectively, from the flow, are placed outside the channel on top of a membrane consisting of alternating layers of stress-balancing silicon dioxide and silicon nitride. For the fabrication, an unconventional bond surface protection method using sputter-deposited aluminum instead of thermal silicon dioxide is used in the process steps prior to silicon fusion bonding. A method for performing lift-off on top of the transparent membrane was also developed. The sensors, measuring 9.5 9.5 mm2, are characterized in calorimetric and time-of-flight modes with nitrogen flow rates between 0 sccm and 300 sccm. The maximum calorimetric sensor flow signal and sensitivity are 0.95 mV and 29 V sccm-1, respectively, with power consumption less than 40 mW. The time-of-flight mode is found to have a wider detectable flow range compared with calorimetric mode, and the time of flight measured indicates a response time of the sensor in the millisecond range. The design and operation of a sensor with high sensitivity and large flow range are discussed. A key element of this discussion is the configuration of the array of heaters and gauges along the channel to obtain different sensitivities and extend the operational range. This means that the sensor can be tailored to different flow ranges.

Palmer, Kristoffer; Kratz, Henrik; Nguyen, Hugo; Thornell, Greger

2012-06-01

348

CMOS Monolithic MetalOxide Gas Sensor Microsystems  

Microsoft Academic Search

This paper presents two mixed-signal monolithic gas sensor microsystems fabricated in standard 0.8-$muhbox m$CMOS technology combined with post-CMOS micromachining to form the microhotplates. The on-chip microhotplates provide very high temperatures (between 200$^circ$C and 400$^circ$C), which are necessary for the normal operation of metaloxide sensing layers. The first microsystem has a single-ended architecture comprising a microhotplate (diameter of 300$muhbox m$) and

Diego Barrettino; Markus Graf; Stefano Taschini; Sadik Hafizovic; Christoph Hagleitner; Andreas Hierlemann

2006-01-01

349

Reduced graphene oxide for room-temperature gas sensors  

Microsoft Academic Search

We demonstrated high-performance gas sensors based on graphene oxide (GO) sheets partially reduced via low-temperature thermal treatments. Hydrophilic graphene oxide sheets uniformly suspended in water were first dispersed onto gold interdigitated electrodes. The partial reduction of the GO sheets was then achieved through low-temperature, multi-step annealing (100, 200, and 300 C) or one-step heating (200 C) of the device in

Ganhua Lu; Leonidas E. Ocola; Junhong Chen

2009-01-01

350

Solid State Gas Sensor for Volatile Organic Vapours  

Microsoft Academic Search

Nano Crystalline ZnO powders were synthesized by a Solvothermal method using propan-1ol as the reaction medium. Wurtzite-type ZnO powder has been synthesized by a Solvothermal method at low temperature with an aim to obtain nano crystalline ZnO and to study its ethanol and methanol gas sensing properties have been examined by nano crystalline Zinc oxide sensor in this study. The

Sk. Khadeer Pasha; K. Chidambaram

2009-01-01

351

Micro-cantilever array and its application in gas sensor  

Microsoft Academic Search

Micro-cantilever array was made by micromachining technology. Its mechanical characteristic was analyzed. A gas sensor based micro-cantilever array was presented. The different material sensing layers were fabricated on the different micro-cantilever surface respectively; the physical or chemical absorption alters the mass of micro-cantilever, accordingly, the mechanical characteristic of micro-cantilever was changed. The vibration characteristics of beam array and its changes

Wu Pan; Ning Li

2008-01-01

352

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, Fbio L.; Herrmann, Paulo S. P.

2011-01-01

353

Study on the measurement of oil-film pressure of engine main bearing by thin-film sensor The influence of bearing deformation on pressure sensor output under engine operation  

Microsoft Academic Search

In a previous paper, oil-film pressure in an engine main bearing was measured by a using thin-film Manganin sensor. This sensor had adequate sensitivity to strain and temperature in terms of measurement principle. In this study, more accurate measurement of oil-film pressure was allowed by the formation of the newly developed thin-film strain sensor made of Ni-Cr-Al at the same

Yuji Mihara; Makoto Kajiwara; Takayuki Fukamatsu; Tsuneo Someya

1996-01-01

354

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

355

Sensing gas molecules using graphitic nanoribbon films and networks  

NASA Astrophysics Data System (ADS)

We fabricate and study the gas sensing properties of graphitic nanoribbon (GNR) films and networks consisting of multi-layer graphene nanoribbons with an average width of 7 nm. We experimentally demonstrate the high sensitivity of these films and networks for sensing gas molecules at the parts-per-million (ppm) level, in particular hydrogen and ammonia. The sensing response exhibits excellent repeatability and full recovery in air. Furthermore, our results show that functionalization by metal nanoparticles could significantly improve the sensitivity. We characterize the sensing response at various temperatures, gas concentrations, recovery ambients, and film thicknesses. We find that the relative resistance response of the GNR films shows a power-law dependence on the gas concentration, which can be explained by the Freundlich isotherm. The activation energy obtained from the sensing experiments is consistent with the theoretical calculations of the adsorption energies of gas molecules on graphene sheets and nanoribbons. Their simple and low-cost fabrication process and good sensing response open up the possibility of using graphitic nanoribbon films and networks for large-scale sensing applications.

An, Yanbin; Johnson, Jason L.; Behnam, Ashkan; Pearton, S. J.; Ural, Ant

2011-03-01

356

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

357

Figure 1. Principle of wireless detection of gas centration with a chipless sensor.  

E-print Network

flexible and can be done with less effort, in comparison with a wired sensor network. In some special casesFigure 1. Principle of wireless detection of gas centration with a chipless sensor. A Novel Inkjet Printed Carbon Nanotube-Based Chipless RFID Sensor for Gas Detection Arnaud Vena#1 , Lauri Sydänheimo#2

Tentzeris, Manos

358

Gas sensing studies of pulsed laser deposition deposited WO3 nanorod based thin films.  

PubMed

WO3 nanorod based thin films were deposited via pulsed laser deposition onto quartz conductometric transducers with pre-patterned gold interdigitated transducers (IDT) employing the shortest wavelength (193 nm) ArF excimer laser. Micro-characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to study surface morphology and crystal structure. It was observed that the fabricated films showed nanocolumnar features perpendicular to the surface. The measured sizes of the nanorods were found to be approximately -50 nm in diameter. The high resolution TEM (HRTEM) image of the nanorods based WO3 showed the WO3 lattice spacing of 3.79 angstroms corresponding to the (020) plane of monoclinic WO3. Gas sensing characterizations of the developed sensors were tested towards hydrogen and ethanol at temperatures between room and 400 degrees C. The sensor exhibited high response towards H2 and ethanol at operating temperatures of 170 and 400 degrees C, respectively. The excellent sensing characteristics of WO3 films towards ethanol and H2 at low concentrations offer great potential for low cost and stable gas sensing. PMID:24266229

Ahmad, Muhammad Z; Kang, Joonhee; Zoolfakar, Ahmad S; Sadek, Abu Z; Wlodarski, Wojtek

2013-12-01

359

Hydrogen Sensor Based on RF-Sputtered Thermoelectric SiGe Film  

NASA Astrophysics Data System (ADS)

Si0.8Ge0.2 thin film was sputtered on an alumina substrate by the RF-sputtering method. After annealing in flowing Ar atmosphere, platinum film, which acts as a catalyst of the combustible sample gas, was further sputtered on half the surface area of SiGe film. The hydrogen-sensing properties were investigated for the development of potential applications of the device structure as a hydrogen sensor that makes use of the thermoelectric (TE) effect. The measurement results indicate that a reliable output voltage signal was successfully realized when the element was exposed to an environment with a certain hydrogen concentration. The operating temperature for the device was around 100C, and the response and recovery time corresponding to 90% voltage change were both shorter than 50 s on switching the atmosphere from synthetic air to 3% H2. The detectable concentration of the device ranged from 0.01% to 3%. Furthermore, a good selectivity to hydrogen was also exhibited.

Qiu, Fabin; Shin, Woosuck; Matsumiya, Masahiko; Izu, Noriya; Murayama, Norimitsu

2003-04-01

360

Single-layer MoSe2 based NH3 gas sensor  

NASA Astrophysics Data System (ADS)

High performance chemical sensor is highly desirable to detect traces of toxic gas molecules. Two dimensional (2D) transition metal dichalcogenides (TMDC) semiconducting materials has attracted as high performance gas sensor device applications due to unique properties such as high surface to volume ratio. Here, we describe the utilization of single-layer MoSe2 as high-performance room temperature NH3 gas sensors. Our single-layer MoSe2 based gas sensor device shows comprehensible detection of NH3 gas down to 50 ppm. We also confirmed gas sensing measurement by recording the Raman spectra before and after exposing the device to NH3 gas, which subsequently shows the shift due to charger transfer and analyte gas molecule adsorption on surface of single-layer MoSe2 nanosheet. Our investigations show the potential use of single-layer and few layer thick MoSe2 and other TMDC as high-performance gas sensors.

Late, Dattatray J.; Doneux, Thomas; Bougouma, Moussa

2014-12-01

361

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

362

High sensitivity ethanol gas sensor integrated with a solid-state heater and thermal isolation improvement structure for legal drink-drive limit detecting  

Microsoft Academic Search

The paper reports the successful fabrication of ethanol gas sensors with tin-dioxide (SnO2) thin films integrated with a solid-state heater, which is realized with technologies of micro-electro-mechanical systems (MEMS), and are compatible with VLSI processes. The main sensing part with dimensions of 450400 ?m2 in this developed device is composed of a sensing SnO2 film, which is fabricated by electron-gun

Jyh-Jier Ho; Y. K Fang; K. H Wu; W. T Hsieh; C. H Chen; G. S Chen; M. S Ju; Jing-Jenn Lin; S. B Hwang

1998-01-01

363

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

364

Foam films as thin liquid gas separation membranes.  

PubMed

In this letter, we testify the feasibility of using freestanding foam films as a thin liquid gas separation membrane. Diminishing bubble method was used as a tool to measure the permeability of pure gases like argon, nitrogen, and oxygen in addition to atmospheric air. All components of the foam film including the nature of the tail (fluorocarbon vs hydrocarbon), charge on the headgroup (anionic, cationic, and nonionic) and the thickness of the water core (Newton black film vs Common black film) were systematically varied to understand the permeation phenomena of pure gases. Overall results indicate that the permeability values for different gases are in accordance with magnitude of their molecular diameter. A smaller gaseous molecule permeates faster than the larger ones, indicating a new realm of application for foam films as size selective separation membranes. PMID:21314136

Ramanathan, Muruganathan; Mller, Hans Joachim; Mhwald, Helmuth; Krastev, Rumen

2011-03-01

365

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

366

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

367

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

368

Nano-clay/poly(vinylidene fluoride) composite films as sensor and actuator element  

NASA Astrophysics Data System (ADS)

Poly(vinylidene fluoride) (PVDF) is a piezoelectric polymer material. In general, it is necessary to give large stretch to PVDF film when PVDF film is used as sensor or actuator element. However, we recently found that PVDF shows piezoelectricity without large stretch if nano-clays are uniformly dispersed into it. The aim of present study is to investigate the possibilities of nano-clay/PVDF composite film as sensor and actuator element. Firstly, PVDF films and nano-clay/PVDF composite film are fabricated by solvent casting. Also, commercial PVDF film is prepared as comparative material. Secondarily, we investigate the change of electrical displacement according to the input voltage of triangle wave by using Sawyer-tower bridge circuit for PVDF films and nano-clay/PVDF composite film. Then, the change of impedance is also measured at broad frequency by using impedance analyzer. Thirdly, we apply the voltage of sine wave to fabricated films, and measure the output oscillation generated from films. Finally, we discuss the possibilities of nano-clay/PVDF composite film as sensor and actuator element.

Murasawa, Go; Wakabayashi, Daisuke; Yamada, Eiji; Nishioka, Akihiro; Miyata, Ken; Koda, Tomonori

2010-04-01

369

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

370

Tilted $c$Axis Thin-Film Bulk Wave Resonant Pressure Sensors With Improved Sensitivity  

Microsoft Academic Search

Aluminum nitride thin-film bulk wave resonant pressure sensors employing $c$- and tilted $c$-axis texture, have been fabricated and tested for their pressure sensitivities. The $c$-axis tilted film bulk acoustic resonators pressure sensors demonstrate substantially higher-pressure sensitivity compared to its $c$-axis oriented counterpart. More specifically, the thickness plate quasi-shear resonance has demonstrated the highest pressure sensitivity while further being able to

Emil Anderas; Ilia Katardjiev; Ventsislav M. Yantchev

2012-01-01

371

Toolbit Mounted Thin Film Zinc Oxide Sensors for Process Control in Lathe and Milling Machine Applications  

Microsoft Academic Search

Thin films (1.8 microns thick) of ZnO have been deposited on tungsten carbide tool inserts by rf diode sputtering. The goal is to use ZnO film as a sensor to monitor acoustic emission generated during cutting or t ool fracture. The sensor has detected resonances in the machine structure in the 100 Hz to 20 KHz range as well as

Brian Bischoff; S. Ramalingam; William P. Robbins

1987-01-01

372

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

373

Artificial neural networks and statistical pattern recognition improve MOSFET gas sensor array calibration  

Microsoft Academic Search

It is noted that the poor selectivity of many gas sensors is disadvantageous when individual gases are studied in gas mixtures or when odors are identified. It has been shown that pattern recognition methods are very promising when gases or odors are identified by means of gas sensor arrays. The quality of predictive models, based on partial least square (PLS),

H. Sundgren; F. Winquist; I. Lundstrom

1991-01-01

374

Multiparametric sensor based on DBR porous silicon for detection of ethanol gas  

Microsoft Academic Search

We are here concerned with fabrication possibility of multiparametric gas sensor based on porous silicon. In order to use the porous silicon as a gas sensor, we made the DBR (distributed Bragg reflector) porous silicon onto silicon wafer and monitored the change of three parameters during exposure of DBR porous silicon to ethanol gas. The sensing parameters were the shift

Han-Jung Kim; Young-You Kim; Ki-Won Lee

2010-01-01

375

Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts  

E-print Network

Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts E. Comini, G for publication 16 July 2002 Gas sensors have been fabricated using the single-crystalline SnO2 nanobelts of the gas, is 4160% for 250 ppm of ethanol and 1550% for 0.5 ppm NO2 at 400 °C. The results demonstrate

Wang, Zhong L.

376

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; Wllenstein, Jrgen

2011-06-01

377

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

378

Tools with built-in thin film thermocouple sensors for monitoring cutting temperature  

Microsoft Academic Search

The ability to monitor in real time, the thermal activation and thermal impact to cutting tools has been very appealing to the manufacturing industries. Such responses can be measured with appropriate sensors such as thin film thermocouples (TFTs) built in cutting tools. The challenges have been to instrument the tool, equipment and sensors, which can withstand high stress and temperature

Ali Basti; Toshiyuki Obikawa; Jun Shinozuka

2007-01-01

379

Development of nanostructured protective "sight glasses" for IR gas sensors  

NASA Astrophysics Data System (ADS)

In this work protective "sight glasses" for infrared gas sensors showing a sub-wavelength nanostructure with random patterns have been fabricated by reactive ion etching (RIE) in an easy and comparable cheap single step mask-less process. By an organic coating, the intrinsic water repellent property of the surface could be enhanced, shown by contact angle and roll-off angle measurements. The "self-cleaning" surface property and chemical robustness towards aggressive environments are demonstrated. FT-IR spectroscopy concerning the optical properties of these nanostructured silicon windows revealed a stable anti-reflective "moth-eye" effect in certain wavelength ranges owing to the nanostructures.

Bergmann, Ren; Davis, Zachary James; Schmidt, Michael Stenbk; Clausen, Snnik; Boisen, Anja; Jensen, Jens Mller; Buchner, Rainer; Stolberg-Rohr, Thomine; Jakobsen, Mogens Havsteen

2011-06-01

380

Identification of the dynamic properties of temperature-sensors in natural and petroleum gas  

Microsoft Academic Search

This paper presents a theoretical and experimental investigation of the dynamic properties of contact temperature-sensors in air as well as in natural and petroleum gas. Particularly with gas-supply systems, which can operate either with natural or petroleum gas, a knowledge of a sensors dynamic properties and sensitivity to different pressure and velocity conditions can be a crucial factor in the

Franc Cimerman; Bogdan Blagojevic; Ivan Bajsic

2002-01-01

381

Fabrication and ethanol sensing characteristics of ZnO nanowire gas sensors  

Microsoft Academic Search

Based on the achievement of synthesis of ZnO nanowires in mass production, ZnO nanowires gas sensors were fabricated with microelectromechanical system technology and ethanol-sensing characteristics were investigated. The sensor exhibited high sensitivity and fast response to ethanol gas at a work temperature of 300 C. Our results demonstrate the potential application of ZnO nanowires for fabricating highly sensitive gas sensors.

Q. Wan; Q. H. Li; Y. J. Chen; T. H. Wang; X. L. He; J. P. Li; C. L. Lin

2004-01-01

382

Deposition Of Thin-Film Sensors On Glass-Fiber/Epoxy Models  

NASA Technical Reports Server (NTRS)

Direct-deposition process devised for fabrication of thin-film sensors on three-dimensional, curved surfaces of models made of stainless steel covered with glass-fiber/epoxy-matrix composite material. Models used under cryogenic conditions, and sensors used to detect on-line transitions between laminar and turbulent flows in wind tunnel environments. Sensors fabricated by process used at temperatures from minus 300 degrees F to 175 degrees F.

Tran, Sang Q.

1995-01-01

383

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

384

Nanocomposite thin films for optical gas sensing  

SciTech Connect

The disclosure relates to a plasmon resonance-based method for gas sensing in a gas stream utilizing a gas sensing material. In an embodiment the gas stream has a temperature greater than about 500.degree. C. The gas sensing material is comprised of gold nanoparticles having an average nanoparticle diameter of less than about 100 nanometers dispersed in an inert matrix having a bandgap greater than or equal to 5 eV, and an oxygen ion conductivity less than approximately 10.sup.-7 S/cm at a temperature of 700.degree. C. Exemplary inert matrix materials include SiO.sub.2, Al.sub.2O.sub.3, and Si.sub.3N.sub.4 as well as modifications to modify the effective refractive indices through combinations and/or doping of such materials. Changes in the chemical composition of the gas stream are detected by changes in the plasmon resonance peak. The method disclosed offers significant advantage over active and reducible matrix materials typically utilized, such as yttria-stabilized zirconia (YSZ) or TiO.sub.2.

Ohodnicki, Paul R; Brown, Thomas D

2014-06-03

385

Multilayer silver / dielectric thin-film coated hollow waveguides for sensor and laser power delivery applications  

E-print Network

Multilayer silver / dielectric thin-film coated hollow waveguides for sensor and laser power thin film designs deposited on silver coated silica hollow waveguides have been used for low-loss transmission of infrared radiation in the 2 ­ 14 micrometer region. Silver iodide has traditionally been

386

An objective protocol for comparing the noise performance of silver halide film and digital sensor  

NASA Astrophysics Data System (ADS)

Digital sensors have obviously invaded the photography mass market. However, some photographers with very high expectancy still use silver halide film. Are they only nostalgic reluctant to technology or is there more than meets the eye? The answer is not so easy if we remark that, at the end of the golden age, films were actually scanned before development. Nowadays film users have adopted digital technology and scan their film to take advantage from digital processing afterwards. Therefore, it is legitimate to evaluate silver halide film "with a digital eye", with the assumption that processing can be applied as for a digital camera. The article will describe in details the operations we need to consider the film as a RAW digital sensor. In particular, we have to account for the film characteristic curve, the autocorrelation of the noise (related to film grain) and the sampling of the digital sensor (related to Bayer filter array). We also describe the protocol that was set, from shooting to scanning. We then present and interpret the results of sensor response, signal to noise ratio and dynamic range.

Cao, Frdric; Guichard, Frdric; Hornung, Herv; Tessire, Rgis

2012-01-01

387

High-performance gas sensors with temperature measurement  

PubMed Central

There are a number of gas ionization sensors using carbon nanotubes as cathode or anode. Unfortunately, their applications are greatly limited by their multi-valued sensitivity, one output value corresponding to several measured concentration values. Here we describe a triple-electrode structure featuring two electric fields with opposite directions, which enable us to overcome the multi-valued sensitivity problem at 1 atm in a wide range of gas concentrations. We used a carbon nanotube array as the first electrode, and the two electric fields between the upper and the lower interelectrode gaps were designed to extract positive ions generated in the upper gap, hence significantly reduced positive ion bombardment on the nanotube electrode, which allowed us to maintain a high electric field near the nanotube tips, leading to a single-valued sensitivity and a long nanotube life. We have demonstrated detection of various gases and simultaneously monitoring temperature, and a potential for applications. PMID:23405281

Zhang, Yong; Li, Shengtao; Zhang, Jingyuan; Pan, Zhigang; Min, Daomin; Li, Xin; Song, Xiaoping; Liu, Junhua

2013-01-01

388

Vapor pressures and gas-film coefficients for ketones  

USGS Publications Warehouse

Comparison of handbook vapor pressures for seven ketones with more recent literature data showed large differences for four of the ketones. Gas-film coefficients for the volatilization of these ketones from water determined by two different methods were in reasonable agreement. ?? 1987.

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

1987-01-01

389

Multiwalled carbon nanotube films as small-sized temperature sensors  

NASA Astrophysics Data System (ADS)

We present the fabrication of thick and dense carbon nanotube networks in the form of freestanding films (CNTFs) and the study of their electric resistance as a function of the temperature, from 4 to 420 K. A nonmetallic behavior with a monotonic R(T ) and a temperature coefficient of resistance around -710-4 K-1 is generally observed. A behavioral accordance of the CNTF conductance with the temperature measured by a solid-state thermistor (ZnNO, Si, or Pt) is demonstrated, suggesting the possibility of using CNTFs as temperature small-sized (freely scalable) sensors, besides being confirmed by a wide range of sensitivity, fast response, and good stability and durability. Concerning electric behavior, we also underline that a transition from nonmetal to metal slightly below 273 K has been rarely observed. A model involving regions of highly anisotropic metallic conduction separated by tunneling barrier regions can explain the nonmetallic to metallic crossover based on the competing mechanisms of the metallic resistance rise and the barrier resistance lowering.

Di Bartolomeo, A.; Sarno, M.; Giubileo, F.; Altavilla, C.; Iemmo, L.; Piano, S.; Bobba, F.; Longobardi, M.; Scarfato, A.; Sannino, D.; Cucolo, A. M.; Ciambelli, P.

2009-03-01

390

Breath acetone monitoring by portable Si:WO3 gas sensors  

PubMed Central

Breath analysis has the potential for early stage detection and monitoring of illnesses to drastically reduce the corresponding medical diagnostic costs and improve the quality of life of patients suffering from chronic illnesses. In particular, the detection of acetone in the human breath is promising for non-invasive diagnosis and painless monitoring of diabetes (no finger pricking). Here, a portable acetone sensor consisting of flame-deposited and in situ annealed, Si-doped epsilon-WO3 nanostructured films was developed. The chamber volume was miniaturized while reaction-limited and transport-limited gas flow rates were identified and sensing temperatures were optimized resulting in a low detection limit of acetone (~20 ppb) with short response (1015 s) and recovery times (3570 s). Furthermore, the sensor signal (response) was robust against variations of the exhaled breath flow rate facilitating application of these sensors at realistic relative humidities (8090%) as in the human breath. The acetone content in the breath of test persons was monitored continuously and compared to that of state-of-the-art proton transfer reaction mass spectrometry (PTR-MS). Such portable devices can accurately track breath acetone concentration to become an alternative to more elaborate breath analysis techniques. PMID:22790702

Righettoni, Marco; Tricoli, Antonio; Gass, Samuel; Schmid, Alex; Amann, Anton; Pratsinis, Sotiris E.

2013-01-01

391

Role of surface texturization on the gas-sensing properties of nanostructured porous silicon films  

NASA Astrophysics Data System (ADS)

In this work, by means of high-resolution X-ray diffraction, excitation ?-dependent photoluminescence (PL) and Fourier transform infrared studies, it has been demonstrated that hydrogen-passivated porous silicon (PS) films with high PL and stability can be obtained on p-type Si(1 0 0) substrate by simple texturization process rather than by resorting to any anodic, chemical or thermal oxidation of PS [T. Karacali, B. Cakmak, H. Efeoglu, Opt. Express 11 (2003) 1237]. PS formed on textured substrates is superior to PS formed on polished silicon substrates at the same current density and time of anodization. The application of PS films formed on textured substrate as a gas sensor has been demonstrated and it shows higher sensitivity values upon exposure to ethanol as compared with polished PS specimens of similar porosity. The improved properties are attributed to the formation of highly porous vertical layers separating macroscopic domains of nanoporous silicon.

Sharma, Shailesh N.; Bhagavannarayana, G.; Kumar, Umesh; Debnath, R.; Mohan, S. Chandra

2007-01-01

392

A comparison of chemical sensors based on the different ordered inverse opal films  

Microsoft Academic Search

The three different inverse opal films including polystyrene (PS), silicon dioxide (SiO2) and titanium dioxide (TiO2) inverse opal have been fabricated by the self-assembly colloidal crystal template technique. Based on the Bragg's law, these inverse opal films were used as chemical sensors chips to detect the different concentration of ethanol solutions. The optical sensing properties of three inverse opal films

Jianlin Li; Tiesong Zheng

2008-01-01

393

Room-Temperature Ammonia Sensor Based on CuxS Film  

Microsoft Academic Search

Gas sensing properties, surface chemical composition and morphology of CuxS-based films deposited on polyethylene and porous Si substrates were investigated. It was determined that the CuxS films show a reversible increase of resistance due to the exposure to ammonia gas at room temperature. The analysed samples were not sensitive to H2 and CO.

M. P. Casaletto; G. M. Ingo; S. Kaciulis; G. Mattogno; L. Pandolfi; A. Galdikas; A. Mironas; V. Strazdiene; I. Simkiene; A. Setkus; I. Ancutiene; V. Janickis

2000-01-01

394

Electro-thermal modeling of a microbridge gas sensor  

SciTech Connect

Fully CMOS-compatible, surface-micromachined polysilicon microbridges have been 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 comparing its simulated behavior with experiment. Temperature distribution of an electrically heated microbridges was measured using an infrared microscope. Comparisons among the measured distribution, the SPICE simulation, and distributions obtained by analytical methods show that heating at the ends of a microbridges has important implications for device response. Additional comparisons between measured and simulated current-voltage characteristics, as well as transient response, 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 microbridges gas sensor are 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, R.P.; Smith, J.H.; Ricco, A.J.; Hughes, R.C.; Moreno, D.J. [Sandia National Labs., Albuquerque, NM (United States); Huber, R.J. [Utah Univ., Salt Lake City, UT (United States). Dept. of Electrical Engineering

1997-08-01

395

Selective permeation of hydrogen gas using cellulose nanofibril film.  

PubMed

Biobased membranes that can selectively permeate hydrogen gas have been developed from aqueous dispersions of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCN) prepared from wood cellulose: TOCN-coated plastic films and self-standing TOCN films. Compared with TOCNs with sodium, lithium, potassium, and cesium carboxylate groups, TOCN with free carboxyl groups (TOCN-COOH) had much high and selective H2 gas permeation performance. Because permeabilities of H2, N2, O2, and CO2 gases through the membranes primarily depended on their kinetic diameters, the gas permeation behavior of the various TOCNs can be explained in terms of a diffusion mechanism. Thus, the selective H2 gas permeability for TOCN-COOH was probably due to a larger average size in free volume holes present between nanofibrils in the layer and film than those of other TOCNs with metal carboxylate groups. The obtained results indicate that TOCN-COOH membranes are applicable as biobased H2 gas separation membranes in fuel cell electric power generation systems. PMID:23594396

Fukuzumi, Hayaka; Fujisawa, Shuji; Saito, Tsuguyuki; Isogai, Akira

2013-05-13

396

Enhanced room temperature ozone response of SnO2 thin film sensor  

NASA Astrophysics Data System (ADS)

Room temperature responses of SnO2 thin film sensors were investigated for ozone detection. The SnO2 sensors were prepared using sol-gel process. Triton (X-100) surfactant was used as dispersant in the reaction system. The sensitive layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) after heat treatments at 300 C for 1 h. The effect of the dispersant on SnO2 thin film sensor surface was found to lead to an enhanced response of about 3.5 times for the detection of ozone (500 ppb) at room temperature. Results are concordant for indicating the possibility of utilizing the sensor based on SnO2 thin film for efficient detection of O3 at room temperature without activation using catalysts or UV radiations.

Belaqziz, Mohamed; Amjoud, M.'barek; Gaddari, Abdelhadi; Rhouta, Benassa; Mezzane, Daoud

2014-07-01

397

Fluorescent-dye-doped sol-gel sensor for highly sensitive carbon dioxide gas detection below atmospheric concentrations.  

PubMed

Optical fluorescence sol-gel sensors have been developed for the detection of carbon dioxide gas in the 0.03-30% range with a detection limit of 0.008% (or 80 ppm) and a quantitation limit of 0.02% (or 200 ppm) CO(2). Sol-gels were spin-coated on glass slides to create an organically modified silica-doped matrix with the 1-hydroxypyrene-3,6,8-trisulfonate (HPTS) fluorescent indicator. The luminescence intensity of the HPTS indicator (513 nm) is quenched by CO(2), which protonates the anionic form of HPTS. An ion pair technique was used to incorporate the lipophilic dye into the hydrophilic sol-gel matrix. TiO(2) particles (<5 microm diameter) were added to induce Mie scattering and increase the incident light interaction with the sensing film, thus increasing the signal-to-noise ratio. Moisture-proof overcoatings have been used to maintain a constant level of water inside the sensor films. The optical sensors are inexpensive to prepare and can be easily coupled to fiber optics for remote sensing capabilities. A fiber-optic bundle was used for the gas detection and shown to work as part of a multianalyte platform for simultaneous detection of multiple analytes. The studies reported here resulted in the development of sol-gel optical fluorescent sensors for CO(2) gas with sensitivity below that in the atmosphere (ca. 387 ppm). These sensors are a complementary approach to current FT-IR measurements for real-time carbon dioxide detection in environmental applications. PMID:20038093

Dansby-Sparks, Royce N; Jin, Jun; Mechery, Shelly J; Sampathkumaran, Uma; Owen, Thomas William; Yu, Bi Dan; Goswami, Kisholoy; Hong, Kunlun; Grant, Joseph; Xue, Zi-Ling

2010-01-15

398

Polyvinylidene fluoride film sensors in collocated feedback structural control: application for suppressing impact-induced disturbances.  

PubMed

Polyvinylidene fluoride (PVDF) films are light, flexible, and have high piezoelectricity. Because of these advantages, they have been widely used as sensors in applications such as underwater investigation, nondestructive damage detection, robotics, and active vibration suppression. PVDF sensors are especially preferred over conventional strain gauges in active vibration control because the PVDF sensors are easy to cut into different sizes or shapes as piezoelectric actuators and they can then be placed as collocated pairs. In this work, to focus on demonstrating the dynamic sensing performance of the PVDF film sensor, we revisit the active vibration control problem of a cantilever beam using a collocated lead zirconate titanate (PZT) actuator/PVDF film sensor pair. Before applying active vibration control, the measurement characteristics of the PVDF film sensor are studied by simultaneous comparison with a strain gauge. The loading effect of the piezoelectric actuator on the cantilever beam is also investigated in this paper. Finally, four simple, robust active vibration controllers are employed with the collocated PZT/PVDF pair to suppress vibration of the cantilever beam subjected to impact loadings. The four controllers are the velocity feedback controller, the integral resonant controller (IRC), the resonant controller, and the positive position feedback (PPF) controller. Suppression of impact disturbances is especially suitable for the purpose of demonstrating the dynamic sensing performance of the PVDF sensor. The experimental results also provide suggestions for choosing between the previously mentioned controllers, which have been proven to be effective in suppressing impact-induced vibrations. PMID:23443690

Ma, Chien-Ching; Chuang, Kuo-Chih; Pan, Shan-Ying

2011-12-01

399

Gas permeability measurements for film envelope materials  

DOEpatents

Method and apparatus for measuring the permeability of polymer film materials such as used in super-insulation powder-filled evacuated panels (PEPs) reduce the time required for testing from several years to weeks or months. The method involves substitution of a solid non-outgassing body having a free volume of between 0% and 25% of its total volume for the usual powder in the PEP to control the free volume of the ``body-filled panel.`` Pressure versus time data for the test piece permit extrapolation to obtain long term performance of the candidate materials. 4 figs.

Ludtka, G.M.; Kollie, T.G.; Watkin, D.C.; Walton, D.G.

1998-05-12

400

Gas permeability measurements for film envelope materials  

DOEpatents

Method and apparatus for measuring the permeability of polymer film materials such as used in super-insulation powder-filled evacuated panels (PEPs) reduce the time required for testing from several years to weeks or months. The method involves substitution of a solid non-outgassing body having a free volume of between 0% and 25% of its total volume for the usual powder in the PEP to control the free volume of the "body-filled panel". Pressure versus time data for the test piece permit extrapolation to obtain long term performance of the candidate materials.

Ludtka, Gerard M. (Oak Ridge, TN); Kollie, Thomas G. (Oak Ridge, TN); Watkin, David C. (Clinton, TN); Walton, David G. (Knoxville, TN)

1998-01-01

401

Optical sensor based on the surface plasmon resonance phenomenon in a thin gold film  

NASA Astrophysics Data System (ADS)

The work is devoted to investigations of physical and chemical processes taking place at the boundary between a thin gold film subjected to low-temperature annealing and gas or liquid media. Besides, the work is aimed to research formation of protective, stabilizing and orienting ones in optimization of characteristics inherent to biochemical sensors based on the effect of optical excitation of the surface electromagnetic wave in the thin gold film as well as in investigations of the reflection angular function when using the mode of attenuated internal total reflection. Shown is the necessity to apply the procedure of 120C temperature annealing that can result in smoothing a small-scale relief of the gold surface and obtaining some optimal parameters of a resonance curve as well as in formation of defectless protective and stabilizing nano-dimensional layers. To protect gold surface, studied are several mechanisms of layer formation in the cases of gold thiolate and gold sulfide. The way of oriented fixation of a sensitive molecular layer using the non-organic cooper aminopentacyanoferrate layer is worked out.

Kostyukevych, Kateryna V.; Shirshov, Yuri M.

2003-08-01

402

Development of a Prototype Optical Hydrogen Gas Sensor Using a Getter-Doped Polymer Transducer for Monitoring Cumulative Exposure: Preliminary Results  

SciTech Connect

A novel prototype optical sensor for monitoring cumulative hydrogen gas exposure was fabricated and evaluated. Chemical-to-optical transduction was accomplished by detecting the intensity of 670 nm laser light transmitted through a hydrogen getter-doped polymer film mounted at the end of an optical fiber; the transmittance of the composite film increased with uptake of hydrogen by the embedded getter. The composite film consisted of the hydrogen getter 1,4-bis(phenylethynyl)benzene, also known as DEB, with carbon-supported palladium catalyst embedded in silicone elastomer. Because the change in transmittance was irreversible and occurred continuously as the getter captured hydrogen, the sensor behaved like a dosimeter, providing a unique indication of the cumulative gas exposure.

Small IV, W; Maitland, D J; Wilson, T S; Bearinger, J P; Letts, S A; Trebes, J E

2008-06-05

403

Optical sensor for carbon dioxide gas determination, characterization and improvements.  

PubMed

A study of different alternatives to improve the stability and lifetime of sensors for the determination of gaseous CO2 has been performed. It includes the characterization of different sensing membranes, a discussion of the results obtained and possibilities for the future. The solid sensor membrane for gaseous CO2 based on changes in the luminiscence of a luminophore immobilized on O2-insensitive film, concurrent with the displacement of a pH indicator, has some drawbacks, such as the loss of efficiency over time and the need to maintain the sensor in special atmospheric conditions. As a solution to these drawbacks, two alternatives were tested, the first alternative was replacing the newly proposed tetraoctyl ammonium hydroxide (TOAOH ) phase transfer agent with other basic agents that did not undergo a Hoffman degradation reaction, and the second alternative was the use of hydrophilic polymers that could retain water needed for CO2 sensing more efficiently. The different membranes tested indicated that the use of tetramethyl ammonium (TMAOH) instead of TOAOH as the phase transfer agent produced better results regarding stability and sensitivity. In addition, replacing the membrane polymer with hydrophilic polymers improved the sensing characteristics in terms of response time and stability over hydrophobic polymers. With a detection limit of 0.006%, the response time is 19s and the recovery time is 100s. The lifetime of the sensing membranes, which do not need to be held in any special atmosphere other than darkness, is longer than at least 300 days for membranes with TMAOH in hydrophilic polymer and 515 days for membranes with TMAOH in ethyl cellulose. PMID:24881553

Aguayo-Lpez, M L; Capitn-Vallvey, L F; Fernndez-Ramos, M D

2014-08-01

404

Thin Film Ceramic Strain Sensor Development for Harsh Environments: Interim Report on 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 Glenn 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 can be on aircraft hot section structures and on thermal protection systems. The near-term interim goal of the 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 and physical compatibility with our microfabrication procedures and substrates.

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

2006-01-01

405

Electrical properties and microstructure of tin dioxide thin films deposited by pulsed laser ablation for gas sensing applications  

NASA Astrophysics Data System (ADS)

Despite the widespread use of solid state semiconductor oxide gas sensors in many applications, the basic principles of operation and fabrication are still not well understood. Thin film sensors hold many promises due to advances in thin film fabrication and integration to existing silicon microtechnology. This thesis focused on understanding structure-property relationships of thin SnO2 films with customized microstructures and chemistries to improve fundamental sensor science. We used surface templates and femtosecond pulsed laser ablation to grow SnO2 with tailored microstructures and thickness. This system allowed the growth of high quality epitaxial single crystals, nanodomain epitaxial crystals and randomly oriented polycrystals. The electrical properties were very dependent on the film thickness due to interaction of charge carriers with the surface/interface and to a greater extent of film depleted of electrons from surface charge. Electron concentration was reduced by trapping at grain boundaries and planar defects. Grain boundary scattering and potential reduced the electron mobility in thin films. The gas sensing properties of thin films was improved as the film thickness decreased. Active grain boundaries in polycrystalline films resulted in a significant improvement of sensing properties over single crystal films. We also investigated the properties of donor and acceptor doped single crystal and polycrystalline materials. Donor dopants were mainly electronically compensated and resulted in near degenerate electron conduction in the films. Acceptor dopants were ionically compensated and decreased the electron concentration in the films. A trend of decreasing electron concentration with increasing acceptor dopant radius was found. Acceptor dopants in nanocrystalline films tended to show non-uniform distribution near the grain boundaries. The amount of segregation was dependent on ionic radius, grain size and native ionic space charge in the films. The sensing properties of the films were improved by the introduction of acceptor dopants whereas for donor dopants the response to gases was decreased with respect to undoped film. The sensitivity was directly proportional to the resistance with different maxima at different film thickness. Some dopants affected not only the electronic but also the chemical properties of the material. Epitaxial SnO2 and TiO2 heterolayers were studied as gas sensors. It was possible to grow high quality multilayers via pulsed laser deposition. The electronic properties of the resulting film could be tailored by changing the thickness and number of intercalating layers. The interfacial charge from misfit dislocations and bandgap misfit between the layers created n/N junctions that modulated the electron concentration. Non-linear I-V characteristics were measured across an epitaxial SnO2/TiO 2 bilayer. The heterostructures showed weak response to gases, although provide proof of principle of their potential usefulness.

Dominguez, Juan Eduardo

406

Self-activated ultrahigh chemosensitivity of oxide thin film nanostructures for transparent sensors  

PubMed Central

One of the top design priorities for semiconductor chemical sensors is developing simple, low-cost, sensitive and reliable sensors to be built in handheld devices. However, the need to implement heating elements in sensor devices, and the resulting high power consumption, remains a major obstacle for the realization of miniaturized and integrated chemoresistive thin film sensors based on metal oxides. Here we demonstrate structurally simple but extremely efficient all oxide chemoresistive sensors with ~90% transmittance at visible wavelengths. Highly effective self-activation in anisotropically self-assembled nanocolumnar tungsten oxide thin films on glass substrate with indium-tin oxide electrodes enables ultrahigh response to nitrogen dioxide and volatile organic compounds with detection limits down to parts per trillion levels and power consumption less than 0.2 microwatts. Beyond the sensing performance, high transparency at visible wavelengths creates opportunities for their use in transparent electronic circuitry and optoelectronic devices with avenues for further functional convergence. PMID:22905319

Moon, Hi Gyu; Shim, Young-Soek; Kim, Do Hong; Jeong, Hu Young; Jeong, Myoungho; Jung, Joo Young; Han, Seung Min; Kim, Jong Kyu; Kim, Jin-Sang; Park, Hyung-Ho; Lee, Jong-Heun; Tuller, Harry L.; Yoon, Seok-Jin; Jang, Ho Won

2012-01-01

407

The effect of multiwalled carbon nanotube doping on the CO gas sensitivity of TiO2 xerogel composite film  

NASA Astrophysics Data System (ADS)

A simple sol-gel method was applied for the synthesis of 0.01 wt% multiwalled carbon nanotubes (MWCNTs)-doped TiO2 xerogel composite film. The film's CO gas sensing properties were then evaluated. Doped MWCNTs were coated with TiO2 and distributed on a TiO2 xerogel matrix. The TiO2 xerogel showed an anatase structure after heat treatment at 450 C under vacuum. The specific surface area of the composite material was larger than the pure TiO2 xerogel material. The CO gas sensitivity of the MWCNTs(0.01 wt%)-doped TiO2 xerogel composite film was found to be seven times higher than that of pure TiO2 xerogel film and to have good stability. This higher gas-sensing property of the composite film was due to both an increase of specific surface area and the n-p junction structure of the TiO2 xerogel coated on MWCNTs. The electrons generated from TiO2 after adsorption of CO gas induces electron transfer from the TiO2 to the MWCNTs. This induces a characteristic change in the MWCNTs from p-type to n-type, and the resistance of MWCNTs-doped TiO2 xerogel composite sensor is therefore decreased.

Lee, Jin-Seok; Ha, Tae-Jung; Hong, Min-Hee; Park, Chang-Sun; Park, Hyung-Ho

2013-03-01

408

Dynamic coupling correlation of gas film in dry gas seal with spiral groove  

NASA Astrophysics Data System (ADS)

In working state, the dynamic performance of dry gas seal, generated by the rotating end face with spiral grooves, is determined by the open force of gas film and leakage flow rate. Generally, the open force and the leakage flow rate can be obtained by finite element method, computational fluid dynamics method and experimental measurement method. However, it will take much time to carry out the above measurements and calculations. In this paper, the approximate model of parallel grooves based on the narrow groove theory is used to establish the dynamic equations of the gas film for the purpose of obtaining the dynamic parameters of gas film. The nonlinear differential equations of gas film model are solved by Runge-Kutta method and shooting method. The numerical values of the pressure profiles, leakage flux and opening force on the seal surface are integrated, and then compared to experimental data for the reliability of the numerical simulation. The results show that the numerical simulation curves are in good agreement with experimental values. Furthermore, the opening force and the leakage flux are proved to be strongly correlated with the operating parameters. Then, the function-coupling method is introduced to analyze the numerical results to obtain the correlation formulae of the opening force and leakage flux respectively with the operating parameters, i.e., the inlet pressure and the rotating speed. This study intends to provide an effective way to predict the aerodynamic performance for designing and optimizing the groove styles in dry gas seal rapidly and accurately.

Liu, Zhengxian; Wang, Musu; Zhou, Yue; Wu, Ningning

2014-07-01

409

FAST TRACK COMMUNICATION: Effects of reducing interferers in a binary gas mixture on NO2 gas adsorption using carbon nanotube networked films based chemiresistors  

NASA Astrophysics Data System (ADS)

Analysis of binary gas mixtures using chemiresistors based on carbon nanotubes (CNTs) networked films has been performed for chemical detection up to a sub-ppm level. The effects of individual interfering analytes of reducing H2S and NH3 gases on oxidizing NO2 gas adsorption in CNTs tangled films are considered. The CNTs are grown by plasma-enhanced chemical vapour deposition technology onto inexpensive alumina substrates, coated by cobalt nanosized catalyst. Charge transfer between adsorbed gas molecules and CNT networks, characterized by a semiconducting p-type electrical transport, occurs depending on opposite trend in the sensor response to the electron-donating interfering gases (H2S, NH3) and target electron-withdrawing NO2 gas causing a compensation of the charge transport, upon given working conditions. This compensated exchange of electrical charge affects the limit of detection of the targeted NO2 gas sensed in different real-world binary gas mixtures of reducing interferers of H2S and NH3. In addition, the functionalization of the CNT films with Au nanoclusters enhanced the sensitivity of the chemiresistor and tuned the compensation of electrical charge crossover in the selected binary oxido-reducing mixtures.

Penza, M.; Rossi, R.; Alvisi, M.; Signore, M. A.; Serra, E.

2009-04-01

410

Multicomponent analysis of alcohol vapors using integrated gas chromatography with sensor arrays  

Microsoft Academic Search

We have fabricated and tested a multiarray polymer sensor by integrating the sensor array with a gas chromatograph. We compared the performance of the system with a contemporary thermoconductivity detector for the identification and detection of different volatile organic compounds (VOCs). These sensor arrays were not only able to detect the different compounds but also demonstrated a very wide linear

Adam K. Wanekaya; Michiko Uematsu; Marc Breimer; Omowunmi A. Sadik

2005-01-01

411

Fiber optic gas sensors with vanadium oxide and tungsten oxide nanoparticle coated claddings  

NASA Astrophysics Data System (ADS)

Fiber optic gas sensors with nanoparticles of V2O5 and WO3 as the cladding of a PMMA fiber have been proposed in this work. The spectral response of these sensors for detection of ammonia, methanol and ethanol under various concentrations has been studied at room temperature. The time response characteristics of the sensors are also presented.

Renganathan, B.; Sastikumar, D.; Raj, S. Gokul; Ganesan, A. R.

2014-03-01

412

Isotropic and anisotropic dipeptide films based on gas phase deposition  

NASA Astrophysics Data System (ADS)

We demonstrated the fabrication and application of well-ordered and vertically aligned dipeptide nanostructures based on a simple gas phase deposition. Deposited nanostructures exhibited the superhydrophobic property with a very low sliding angle. Highly reproducible SERS data have also been obtained after combining deposited films with a thin layer of gold. In addition to these, directional peptide films were, for the first time, successfully fabricated based on the oblique angle deposition technique. We believe that such bio-inspired materials would have a great impact in several technological applications involving catalysis, tissue engineering and biosensors.

Demirel, Gokhan; Tamer, Ugur

2012-06-01

413

A novel nanometric DNA thin film as a sensor for alpha radiation  

PubMed Central

The unexpected nuclear accidents have provided a challenge for scientists and engineers to develop sensitive detectors, especially for alpha radiation. Due to the high linear energy transfer value, sensors designed to detect such radiation require placement in close proximity to the radiation source. Here we report the morphological changes and optical responses of artificially designed DNA thin films in response to exposure to alpha radiation as observed by an atomic force microscope, a Raman and a reflectance spectroscopes. In addition, we discuss the feasibility of a DNA thin film as a radiation sensing material. The effect of alpha radiation exposure on the DNA thin film was evaluated as a function of distance from an 241Am source and exposure time. Significant reflected intensity changes of the exposed DNA thin film suggest that a thin film made of biomolecules can be one of promising candidates for the development of online radiation sensors. PMID:23792924

Kulkarni, Atul; Kim, Byeonghoon; Dugasani, Sreekantha Reddy; Joshirao, Pranav; Kim, Jang Ah; Vyas, Chirag; Manchanda, Vijay; Kim, Taesung; Park, Sung Ha

2013-01-01

414

A novel nanometric DNA thin film as a sensor for alpha radiation  

NASA Astrophysics Data System (ADS)

The unexpected nuclear accidents have provided a challenge for scientists and engineers to develop sensitive detectors, especially for alpha radiation. Due to the high linear energy transfer value, sensors designed to detect such radiation require placement in close proximity to the radiation source. Here we report the morphological changes and optical responses of artificially designed DNA thin films in response to exposure to alpha radiation as observed by an atomic force microscope, a Raman and a reflectance spectroscopes. In addition, we discuss the feasibility of a DNA thin film as a radiation sensing material. The effect of alpha radiation exposure on the DNA thin film was evaluated as a function of distance from an 241Am source and exposure time. Significant reflected intensity changes of the exposed DNA thin film suggest that a thin film made of biomolecules can be one of promising candidates for the development of online radiation sensors.

Kulkarni, Atul; Kim, Byeonghoon; Dugasani, Sreekantha Reddy; Joshirao, Pranav; Kim, Jang Ah; Vyas, Chirag; Manchanda, Vijay; Kim, Taesung; Park, Sung Ha

2013-06-01

415

Air Monitoring System in Elders' Apartment with QCM Type Gas Sensors  

NASA Astrophysics Data System (ADS)

The gas monitoring system for elders' apartment using QCM sensors was newly developed. The QCM sensors for sulfide gas and ammonia gas were used for this system. The system for bodily wastes was fabricated and applied to nursing care system in elders' apartment. This system is composed by the sensor unit, communication unit and data server. Care person can see whether the linen should be changed or not without seeing over each room. The QCM sensors have some problems such as the interference of humidity and temperature, therefore these influences were dissolved using humidity sensor and temperature sensor as feedback source. The sensors were placed in several points of elders' apartment for 2 weeks. This system can be used in elders' apartment successfully.

Kikuchi, Masashi; Ito, Tsukasa; Shiratori, Seimei

416

Effects of textural properties on the response of a SnO2-based gas sensor for the detection of chemical warfare agents.  

PubMed

The sensing behavior of SnO(2)-based thick film gas sensors in a flow system in the presence of a very low concentration (ppb level) of chemical agent simulants such as acetonitrile, dipropylene glycol methyl ether (DPGME), dimethyl methylphosphonate (DMMP), and dichloromethane (DCM) was investigated. Commercial SnO(2) [SnO(2)(C)] and nano-SnO(2) prepared by the precipitation method [SnO(2)(P)] were used to prepare the SnO(2) sensor in this study. In the case of DCM and acetonitrile, the SnO(2)(P) sensor showed higher sensor response as compared with the SnO(2)(C) sensors. In the case of DMMP and DPGME, however, the SnO(2)(C) sensor showed higher responses than those of the SnO(2)(P) sensors. In particular, the response of the SnO(2)(P) sensor increased as the calcination temperature increased from 400 C to 800 C. These results can be explained by the fact that the response of the SnO(2)-based gas sensor depends on the textural properties of tin oxide and the molecular size of the chemical agent simulant in the detection of the simulant gases (0.1-0.5 ppm). PMID:22163991

Lee, Soo Chool; Kim, Seong Yeol; Lee, Woo Suk; Jung, Suk Yong; Hwang, Byung Wook; Ragupathy, Dhanusuraman; Lee, Duk Dong; Lee, Sang Yeon; Kim, Jae Chang

2011-01-01

417

An industrial sensor for reliable ice detection in gas turbines  

SciTech Connect

Ice formation in the intake duct and compressor blading is a constant risk on gas turbines operating in regions where there are unfavorable ambient conditions. If allowed to continue there is a clear danger that pieces of ice will be ingested by the machine causing substantial damage. To protect the machine from possible damage, if ice is suspected by the operator the de-icing system is activated, injecting hot bleed air from the last compressor stages into the cold inlet air, naturally causing a decrease in power and efficiency. There exists a requirement for an ice detection system which will reliably detect the presence of ice and therefore optimize the use of bleed air for de-icing and reduce unnecessary power and efficiency losses. This paper discusses the necessary conditions for icing and describes a robust industrial sensor for reliable ice detection. The system, which is suitable for ground based gas turbines, has been installed on a 130MW gas turbine in Holland for the last three years and some of the results are presented here together with the economic advantages to be gained from installing such a system.

Freestone, J.W.; Weber, M. [Vibro-Meter SA, Fribourg (Switzerland). Dept. of Machinery Monitoring and Diagnostics

1994-12-31

418

Fabrication of a Miniaturized Room Temperature Ionic Liquid Gas Sensor for Human Health and  

E-print Network

pollutants on human health and safety has escalated the demand for sensors to monitor hazardous gases. Room, low power, multi-gas monitoring systems suitable for individuals to wear and capable of constantlyFabrication of a Miniaturized Room Temperature Ionic Liquid Gas Sensor for Human Health and Safety

Mason, Andrew

419

Gas Sensors Arrays (Electronic Noses): a study about the speed\\/accuracy ratio  

Microsoft Academic Search

New Fingerprint Mass Spectra (FMS) systems claim for a higher precision, a reduced analysis time, and a lower drift, compared with Gas Sensors Arrays Electronic Noses. We demonstrated in this study that metal oxide gas sensors may have highly improved performances for both accuracy and run time, when used in optimum conditions. The different noise components were quantified referring to

Patrick Mielle; Florence Marquis

2000-01-01

420

Gas sensor array based on surface acoustic wave devices for vapors detection and analysis  

Microsoft Academic Search

We have developed a new electronic nose based on a gas sensor array to detect organic vapors. The gas sensor array is based on 22 non-continuously working oscillators equipped with differently polymer-coated surface acoustic wave (SAW) sensors. The SAW detection system which is employed to detect various organic molecules in a static system was prepared using 99.8 MHz two-port SAW

Da-Jeng Yao; Hsu-Chao Hao; Mei-Ching Chen; Je-Shin Chao

2010-01-01

421

Taxonomy of Wireless Sensor Network Cyber Security Attacks in the Oil and Gas Industries  

Microsoft Academic Search

The monitoring of oil and gas plants using sensors allows for greater insight into safety and operational performance. However, as a result of strict installation regulations of powered sensors near oil and gas fittings, the introduction of new wired sensors to optimize end-of-lifecycle plants has been expensive, complex and time consuming. Recent advances in wireless technology have enabled low-cost Wireless

Pedram Radmand; Alex Talevski; Stig Petersen; Simon Carlsen

2010-01-01

422

Zero temperature coefficient gas-sealed pressure sensor using mechanical temperature compensation  

Microsoft Academic Search

A novel gas sealed capacitive pressure sensor with a self-temperature compensated structure is reported. The pressure sensor is sealed by Au-Au diffusion bonding in nitrogen with a pressure of 100 kPa and integrated with a platinum resistor based temperature sensor for human activity monitoring. A ring-shaped structure on the diaphragm of the pressure sensor is used for temperature compensation. The

X. C. Hao; Y. G. Jiang; H. Takao; K. Maenaka; T. Fujita; K. Higuchi

2011-01-01

423

Integrated CNT sensors in polymer microchannel for gas-flow shear-stress measurement  

Microsoft Academic Search

We have developed CNT sensors for gas-flow shear stress measurement inside a polymethylmethacrylate (PMMA) microchannel. An array of sensors is fabricated by using dielectrophoretic (DEP) technique to manipulate bundled single-walled carbon nanotubes (SWNTs) across the gold microelectrodes on a PMMA substrate. The sensors are then integrated in a PMMA microchannel, which is fabricated by SU-8 molding\\/hot-embossing technique. Since the sensors

Winnie W. Y. Chow; Wen J. Li; Steve C. H. Tung

2008-01-01

424

A New Low-Cost Electronic System to Manage Resistive Sensors for Gas Detection  

Microsoft Academic Search

In this paper, a new electronic system for gas detection is presented. Particular attention is focused on electronic noses that employ several resistive sensors. New resistive sensors may have high value due to new substances (TiO2) or to low-cost fabrication process and, supposing to use these sensors together with traditional ones (SnO2), a novel instrument to manage high-value resistive sensors

Alessandro Depari; Matteo Falasconi; Alessandra Flammini; Daniele Marioli; Stefano Rosa; Giorgio Sberveglieri; Andrea Taroni

2007-01-01

425

Laser Spectroscopic Trace-Gas Sensor Networks for Atmospheric Monitoring Applications  

Microsoft Academic Search

Laser-based atmospheric trace-gas sensors have great potential for long-term, real-time, maintenance free environmental monitoring in distributed Wireless Sensor Networks (WSN). We are developing a laser based chemical sensing technology with wide-area autonomous wireless sensor networking as the final target. Our prototype sensor measures atmospheric oxygen concentration in the form of a battery powered, handheld unit with power consumption <0.3W, sensitivity

Ardalan Amiri Sani; Lin Zhong; Frank Tittel; Gerard Wysocki

2009-01-01

426

Langasite surface acoustic wave gas sensors: modeling and verification.  

PubMed

We report finite element simulations of the effect of conductive sensing layers on the surface wave velocity of langasite substrates. The simulations include both the mechanical and electrical influences of the conducting sensing layer. We show that three-dimensional simulations are necessary because of the out-of-plane displacements of the commonly used (0, 138.5, 26.7) Euler angle. Measurements of the transducer input admittance in reflective delay-line devices yield a value for the electromechanical coupling coefficient that is in good agreement with the three-dimensional simulations on bare langasite substrate. The input admittance measurements also show evidence of excitation of an additional wave mode and excess loss resulting from the finger resistance. The results of these simulations and measurements will be useful in the design of surface acoustic wave gas sensors. PMID:23475923

Zheng, Peng; Greve, David W; Oppenheim, Irving J

2013-03-01

427

Fiber optic speed sensor for advanced gas turbine engine control  

NASA Astrophysics Data System (ADS)

A fiber optic speed sensor (FOSS) has been developed, bench tested and rig tested in a real turbine airflow environment. The FOSS employs an innovative design using a pressure tube and fiber optic microbend transducer in order to capture turbine blade pass wake frequency. The blade pass frequency can be converted by a signal processor into turbine rotational speed. The FOSS offers unique potential to meet future requirements for performance (0 to 25 KHz) and environmental tolerance (1200 F temperatures and EMI/EMP threats). Future efforts include development of the signal processor and environmental/durability testing focused on developing reliable, long life operation in the hostile environment of an advanced gas turbine engine.

Varshneya, Deepak; Maida, John L., Jr.; Overstreet, Mark A.

1991-02-01

428

Analysis of face deformation effects on gas film seal performance  

NASA Technical Reports Server (NTRS)

Analyses are presented for compressible fluid flow across shaft face seals with face deformation. The solutions are obtained from an approximate integral analysis. The models, used in this analysis, can predict gas film seal behavior operating at subsonic or choked flow conditions. The flow regime can either be laminar or turbulent. Entrance losses can also be accounted for. When fluid inertia effects are negligible and the sealing faces are slightly deformed, the following results are found for both laminar and turbulent flows: (1) The pressure profiles are independent of fluid properties; and (2) the parallel film leakage equation can be used, provided a characteristic film thickness is used. Pressure profiles are presented for both divergent and convergent seal faces under choked flow conditions.

Zuk, J.

1972-01-01

429

TiO2-based gas sensor: a possible application to SO2.  

PubMed

Fixation of SO2 molecules on anatase TiO2 surfaces with defects have been investigated by first-principles density functional theory (DFT) calculations and in situ Fourier transform infrared (FTIR) surface spectroscopy on porous TiO2 films. Intrinsic oxygen-vacancy defects, which are formed on TiO2(001) and TiO2(101) surfaces by ultraviolet (UV) light irradiation and at elevated temperatures, are found to be most effective in anchoring the SO2 gas molecules to the TiO2 surfaces. Both TiO2(101) and TiO2(001) surfaces with oxygen vacancies are found to exhibit higher SO2 adsorption energies in the DFT calculations. The adsorption mechanism of SO2 is explained on the basis of electronic structure, charge transfer between the molecule and the surface, and the oxidation state of the adsorbed molecule. The theoretical findings are corroborated by FTIR experiments. Moreover, the (001) surface with oxygen vacancies is found to bind SO2 gas molecules more strongly, as compared to the (101) surface. Higher concentration of oxygen vacancies on the TiO2 surfaces is found to significantly increase the adsorption energy. The results shed new insight into the sensing properties of TiO2-based gas sensors. PMID:23915321

Nisar, Jawad; Topalian, Zareh; De Sarkar, Abir; sterlund, Lars; Ahuja, Rajeev

2013-09-11

430

Thin-Film Magnetic-Field-Response Fluid-Level Sensor for Non-Viscous Fluids  

NASA Technical Reports Server (NTRS)

An innovative method has been developed for acquiring fluid-level measurements. This method eliminates the need for the fluid-level sensor to have a physical connection to a power source or to data acquisition equipment. The complete system consists of a lightweight, thin-film magnetic-field-response fluid-level sensor (see Figure 1) and a magnetic field response recorder that was described in Magnetic-Field-Response Measurement-Acquisition System (LAR-16908-1), NASA Tech Briefs, Vol. 30, No. 6 (June 2006), page 28. The sensor circuit is a capacitor connected to an inductor. The response recorder powers the sensor using a series of oscillating magnetic fields. Once electrically active, the sensor responds with its own harmonic magnetic field. The sensor will oscillate at its resonant electrical frequency, which is dependent upon the capacitance and inductance values of the circuit.

Woodard, Stanley E.; Shams, Qamar A.; Fox, Robert L.; Taylor, Bryant D.

2008-01-01

431

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

NASA Technical Reports Server (NTRS)

A study has been made of platinum thin films for application as high temperature resistive sensors. To support NASA Glenn Research Center s high temperature thin film sensor effort, a magnetron sputtering system was installed recently in the GRC Microsystems Fabrication Clean Room Facility. Several samples of platinum films were prepared using various system parameters to establish run conditions. These films were characterized with the intended application of being used as resistive sensing elements, either for temperature or strain measurement. The resistances of several patterned sensors were monitored to document the effect of changes in parameters of deposition and annealing. The parameters were optimized for uniformity and intrinsic strain. The evaporation of platinum via oxidation during annealing over 900 C was documented, and a model for the process developed. The film adhesion was explored on films annealed to 1000 C with various bondcoats on fused quartz and alumina. From this compiled data, a list of optimal parameters and characteristics determined for patterned platinum thin films is given.

Wrbanek, John D.; Laster, Kimala L. H.

2005-01-01

432

Temperature-dependent fiber optic hydrogen gas sensor response characteristics  

NASA Astrophysics Data System (ADS)

Dynamic response characteristics of silica fiber long-period grating with a modified cladding, composed of ~10-100 nm nanoparticle palladium oxides thin film material prepared by a magnetron sputtering technique, have been investigated at several elevated temperatures with a 2%H2/98%N II mixing gas concentration. The fiber cladding modified grating, without cladding chemical etching process, demonstrates 540 pm per 1% H II sensitivity, a better than 1sec response times at 160 C, respectively. The thermal responses of the prototype have demonstrated increased dynamic wavelength shift while reducing response time simultaneously. The observed thermal dependence of the prototype could be attributed to a combined effect of thermal dependent hydrogen atoms diffusion rate and hydrogen atoms solubility.

Xia, Hua; Deng, Kung-Li; Bousman, Ken; Wu, Juntao; Lee, Boon; Guida, Renato; McCarthy, Kevin

2006-08-01

433

Development of a thick film PZT foil sensor for use in structural health monitoring applications.  

PubMed

Acoustic emission (AE) monitoring is a technique of growing interest in the field of nondestructive testing (NDT). The use of AE devices to monitor the health of structural components is currently limited by the cost of AE equipment, which prohibits the permanent placement of AE devices on structures for the purposes of continuous monitoring and the monitoring of areas with limited access. Micro electromechanical systems (MEMS) can provide solutions to these problems. We present the manufacture of a 4.4-?m-thick lead zirconate titanate (PZT) film on a 110-?m-thick titanium foil substrate for use as an AE sensor. The thick-film sensor is benchmarked against commercially available AE sensors in static and dynamic monitoring applications. The thick-film AE device is found to perform well in the detection of AE in static applications. A low signal-to-noise ratio is found to prohibit the detection of AE in a dynamic application. PMID:23357911

Pickwell, Andrew J; Dorey, Robert A; Mba, David

2013-02-01

434

Scalable fabrication of SnO2 thin films sensitized with CuO islands for enhanced H2S gas sensing performance  

NASA Astrophysics Data System (ADS)

The detection of H2S, an important gaseous molecule that has been recently marked as a highly toxic environmental pollutant, has attracted increasing attention. We fabricate a wafer-scale SnO2 thin film sensitized with CuO islands using microelectronic technology for the improved detection of the highly toxic H2S gas. The SnO2-CuO island sensor exhibits significantly enhanced H2S gas response and reduced operating temperature. The thickness of CuO islands strongly influences H2S sensing characteristics, and the highest H2S gas response is observed with 20 nm-thick CuO islands. The response value (Ra/Rg) of the SnO2-CuO island sensor to 5 ppm H2S is as high as 128 at 200 C and increases nearly 55-fold compared with that of the bare SnO2 thin film sensor. Meanwhile, the response of the SnO2-CuO island sensor to H2 (250 ppm), NH3 (250 ppm), CO (250 ppm), and LPG (1000 ppm) are low (1.3-2.5). The enhanced gas response and selectivity of the SnO2-CuO island sensor to H2S gas is explained by the sensitizing effect of CuO islands and the extension of electron depletion regions because of the formation of p-n junctions.

Van Toan, Nguyen; Chien, Nguyen Viet; Van Duy, Nguyen; Vuong, Dang Duc; Lam, Nguyen Huu; Hoa, Nguyen Duc; Van Hieu, Nguyen; Chien, Nguyen Duc

2015-01-01

435

The role of oxygen in hydrogen sensing by a platinum-gate silicon carbide gas sensor: An ultrahigh vacuum study  

E-print Network

The role of oxygen in hydrogen sensing by a platinum-gate silicon carbide gas sensor: An ultrahigh of oxygen in hydrogen sensing by a platinum-gate silicon carbide gas sensor: An ultrahigh vacuum study Yung that elucidate the role of oxygen in the functioning of silicon carbide field-effect gas sensors with nonporous

Ghosh, Ruby N.

436

Research sensors  

NASA Technical Reports Server (NTRS)

The program described covers development of sensors and sensing techniques for research applications on aeropropulsion systems. In general, the sensors are used in-situ to measure the environment at a given location within a turbine engine, or to measure the response of an engine component to the imposed environment. Locations of concern are generally in the gas path and, for the most part, are within the hot section. Specific parameters of concern are dynamic gas temperature, heat flux, airfoil surface temperature, and strain on airfoils and combustor liners. In order to minimize the intrusiveness of surface-mounted sensors, a considerable effort was expended to develop thin-film sensors for surface temperature, strain, and heat flux measurements. Most of the work described is sufficiently advanced that sensors were used and useful data were obtained. The notable exception is the work to develop a high-temperature static strain measuring capability; this work is still in progress.

Englund, David R.

1987-01-01

437

Magnetic Sensor Based on Side-Polished Fiber Bragg Grating Coated With Iron Film  

Microsoft Academic Search

This paper presents a novel fiber-optic magnetic sensor based on a side-polished fiber Bragg grating coated with thin iron film. The Bragg wavelength shift of 0.08 nm was measured at the distance of 0.38 mm between fiber sensor and Nd-Fe-B magnet with remanent flux density of 1.115 T. We demonstrate the ability to measure magnetic fields using such a device

Chuen-Lin Tien; Chang-Chou Hwang; Hong-Wei Chen; Wen Fung Liu; Shane-Wen Lin

2006-01-01

438

Synthesis and Characterization of Carbon Nitride Films for Micro Humidity Sensors  

PubMed Central

Nano-structured carbon nitride (CNx) films were synthesized by a reactive RF magnetron sputtering system with a DC bias under various deposition conditions, and their physical and electrical properties were investigated with a view to using them for micro humidity sensors. The FTIR spectra of the deposited films showed a C=N stretching band in the range of 1600?1700 cm-1, depending on the amount of nitrogen incorporation. The carbon nitride films deposited on the Si substrate had a nano-structured surface morphology with a grain size of about 20 nm, and their deposition rate was 1.5 ?m/hr. The synthesized films had a high electrical resistivity in the range of 108 to 109 ?cm, depending on the deposition conditions. The micro humidity sensors showed a good linearity and low hysteresis between 5 ? 95 %RH.

Lee, Sung Pil

2008-01-01

439

Modified ZSM-5 zeolite film-integrated fiber optic sensors for ammonia detection  

NASA Astrophysics Data System (ADS)

This paper reports the development of surface modified ZSM-5 zeolite thin-film coated long-period fiber grating (LPFG) sensors for in situ detection of ammonia (NH3). The sensor was fabricated by growing MFI-type zeolite thin film (i.e. ZSM-5 with Si/Al ratio of 15) on the optical fiber grating by in situ hydrothermal crystallization. The sensor measures ammonia concentration by monitoring the molecular adsorption-induced shift of LPFG resonant wavelength (?R) in near infrared (IR) region. Upon loading the analyte (NH3) molecules, the refractive index of the zeolite film changes in the close vicinity of the fiber index where the LPFG has a large response to achieve high sensitivity. High sensitivity of this sensor also comes from the ability of the nanoporous zeolite to effectively concentrate the target molecules by selective adsorption. The sensor was capable of sensitive detection of ammonia at lower ppm level. The zeolite's internal surface was modified by ion exchange with NH4+ followed by thermal treatments to enhance the surface acidity. The acidic ZSM-5 (i.e. H-ZSM-5) film exhibited higher sensitivity and improved selectivity for NH3.

Tang, Xiling; Tang, Zhong; Kim, Seok-Jhin; Dong, Junhang

2009-05-01

440

MEMS-Based Thin Film and Resonant Chemical Sensors  

Microsoft Academic Search

To satisfy demands for detecting chemicals in the environment and for real time monitoring of chemical processes, ever more sophisticated sensors, often able to operate under harsh conditions, are required to detect a rapidly growing range of chemical species. In this paper, we focus on progress being made to miniaturize and improve the performance of sensors by the integration of

H. L. Tuller

441

Novel strategies for development of gas sensors for combustion and medical applications  

NASA Astrophysics Data System (ADS)

Chemical gas sensors can have an enormous impact on optimizing complex processes as well as facilitate disease diagnosis. In this article, we demonstrate how sensing of gas molecules is influencing the next generation of engines for transportation applications, as well as in disease diagnosis. In such applications, the demands on sensors are quite extreme. Not only does the device have to detect the gas of interest with high sensitivity, it also has to discriminate against other species present in a complex environment, such as combustion exhaust and human breath. In addition, the sensors will need to have as small a footprint as possible in size and power requirements. With these varied requirements in mind, only electrochemical sensors have the potential to be practical. This article focuses on nitric oxide (NOx) and ammonia (NH3) sensor necessary for emission control of next generation, high efficiency, lean burn engines and nitric oxide (NO) sensor for breath analysis for diagnosis of respiratory diseases. In all of these applications, there has been significant recent commercial activity. We indicate the electrochemical principles of these commercial sensors, and the development from our research group. We present potentiometric total NOx sensors that can operate in harsh environments, and impedance-based NH3 sensor for transportation industry. For detecting NO in human breath, we have demonstrated two strategies, the first using a resistive approach, and the second with an array of potentiometric sensors. Data from these sensors, their limitations as well as novel MEMS-based approaches for miniaturization is presented.

Fulmer, Adam; Mullen, Max; Sun, Chenhu; Dutta, Prabir K.

2014-06-01

442

Modeling analysis and experimental study on the optical fiber hydrogen sensor based on Pd-Y alloy thin film.  

PubMed

The failure of hydrogen sensor with palladium film is primarily the phase transition of PdH. To restrain this, a novel palladium and yttrium (Pd-Y) alloy film was prepared by the co-sputtering method and was used to design an optical fiber hydrogen sensor. A sensor model was established based on the optical film matrix method. The relationship between the reflectivity of the film and the hydrogen concentration was discussed. The experimental results show that this sensor is superior to the traditional sensor with Pd in shortening the response and recovery time, restraining drift, and promoting repeatability. The Pd-Y alloy film is an extremely promising material for detecting hydrogen. PMID:22852716

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

2012-07-01

443

Nano-clay\\/poly(vinylidene fluoride) composite films as sensor and actuator element  

Microsoft Academic Search

Poly(vinylidene fluoride) (PVDF) is a piezoelectric polymer material. In general, it is necessary to give large stretch to PVDF film when PVDF film is used as sensor or actuator element. However, we recently found that PVDF shows piezoelectricity without large stretch if nano-clays are uniformly dispersed into it. The aim of present study is to investigate the possibilities of nano-clay\\/PVDF

Go Murasawa; Daisuke Wakabayashi; Eiji Yamada; Akihiro Nishioka; Ken Miyata; Tomonori Koda

2010-01-01

444

Stretchable and flexible high-strain sensors made using carbon nanotubes and graphite films on natural rubber.  

PubMed

Conventional metallic strain sensors are flexible, but they can sustain maximum strains of only ~5%, so there is a need for sensors that can bear high strains for multifunctional applications. In this study, we report stretchable and flexible high-strain sensors that consist of entangled and randomly distributed multiwall carbon nanotubes or graphite flakes on a natural rubber substrate. Carbon nanotubes/graphite flakes were sandwiched in natural rubber to produce these high-strain sensors. Using field emission scanning electron microscopy, the morphology of the films for both the carbon nanotube and graphite sensors were assessed under different strain conditions (0% and 400% strain). As the strain was increased, the films fractured, resulting in an increase in the electrical resistance of the sensor; this change was reversible. Strains of up to 246% (graphite sensor) and 620% (carbon nanotube sensor) were measured; these values are respectively ~50 and ~120 times greater than those of conventional metallic strain sensors. PMID:24399158

Tadakaluru, Sreenivasulu; Thongsuwan, Wiradej; Singjai, Pisith

2014-01-01

445

Development of Micro-Heaters with Optimized Temperature Compensation Design for Gas Sensors  

PubMed Central

One of the key components of a chemical gas sensor is a MEMS micro-heater. Micro-heaters are used in both semiconductor gas sensors and NDIR gas sensors; however they each require different heat dissipation characteristics. For the semiconductor gas sensors, a uniform temperature is required over a wide area of the heater. On the other hand, for the NDIR gas sensor, the micro-heater needs high levels of infrared radiation in order to increase sensitivity. In this study, a novel design of a poly-Si micro-heater is proposed to improve the uniformity of heat dissipation on the heating plate. Temperature uniformity of the micro-heater is achieved by compensating for the variation in power consumption around the perimeter of the heater. With the power compensated design, the uniform heating area is increased by 2.5 times and the average temperature goes up by 40 C. Therefore, this power compensated micro-heater design is suitable for a semiconductor gas sensor. Meanwhile, the poly-Si micro-heater without compensation shows a higher level of infrared radiation under equal power consumption conditions. This indicates that the micro-heater without compensation is more suitable for a NDIR gas sensor. Furthermore, the micro-heater shows a short response time of less than 20ms, indicating a very high efficiency of pulse driving. PMID:22163756

Hwang, Woo-Jin; Shin, Kyu-Sik; Roh, Ji-Hyoung; Lee, Dae-Sung; Choa, Sung-Hoon

2011-01-01

446

Preparation of a stable sol suspension of Pd-loaded SnO? nanocrystals by a photochemical deposition method for highly sensitive semiconductor gas sensors.  

PubMed

A stable sol suspension of Pd-loaded SnO(2) nanocrystals, which is valid for both fundamental studies of semiconductor gas sensor and fabrications of a micro gas sensor, was fabricated by the photochemical deposition of PdCl(4)(2-) onto SnO(2) in an aqueous solution. UV light was irradiated on a mixture of a SnO(2) sol obtained through a hydrothermal treatment of stannic acid gel in the presence of PdCl(4)(2-) and ethanol/water at pH 2. A stable sol suspension of Pd-loaded SnO(2) was successfully obtained by controlling the pH of the above suspension to 10.5 after UV irradiation. Thin-film type sensor devices (film thickness ?200 nm) using Pd-loaded SnO(2) nanocrystal were successfully fabricated by a spin-coating method. Gas sensing measurements showed that the deposition of Pd on the SnO(2) nanocrystals resulted in large electrical sensitization effect. The maximum gas sensitization effect was obtained at 0.125 mol % Pd loading. Moreover, the Pd loading lowered the temperature, in which the maximum sensor response to H(2) was obtained, due to the efficient catalytic combustion of H(2) on Pd. PMID:22869519

Yuasa, Masayoshi; Kida, Tetsuya; Shimanoe, Kengo

2012-08-01

447

An electromagnetic cavity sensor for multiphase measurement in the oil and gas industry  

NASA Astrophysics Data System (ADS)

The oil and gas industry require accurate sensors to monitor fluid flow in pipelines in order to manage wells efficiently. The sensor described in this paper uses the different relative permittivity values for the three phases: oil, gas and water to help determine the fraction of each phase in the pipeline, by monitoring the resonant frequencies that occur within an electromagnetic cavity. The sensor has been designed to be non-intrusive. This is advantageous, as it will prevent the sensor being damaged by the flow through the pipeline and allow pigging, the technique used for cleaning rust and wax from the inside of the pipeline using blades or brushes.

Al-Hajeri, S.; Wylie, S. R.; Stuart, R. A.; Al-Shamma'a, A. I.

2007-07-01

448

Hydrogen sensing characteristics of an electrodeposited WO 3 thin film gasochromic sensor activated by Pt catalyst  

Microsoft Academic Search

The hydrogen gas sensing performance of platinum (Pt) catalyst activated tungsten trioxide (WO3) thin films were investigated in the present study. The WO3 thin films exhibited a gasochromic effect; i.e., a reversible change in color from transparent when in air to blue when in hydrogen (H2). All processes proceeded rapidly at room temperature. The films were prepared by the electrodeposition

Wen-Chia Hsu; Chih-Chieh Chan; Chia-Hsiang Peng; Chung-Chieh Chang

2007-01-01

449

Integration of thin film giant magnetoimpedance sensor and surface acoustic wave transponder  

NASA Astrophysics Data System (ADS)

Passive and remote sensing technology has many potential applications in implantable devices, automation, or structural monitoring. In this paper, a tri-layer thin film giant magnetoimpedance (GMI) sensor with the maximum sensitivity of 16%/Oe and GMI ratio of 44% was combined with a two-port surface acoustic wave (SAW) transponder on a common substrate using standard microfabrication technology resulting in a fully integrated sensor for passive and remote operation. The implementation of the two devices has been optimized by on-chip matching circuits. The measurement results clearly show a magnetic field response at the input port of the SAW transponder that reflects the impedance change of the GMI sensor.

Li, Bodong; Salem, Nedime Pelin M. H.; Giouroudi, Ioanna; Kosel, Jrgen

2012-04-01

450

A novel ethanol gas sensor-ZnS/ cyclohexylamine hybrid nanowires.  

PubMed

We fabricated a novel ethanol gas sensor based on organic-inorganic ZnS/cyclohexylamine (CHA) nanowires via a solvothermal route. The sensor exhibited significantly better performance with response time of approximately 0.6 s and recovery time of approximately 10 s even under a low ethanol concentration and the high surface area, small nanofiber diameter, and hybrid nature made the ZnS/CHA nanowire gas sensor have high sensitivity to ethanol gas at a lower operating current of 160 mA. Moreover, the gas sensing mechanism was proposed on the basis of the two simultaneous steps to explain the adsorbing process due to the hybrid nature. This work indicates that the ZnS/CHA hybrid can be a novel candidate for the ethanol gas sensor with high performance. PMID:21449358

Xu, Lin; Song, Hongwei; Zhang, Tong; Fan, Huitao; Fan, Libo; Wang, Yu; Dong, Biao; Bai, Xue

2011-03-01

451

Gas and aerosol wall losses in Teflon film smog chambers  

SciTech Connect

Large smog chambers (approx.60 m/sup 3/) constructed of FEP Teflon film are frequently used to study photochemistry and aerosol formation in model chemical systems. In a previous paper a theory for aerosol wall loss rates in Teflon film smog chambers was developed; predicted particle loss rates were in good agreement with measured rates. In the present paper, measurements of wall deposition rates and the effects of wall losses on measurements of gas-to-particle conversion in smog chambers are discussed. Calculations indicate that a large fraction of the aerosol formed in several smog chamber experiments was on the chamber walls at the end of the experiment. Estimated values for particulate organic carbon yield for several precursor hydrocarbons increased by factors of 1.3-6.0 when wall deposition was taken into account. The theory is also extended to loss rates of gaseous species. Such loss rates are either limited by diffusion through a concentration boundary layer near the surface or by uptake at the surface. It is shown that for a typical 60-m/sup 3/ Teflon film smog chamber, gas loss rates are limited by surface reaction rates if mass accommodation coefficients are less than 6 x 10/sup -6/. It follows that previously reported loss rates of several gases in a chamber of this type were limited by surface reactions.

McMurry, P.H.; Grosjean, D.

1985-12-01

452

Membrane-Based Characterization of a Gas Component A Transient Sensor Theory  

PubMed Central

Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper presents a transient theory of a planar, membrane-based sensor cell for measuring gas from both initial conditions: dynamic and thermodynamic equilibrium. Using this theory, the ranges for which previously developed, simpler approaches are valid will be discussed; these approaches are of vital interest for membrane-based gas sensor applications. Finally, a new theoretical approach is introduced to identify varying gas components by arranging sensor cell pairs resulting in a concentration independent gas-specific critical time. Literature data for the N2, O2, Ar, CH4, CO2, H2 and C4H10 diffusion coefficients and solubilities for a polydimethylsiloxane membrane were used to simulate gas specific sensor responses. The results demonstrate the influence of (i) the operational mode; (ii) sensor geometry and (iii) gas matrices (air, Ar) on that critical time. Based on the developed theory the case-specific suitable membrane materials can be determined and both operation and design options for these sensors can be optimized for individual applications. The results of mixing experiments for different gases (O2, CO2) in a gas matrix of air confirmed the theoretical predictions. PMID:24608004

Lazik, Detlef

2014-01-01

453

A stretchable strain sensor based on a metal nanoparticle thin film for human motion detection.  

PubMed

Wearable strain sensors for human motion detection are being highlighted in various fields such as medical, entertainment and sports industry. In this paper, we propose a new type of stretc