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1

WO 3 thick-film gas sensors  

Microsoft Academic Search

Tungsten trioxide is a promising material for NOx gas sensors. This paper describes the preparation of tungsten trioxide thick films by the use of the traditional screen-printing technology. We present the characterization of both their structural properties by means of XRD measurements and the film morphology by the SEM microscope studies, and the electrical response of the films of various

A. A. Tomchenko; V. V. Khatko; I. L. Emelianov

1998-01-01

2

Nano-Hydroxyapatite Thick Film Gas Sensors  

SciTech Connect

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

Khairnar, Rajendra S.; Mene, Ravindra U.; Munde, Shivaji G.; Mahabole, Megha P. [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606 (India)

2011-12-10

3

Gas sensors based on nanoparticle WO3 thick films  

Microsoft Academic Search

The gas sensing properties of chemical sensors based on nanoparticle WO3 thick films, doped with indium and bismuth, are studied. Commercial WO3 nanopowder with spherical diameter up to 33.1 nm was mixed with either InCl3 or BiCl3. The sensing films of the sensors were prepared using three different concentrations of each doping metal (1.5 wt.%, 3.0 wt.% and 5.0 wt.%,

V. Khatko; R. Ionescu; E. Llobet; X. Vilanova; J. Brezmes; J. Hubalek; K. Malysz; X. Correig

2004-01-01

4

Electron Beam Evaporation of Tungsten Oxide Films for Gas Sensors  

Microsoft Academic Search

Pure and iron incorporated nanostructured Tungsten Oxide (WO3) thin films were investigated for gas sensing applications using noise spectroscopy. The WO3 sensor was able to detect lower concentrations (1-10 ppm) of NH3, CO, CH4, and Acetaldehyde gases at operating temperatures between 100°C to 250°C. The iron-doped Tungsten Oxide sensor ( WO3:Fe) showed some response to Acetaldehyde gas at relatively higher

T. Tesfamichael

2010-01-01

5

Sensing characteristics of tin oxide thick film gas sensor  

Microsoft Academic Search

Thick film gas sensor of tin oxide based materials has been developed by screen printing method, and its sensing characteristics have been examined for some gases. To perform the method, tin oxide fine power with the size about 0.5 ?m in diameter was prepared through the fine crystallization in liquid phase, and was mixed with glass frits as a binder

Takashi Oyabu; Tetsuo Osawa; Toshiji Kurobe

1982-01-01

6

Development of VOC analyzer using a WO3 thick film based gas sensor  

Microsoft Academic Search

This paper describes a VOC gas analyzer system developed using an original gas sensor and gas chromatography for the detection of aromatic hydrocarbon gases. The sensor is based on a WO3 thick film where Pd and Pt are applied as catalyst to a limited area of the film to promote sensitivity and improve gas selectivity. The sensor shows extremely high

K. Kanda; T. Kuse

2004-01-01

7

Improved zinc oxide film for gas sensor applications  

Microsoft Academic Search

Zinc oxide (ZnO) is a versatile material for different commercial applications such as transparent electrodes, piezoelectric\\u000a devices, varistors, SAW devices etc because of its high piezoelectric coupling, greater stability of its hexagonal phase and\\u000a its pyroelectric property. In fact, ZnO is a potential material for gas sensor applications. Good quality ZnO films were deposited\\u000a on glass and quartz substrates by

S. Roy; S. Basu

2002-01-01

8

NiO thin-film formaldehyde gas sensor  

Microsoft Academic Search

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

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

2001-01-01

9

Fabrication of carbon tetrachloride gas sensors using indium tin oxide thin films  

Microsoft Academic Search

Indium tin oxide (ITO) polycrystalline thin films grown on alumina substrates by the thermal evaporation technique are used for fabricating gas sensors to detect carbon tetrachloride (CCl4). The electrical conductance of the sensors appears to increase and decrease on exposure to gaseous CCl4, depending on the operating temperature. The thin-film gas sensors with a thickness of about 100 nm shows

N. G. Patel; K. K. Makhija; C. J. Panchal; D. B. Dave; V. S. Vaishnav

1995-01-01

10

Thermal-Power Consumption and Heat Transfer Coefficients in Micro-thin-film Gas Sensors  

Microsoft Academic Search

The thermal-power consumption is a important parameter of gas sensor. The temperature distribution of thin film gas sensor, temperature of metal guard, the dissipating heat of lead-wires and the regularity of sensors heat transfer coefficient varying with size of heat-transfer surface and working temperature was studied. The formula of thermal-power consumption of micro-thin-film gas sensors yielded in this paper, from

Liu Xiaojian; Qu Lu; Li Donghua; Xing Jianping; Qiu Nanwan

2006-01-01

11

Mn doped nanostucture ZnO thin film for photo sensor and gas sensor application  

NASA Astrophysics Data System (ADS)

Mn doped nanostructure ZnO thin film prepared by soft chemically route method. ZnO thin films were deposited on glass substrate by successive ionic layer adsorption and reaction technique (SILAR). After deposit ZnO thin film dipped in MnSO4 solution for 1 min. The optical properties as absorbance were determined using UV-Spectrophotometer and band gap was also calculated. The Structural properties were studied by XRD. The improvement in gas sensing properties was found to enhance after doping of Mn on ZnO thin film. The Photo Sensor nature was calculated by I-V characteristics.

Mahajan, Sandip V.; Upadhye, Deepak S.; Shaikh, Shahid U.; Birajadar, Ravikiran B.; Siddiqui, Farha Y.; Ghule, Anil V.; Sharma, Ramphal

2013-02-01

12

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

13

Single-Walled Carbon Nanotube Thin-Film Sensor for Ultrasensitive Gas Detection  

NASA Astrophysics Data System (ADS)

We demonstrated a gas sensor fabricated by growing a single-walled carbon nanotube (SWNT) thin film directly on a conventional sensor substrate. NO2 and Cl2 were detected down to the ppb level under room-temperature operation with a fast response. Using an electrical breakdown technique, gas response sensitivity was improved by an order of magnitude. The relationship between gas concentration and sensor response was derived based on the Langmuir adsorption isotherm, predicting a detection limit of 8 ppb for NO2. The SWNT thin-film gas sensor exhibits merits over other types of sensors by virtue of its simplicity in fabrication and feasible application.

Wongwiriyapan, Winadda; Honda, Shin-ichi; Konishi, Hirofumi; Mizuta, Tomoaki; Ikuno, Takashi; Ito, Tatsuya; Maekawa, Toru; Suzuki, Kengo; Ishikawa, Hiroshi; Oura, Kenjiro; Katayama, Mitsuhiro

2005-04-01

14

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

SciTech Connect

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

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

1996-11-01

15

Diamond Film Gas Sensors for Leak Detection of Semiconductor Doping Gases  

NASA Astrophysics Data System (ADS)

Gas sensors for leak detection of toxic semiconductor doping gases such as PH3, B2H6, and AsH3 were fabricated using diamond films. The sensors have a double-layered structure composed of undoped and B-doped polycrystalline diamond layers with Pt electrodes. The relative changes in the resistance of the sensors were typically 10-20% for 0.2 ppm PH3 in air, and the highest value was over 100%. It was concluded that the diamond film gas sensors fabricated in the present work would be practically applicable as compact solid-state sensors with an advantage over the conventional aqueous electrolyte sensors.

Hayashi, Kazushi; Yokota, Yoshihiro; Tachibana, Takeshi; Miyata, Koichi; Kobashi, Koji; Fukunaga, Tetsuya; Takada, Tadashi

2000-01-01

16

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

NASA Astrophysics Data System (ADS)

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

Imai, Yuji; Kimura, Yasuo; Niwano, Michio

2012-10-01

17

MICRO-MACHINED THIN FILM HYDROGEN GAS SENSORS  

Microsoft Academic Search

The ability to detect gaseous hydrogen is of critical importance to acceptance and utilization of hydrogen as an energy carrier. Micro-machined gas sensors are a new generation of sensor technology combining existing integrated circuit fabrication technology with novel deposition and etching processing. This results in a new device structure, known as a \\

Frank DiMeo; Ing-Shin Chen; Philip Chen; Jeffrey Neuner Michele Stawasz; James Welch; A. Rohrl

18

Nano-structured thin-film Pt catalyst for thermoelectric hydrogen gas sensor  

Microsoft Academic Search

A hydrogen gas sensor using thermoelectric thin-film of nickel oxide with platinum catalyst thin-film on half of its surface Pt\\/NiO\\/alumina was fabricated and showed prominent selectivity for hydrogen gas. The platinum catalyst thin-film plays the most important role for its detection mechanism and its catalytic activity which depends both on surface morphology and thickness was investigated using Pt\\/Si. The surface

Masahiko Matsumiya; Woosuck Shin; Noriya Izu; Norimitsu Murayama

2003-01-01

19

Nano-WO3 film modified macro-porous silicon (MPS) gas sensor  

NASA Astrophysics Data System (ADS)

We prepared macro-porous silicon (MPS) by electrochemical corrosion in a double-tank cell on the surface of single-crystalline P-type silicon. Then, nano-WO3 films were deposited on MPS layers by DC facing target reactive magnetron sputtering. The morphologies of the MPS and WO3/MPS samples were investigated by using a field emission scanning electron microscope. The crystallization of WO3 and the valence of the W in the WO3/MPS sample were characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The gas sensing properties of MPS and WO3/MPS gas sensors were thoroughly measured at room temperature. It can be concluded that: the WO3/MPS gas sensor shows the gas sensing properties of a P-type semiconductor gas sensor. The WO3/MPS gas sensor exhibits good recovery characteristics and repeatability to 1 ppm NO2. The addition of WO3 can enhance the sensitivity of MPS to NO2. The long-term stability of a WO3/MPS gas sensor is better than that of an MPS gas sensor. The sensitivity of the WO3/MPS gas sensor to NO2 is higher than that to NH3 and C2H5OH. The selectivity of the MPS to NO2 is modified by deposited nano-WO3 film.

Peng, Sun; Ming, Hu; Mingda, Li; Shuangyun, Ma

2012-05-01

20

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

Microsoft Academic Search

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

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

1999-01-01

21

Laser patterning of thin-film electrochemical gas sensors  

NASA Astrophysics Data System (ADS)

We have patterned a CO 2 thin film electrochemical sensor using Xe laser ablation of Pt, Nasicon and Na 2CO 3 thin films. A thin metallic absorbing layer on Nasicon is used to achieve reproducible ablation of the ionic conductor with no piercing of the buried Pt electrode. Processing conditions are 10 J/cm 2 pulses with a scanning velocity of 500 ?m/s for Pt and 6.3 J/cm 2 pulses with a scanning velocity of 100 ?m/s for Nasicon. Nasicon is ablated in the form of flakes suggesting an ablation in the solid phase. Fabrication of an integrated heating element and a micro-thermometer by laser ablation is also presented.

Lecours, A.; Caron, M.; Ciureanu, P.; Turcotte, G.; Ivanov, D.; Yelon, A.; Currie, J. F.

1996-04-01

22

Semiconductor gas sensor based on Pd-doped SnO 2 nanorod thin films  

Microsoft Academic Search

SnO2 nanorod thin films have been prepared by plasma-enhanced chemical vapor deposition (PECVD) with postplasma treatment. The SnO2 nanorod thin films were surface modified with Pd nanoparticles and their sensing properties towards H2 and ethanol gas were studied. It was found that the Pd-doped SnO2 nanorod thin film sensor exhibits 6 and 2.5 times better response to 1000ppm H2 and

Y. C. Lee; Hui Huang; O. K. Tan; M. S. Tse

2008-01-01

23

Room temperature pulsed laser deposited ZnO thin films as photoluminiscence gas sensors  

NASA Astrophysics Data System (ADS)

Zinc oxide thin films with optical sensing capabilities for NO2 have been elaborated by pulsed laser deposition (PLD) onto glass substrates at room temperature with Nd:YAG laser (1064 nm). Morphology, chemical composition and optical characteristics of the films were evaluated as a function of laser fluence, gas pressure and target-to-substrate distance. Films exhibit excellent morphological and optical (transmittance and photoluminescence) properties. The films have been evaluated as fluorescence sensors for NO2 in the concentration range between 26 and 200 ppm.

Padilla-Rueda, D.; Vadillo, J. M.; Laserna, J. J.

2012-10-01

24

Selective NH 3 gas sensor based on Langmuir-Blodgett polypyrrole film  

Microsoft Academic Search

Polypyrrole thin films have been deposited onto a glass substrate by the Langmuir-Blodgett technique to fabricate a selective ammonia (NH3) gas sensor. The d.c. electrical resistance of the sensing elements is found to exhibit a specific increase upon exposure to different gases such as NH3, CO, CH4, H2 in N2 and pure O2. The polypyrrole thin-film detector shows a considerable

M. Penza; E. Milella; M. B. Alba; A. Quirini; L. Vasanelli

1997-01-01

25

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

NASA Astrophysics Data System (ADS)

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

Prasad, Arun Kapaleeswaran

26

Molecular Interactions Between Alcohols and Metal Phthalocyanine Thin Films for Optical Gas Sensor Applications  

Microsoft Academic Search

Optically active organic gas sensors represent a promising molecular sensing device with low power consumption. We report\\u000a experimental and computational investigations into the molecular interactions of metal phthalocyanine thin films with alcohol\\u000a vapor. In the gas-sensing regime, the interactions of zinc phthalocyanine and alcohol molecules were studied by the Density\\u000a Functional Theory (DFT) calculations, in comparison to the x-ray absorption

Sureeporn Uttiya; Sumana Kladsomboon; Onanong Chamlek; Wiriya Suwannet; Tanakorn Osotchan; Teerakiat Kerdcharoen; Martin Brinkmann; Sirapat Pratontep

2009-01-01

27

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

28

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

Microsoft Academic Search

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

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

2002-01-01

29

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

NASA Astrophysics Data System (ADS)

Porous tungsten oxide films were deposited onto a sensor substrate with a Si bulk-micromachined hotplate, by drop-coating isopropyl alcohol solution of highly crystalline tungsten oxide (WO2.72) nanorods with average 75 nm length and 4 nm diameter. The temperature-dependent gas sensing characteristics of the films have been investigated over the mild temperature range from 20 to 250 °C. While the sensing responses for ammonia vapor showed increase in electrical conductivity at temperatures above 150 °C as expected for n-type metal oxide sensors, they exhibited the opposite behavior of unusual conductivity decrease below 100 °C. Superb sensing ability of the sensors at room temperature in conjunction with their anomalous conductivity behavior might be attributed to unique nanostructural features of very thin, nonstoichiometric WO2.72.

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

2005-05-01

30

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

Microsoft Academic Search

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

G. S. Trivikrama Rao; D Tarakarama Rao

1999-01-01

31

Thin-film-bulk-acoustic-resonator gas sensor for the detection of organophosphate vapor detection  

Microsoft Academic Search

A novel design of an organophosphate vapor sensor based on a thin film bulk acoustic resonator (TFBAR) is presented. The TFBAR device is consisted of an AlN piezoelectric stack and a Mo\\/AlN Bragg reflector. Poly (vinylidene fluoride) (PVDF) is coated on the surface of the piezoelectric stack as the special sensitive layer. The concentration of the target gas can be

Jing-jing Wang; Da Chen; Lu-yin Zhang; Yan Xu

2011-01-01

32

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

SciTech Connect

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

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

2009-01-08

33

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

34

Mono, multi-layer nanostructured porous films and gas sensors  

Microsoft Academic Search

A simple and flexible strategy is presented for synthesis of mono or multi-layer nanostructured ordered porous films on any desired substrates with flat or even curved surface, based on the fact that polystyrene sphere colloidal monolayer on glass substrate can lift off and floated on some precursor solutions, which can, in turn, be transferred onto any substrates by picking it

Fengqiang Sun; Weiping Cai; Yue Li; Lichao Jia; Fang Lu

2005-01-01

35

A novel tin oxide-based recoverable thick film SO 2 gas sensor promoted with magnesium and vanadium oxides  

Microsoft Academic Search

An SnO2-based thick film gas sensor was developed to detect sulfur dioxide (SO2) gas at the ppm level. The SnO2-based sensors were prepared by mixing tin oxide with various promoters such as V2O5, MoO3, Sb2O3, Al2O3, CeO2, and MgO. Their sensor responses and recovery behaviors were investigated in a flow system. It was found that the SnO2-based gas sensor promoted

Soo Chool Lee; Byung Wook Hwang; Soo Jae Lee; Ho Yun Choi; Seong Yeol Kim; Suk Yong Jung; Dhanusuraman Ragupathy; Duk Dong Lee; Jae Chang Kim

36

A novel quartz crystal microbalance gas sensor based on porous film coatings. A high sensitivity porous poly(methylmethacrylate) water vapor sensor.  

PubMed

We describe a novel and generally applicable approach for creating voids in films deposited on the surface of solid substrates. Such films are advantageous when a quartz crystal microbalance (QCM) is the basis of a sensor. We show that films with large void volumes produce more sensitive sensors than with the original film. Poly(methylmethacrylate) (PMMA) was used as the polymer layer deposited on a quartz crystal microbalance (QCM) to demonstrate our technique for the model system of water vapor analysis in flowing nitrogen gas. A film of pure PMMA on a QCM is a sensor for water vapor in a gas phase. A more sensitive sensor was created by dip coating QCM crystals into solutions containing mixtures of PMMA and poly(D,L-lactide) (PDLL) and then evaporating the solution films on the QCM crystals to form mixed polymer films of varying PDLL content. The PDLL was then removed from the mixed polymer films by exposure to a NaOH solution to form pure PMMA films having various void volumes. A leached PMMA film that originally contained 50% by weight PDLL had a 3.7 times larger QCM sensitivity for water vapor than a pure PMMA film. PMID:23764449

Yoo, Ho Yeon; Bruckenstein, Stanley

2013-05-06

37

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

Microsoft Academic Search

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

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

2003-01-01

38

Detection of liquid petroleum gas using mixed nanosized tungsten oxide-based thick-film semiconductor sensor  

Microsoft Academic Search

The thick-film semiconductor sensor for liquid petroleum gas (LPG) detection was fabricated using a mixed WO3-based sensor. We present the characterization of both their structural properties by means of XRD measurements and the electrical characteristics by using gas-sensing properties. The sensing characteristics such as sensitivity, working range, cross-sensitivity and response time were studied by using nanosized WO3-based mixed with different

G. N. Chaudhari; A. M. Bende; A. B. Bodade; S. S. Patil; S. V. Manorama

2006-01-01

39

Thin film hydrogen sensor  

DOEpatents

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

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

1994-01-01

40

Molecular Interactions Between Alcohols and Metal Phthalocyanine Thin Films for Optical Gas Sensor Applications  

NASA Astrophysics Data System (ADS)

Optically active organic gas sensors represent a promising molecular sensing device with low power consumption. We report experimental and computational investigations into the molecular interactions of metal phthalocyanine thin films with alcohol vapor. In the gas-sensing regime, the interactions of zinc phthalocyanine and alcohol molecules were studied by the Density Functional Theory (DFT) calculations, in comparison to the x-ray absorption spectroscopy. The DFT results reveal a reversible charge interaction mechanism between the zinc atom and the oxygen atom in the alcohol OH group, which corresponds to a shift in the x-ray absorption edge of the zinc atom. In the irreversible interaction regime, the effect of saturated alcohol vapor on spin-coated zinc phthalocyanine films was studied by the phase contrast microscopy, the optical absorption spectroscopy, and the transmission electron microscopy. Annealing the spin-coated films in saturated methanol vapor was found to induce an irreversible structural transformation from an amorphous to a crystalline phase, similar to the effect of a thermal annealing process. These crystallization processes of the zinc phthalocyanine films were also found to enhance their stability and alcohol sensing performance.

Uttiya, Sureeporn; Kladsomboon, Sumana; Chamlek, Onanong; Suwannet, Wiriya; Osotchan, Tanakorn; Kerdcharoen, Teerakiat; Brinkmann, Martin; Pratontep, Sirapat

41

Fiber optic hydrogen sulfide gas sensor utilizing surface plasmon resonance of Cu/ZnO thin films  

NASA Astrophysics Data System (ADS)

We report a surface plasmon resonance based fiber optic hydrogen sulphide gas sensor using Cu/ZnO thin films. The sensor works on wavelength modulation scheme. The fiber optic probe was fabricated by removing the cladding of appropriate length from the fiber and depositing copper and ZnO thin films on the unclad core by thermal evaporation technique. The presence of hydrogen sulphide gas around the probe changes the dielectric function of zinc oxide and a dip is observed in transmitted spectrum. With the increase in the gas concentration shift in the resonance wavelength has been observed. The proposed sensor can be used for online monitoring and remote sensing of hydrogen sulphide gas in the environment.

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

2013-05-01

42

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. Bârsan; U. Weimar; A. Hierlemann

2006-01-01

43

Development of a miniaturized NO2 gas sensor based on nanoparticles WO3 thin film on interdigitated electrodes  

Microsoft Academic Search

A miniaturized semiconducting metal oxide NO2 gas sensor with integrated micro heater is reported in this paper. The sensor has the size of 1×1×0.4 mm3 and detects NO2 based on the electrical conductance change of porous nanoparticles WO3 thin film, which is deposited on the interdigitated Pt electrodes. Integrated micro heater designed to provide the operating temperature above 200°C for

Dzung Viet Dao; Ling-Han Li; T. Hashishin; J. Tamaki; K. Shibuya; S. Sugiyama

2010-01-01

44

Fabrication of highly efficient fibre-optic gas sensors using SiO2\\/polymer nanoporous thin films  

Microsoft Academic Search

A highly porous nano-thin film has been deposited on the optical fibre with the aim to develop a fibre-optic gas sensor. The film was composed of alternate layers of poly(diallyldimethyl ammonium chloride) (PDDA) and silica nanoparticles of 40-50 nm in diameter deposited using the electrostatic self assembly process. As a final step of preparation, the coating was infused with the

Suguru Kodaira; Sergiy Korposh; Seung-Woo Lee; William J. Batty; Stephen W. James; R. P. Tatam

2008-01-01

45

Thick-film gas sensors based on vanadium–titanium oxide powders prepared by sol-gel synthesis  

Microsoft Academic Search

Two titania powders modified by 10 at.% of vanadium were prepared by two different sol-gel routes. The powders fired at 650 °C had the rutile structure. These powders were used to produce prototype thick-film sensors. Four series of thick-film samples were fabricated by screen-printing, fired for 1 h at 650 and 850 °C. The morphology and gas-sensing properties were examined and compared

Maria Cristina Carotta; Matteo Ferronia; Sandro Gherardi; Vincenzo Guidi; Cesare Malagù; Giuliano Martinelli; Michele Sacerdoti; Maria Luisa Di Vona; Silvia Licoccia; Enrico Traversa

2004-01-01

46

Impedance spectroscopy analysis of TiO 2 thin film gas sensors obtained from water-based anatase colloids  

Microsoft Academic Search

In this work impedance spectroscopy technique was employed in order to characterize the gas-sensing behavior of undoped titanium dioxide (TiO2) polycrystalline thin films. The electrical measurements were performed in a sensor-testing chamber that allows independent control of temperature, pressure, gas composition and flow rate. Frequency measurements, in the range from 40Hz to 110MHz, were performed in order to evaluate the

M. A. Ponce; R. Parra; R. Savu; E. Joanni; P. R. Bueno; M. Cilense; J. A. Varela; M. S. Castro

2009-01-01

47

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

Microsoft Academic Search

Chemical sensors that monitor gas concentrations through changes in the electrical resistance of their sensing elements are called resistive type detectors. Gas specificity is a highly desirable property in gas sensing, and is defined as the preferred response to a particular gas in the presence of other interfering compounds. The lack of specificity and limited selectivity of existing chemosensors often

Arun Kapaleeswaran Prasad

2005-01-01

48

Thin film hydrogen sensor  

DOEpatents

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

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

1994-11-22

49

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

50

Carbon dioxide sensitivity of La-doped thick film tin oxide gas sensor  

Microsoft Academic Search

The CO2 sensitivity of a La-doped SnO2 thick film was characterized with variation of the La2O3 content up to 4.5mol%. Effects of mechanical milling of SnO2 powders on the CO2 sensitivity of a SnO2 thick film sensor were also studied. When exposed to 1000ppm of CO2, the sensitivity of a SnO2 thick film sensor was improved from 1.14 to 1.52

M. Y. Kim; Y. N. Choi; J. M. Bae; T. S. Oh

51

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 150°C. 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

52

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

SciTech Connect

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

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

2009-02-15

53

Pt and Pd-nanoclusters functionalized carbon nanotubes networked films for sub-ppm gas sensors  

Microsoft Academic Search

A gas chemiresistor, fabricated onto alumina using multi-walled carbon nanotubes (MWCNTs) networked films grown by radiofrequency plasma enhanced chemical vapor deposition (RF-PECVD) technology, is described for high-performance gas detection, at an operating temperature of 200°C. Functionalizations of MWCNTs tangled bundle-films with nominally 5-nm thick Pt- and Pd-nanoclusters, prepared by magnetron sputtering, provide higher sensitivity for significantly enhanced gas detection of

M. Penza; R. Rossi; M. Alvisi; G. Cassano; M. A. Signore; E. Serra; R. Giorgi

2008-01-01

54

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

Microsoft Academic Search

Nanoparticles can be generated by several different gas phase methods, such as gas deposition, laser-assisted chemical vapor deposition, and laser ablation. Some of the most important aspects - such as size-distribution, structure, and chemical composition of the generated nanoparticles (specifically W and WO3) - are presented and compared. WO3 nanoparticle films were deposited by an advanced gas deposition technique and

Peter Heszler; L. F. Reyes; Anders Hoel; Lars Landström; V. Lantto; Claes-Göran Granqvist

2003-01-01

55

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

SciTech Connect

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

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

2000-01-10

56

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

Microsoft Academic Search

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

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

1996-01-01

57

NanoWire Grown Micro Thin Film Sensors and Their Gas Sensing Properties  

Microsoft Academic Search

SnO2 nanowires were grown on the surface of SnO2 thin film by heat treatment of metal Sn film under Ar gas flow at atmospheric pressure. Generally, the nanowires of metal oxide semiconductors are known to be grown at low pressure (below 0.02 Torr) and at high temperature (over 1,000 ?). The deposited Sn metal films were annealed at temperatures of

Sang-Rok Lee; Kap-Duk Song; Yang-Rye Lim; Byung-Su Joo; Duk-Dong Lee

58

WO3 THIN FILMS DEPOSITION ON QUARTZ CRYSTAL RESONATORS FOR APPLICATIONS IN GAS SENSORS  

Microsoft Academic Search

The present research is focused on the preparation and properties of sputtered transition metal oxides thin films. WO3 films of various thickness were deposited on quartz resonators in order to use the quartz crystal microbalance method for studying their gas sensing properties. The influence of oxygen partial pressure and substrate temperature on the composition, crystal structure and optical properties of

Stefan Ivanov Boyadjiev; Milka Markova Rassovska

59

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

NASA Astrophysics Data System (ADS)

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

Takashima, Noriaki; Kimura, Mitsuteru

60

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

61

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

62

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

63

Microstructure and hydrogen gas sensitivity of amorphous (Ba,Sr)TiO 3 thin film sensors  

Microsoft Academic Search

Ferroelectric (Ba0.67Sr0.33)Ti1.02O3 thin films have been prepared by the sol–gel technology and characterized using TGA, DTA, XRD, TEM, dielectric characterizations, and gas sensing properties. The (Ba0.67Sr0.33)Ti1.02O3 thin film devices are made on Pt-coated Si substrate to detect hydrogen gas and to study gas sensing mechanism. Experimental results show that the diode I–V behavior appears in these Pd\\/amorphous (Ba,Sr)TiO3 (BST) thin

W. Zhu; O. K. Tan; Q. Yan; J. T. Oh

2000-01-01

64

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

65

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  

NASA Astrophysics Data System (ADS)

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)8) films. Gas sensor shows a response of 185% to few parts per billion level of Cl2 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

2010-12-01

66

On an indium–tin-oxide thin film based ammonia gas sensor  

Microsoft Academic Search

An ammonia sensor basing on the indium tin oxide (ITO) thin film on a quartz substrate which was fabricated by RF sputtering with substrate thermal treatment, is studied and demonstrated. From the experimental results, the good NH3 sensing performances including high response of 2312%, fast response and recovery times of 73 and 104s upon the introduction of a 1000ppm NH3\\/air

Cheng-Wei Lin; Huey-Ing Chen; Tai-You Chen; Chien-Chang Huang; Chi-Shiang Hsu; Rong-Chau Liu; Wen-Chau Liu

67

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

Microsoft Academic Search

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

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

2008-01-01

68

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

69

A micromachined thin-film gas flow sensor for microchemical reactors  

NASA Astrophysics Data System (ADS)

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

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

2006-04-01

70

Thin film hydrogen sensor  

DOEpatents

A thin film hydrogen sensor includes a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end. 5 figs.

Cheng, Y.T.; Poli, A.A.; Meltser, M.A.

1999-03-23

71

The Evolution of High Temperature Gas Sensors.  

SciTech Connect

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

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

2001-01-01

72

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

73

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

SciTech Connect

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

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

2009-06-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

75

Nanostructured SnO(2) films prepared from evaporated Sn and their application as gas sensors.  

PubMed

This paper describes the morphology, stoichiometry, microstructure and gas sensing properties of nanoclustered SnO(x) thin films prepared by Sn evaporation followed by a rheotaxial growth and thermal oxidation process. Electron microscopy was used to investigate, in detail, the evolution of the films as the oxidation temperature was increased. The results showed that the contact angle, perpendicular height, volume and microstructure of the clusters all changed significantly as a result of the thermal oxidation processes. Electron diffraction and x-ray photoelectron spectroscopy measurements revealed that after oxidation at a temperature of 600?°C, the Sn clusters were fully transformed into porous three-dimensional polycrystalline SnO(2) clusters. On the basis of these results, a prototype SnO(2) sensor was fabricated and sensing measurements were performed with H(2) and NO(2) gases. At operating temperatures of 150-200?°C the film produced measurable responses to concentrations of H(2) as low as 600 ppm and NO(2) as low as 500 ppb. PMID:21817731

Partridge, J G; Field, M R; Peng, J L; Sadek, A Z; Kalantar-Zadeh, K; Du Plessis, J; McCulloch, D G

2008-02-20

76

Microfabricated Formaldehyde Gas Sensors  

PubMed Central

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

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

2009-01-01

77

Thin-film fiber optic hydrogen and temperature sensor system  

Microsoft Academic Search

The invention discloses a sensor probe device for monitoring of hydrogen gas concentrations and temperatures by the same sensor probe. The sensor probe is constructed using thin-film deposition methods for the placement of a multitude of layers of materials sensitive to hydrogen concentrations and temperature on the end of a light transparent lens located within the sensor probe. The end

Nave

1998-01-01

78

Gas Sensors Based on Electrospun Nanofibers  

PubMed Central

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

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

2009-01-01

79

Effect of substrate on NO 2-sensing properties of WO 3 thin film gas sensors  

Microsoft Academic Search

A WO3 thin film with a 1.2 ?m thickness was deposited onto several substrates, including unpolished alumina, polished alumina, and silicon, using a thermal evaporating method with Pt meander electrodes and a heater. The WO3 thin films were annealed at 600°C in air for 2 h, thereafter, the microstructure and NO2-sensing properties of the thin films grown on the different

Dae-Sik Lee; Ki-Hong Nam; Duk-Dong Lee

2000-01-01

80

AC measurements and modeling of WO 3 thick film gas sensors  

Microsoft Academic Search

Polycrystalline WO3 films were fabricated through thick film technology. Stimulated temperature measurements showed that the intergranular Schottky barrier is not high enough to apply the depletion approximation to evaluate the fundamental parameters related to the sensing properties. Therefore, a semi-analytical approach to the Poisson's equation with the complete charge density was chosen. As a result, we could estimate the dependence

C. Malagù; M. C. Carotta; S. Gherardi; V. Guidi; B. Vendemiati; G. Martinelli

2005-01-01

81

Improved response of H2S gas sensors with CuO nanoparticles on SnO2 film  

Microsoft Academic Search

In our earlier work enhanced H2S detection characteristics were observed in a novel sensor structure consisting of uniformly distributed CuO islands on SnO2 films. Ultra-thin CuO in the form of dotted islands on SnO2 film exhibited a high sensitivity (S = 7.3 × 103) at a low operating temperature (150°C), and a fast response speed of 14 s was obtained

A. Chowdhuri; V. Gupta; R. Kumar; P. K. Patanjali; S. Mozumdar; K. Sreenivas

2003-01-01

82

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

Microsoft Academic Search

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

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

2004-01-01

83

Self-assembling of micro-patterned titanium oxide films for gas sensors  

Microsoft Academic Search

Metal oxide nanoparticles are interesting building blocks for realizing films for a number of applications that include bio- and -chemical sensing. In the present work TiO2 nanoparticles have been used for a self-assembling procedure to realize lined-up micro-patterned titanium oxide films. The high surface-to-volume ratio makes these structures suitable to adsorb gases. Morphological, compositional and structural characterization have been performed

A. Serra; E. Filippo; A. Buccolieri; M. Di Giulio; D. Manno

2009-01-01

84

Sensing characteristics of NiO thin films as NO 2 gas sensor  

Microsoft Academic Search

In this paper we present the results concerning the characterisation of nickel oxide thin films deposited by d.c. reactive magnetron sputtering. Different NiO thin films have been prepared by changing some deposition parameters, as the oxygen content in the reactive plasma and the sputtering mode (metal- or oxide-sputtering mode). The structure and surface morphology of the samples have been analysed

I. Hotovy; V. Rehacek; P. Siciliano; S. Capone; L. Spiess

2002-01-01

85

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

Microsoft Academic Search

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

Abhishek Sundararajan

2007-01-01

86

Nanostructured Refractory Metal Oxide Films Produced by a Pulsed Microplasma Cluster Source as Active Layers in Microfabricated Gas Sensors  

NASA Astrophysics Data System (ADS)

Cluster-assembled nanostructured films of refractory metal oxides were produced by supersonic cluster beam deposition (SCBD) using a pulsed microplasma cluster source (PMCS). The growth of nanostructured films takes place at room temperature on substrates exposed to nanoparticles beam. Soft landing and limited diffusion are peculiar characteristics of the deposition process, causing the film to grow according to a highly porous structure. We produced nanostructured Mo, W, and Nb oxide films and we characterized their crystal structure and film morphology at the nanoscale together with their gas sensing performances. The effect of thermal treatments on grain growth and morphology modification was particularly addressed in view of the use of the nanostructured layers in gas sensing applications on microfabricated platforms.

Barborini, Emanuele; Ducati, Caterina; Leccardi, Matteo; Bertolini, Giacomo; Repetto, Pietro; Milani, Paolo

2011-01-01

87

Gas-sensor properties of composite semiconductor films of substituted perylene and tin dioxide nanoparticles  

Microsoft Academic Search

Electrical conductivity of film samples of a composite constituted by a perylene derivative (3,4,9,10-perylenetetracarboxylic-dianhydride)\\u000a and SnO2 nanoparticles was studied in adsorption of vapors of ammonia, toluene, aqueous hydrogen peroxide, ethanol, and water. A model\\u000a of formation of the composite sample under study and a mechanism by which adsorbed molecules affect its electrical conductivity\\u000a are suggested.

A. S. Komolov; N. B. Gerasimova; E. V. Lazneva; S. A. Komolov; I. Z. Buzin

2010-01-01

88

Tin, Niobium and Vanadium mixed oxide thin films based gas sensors for chemical warfare agent attacks prevention  

Microsoft Academic Search

In this work we have studied the synthesis and characterization SnO2 thin films with varying Nb and V content for Sarin detection. As target molecule we used dimethyl methylphosphonate (DMMP), a Sarin nerve agent simulant. Nb and V oxides have been used because of their well-known catalytic properties. Results highlight that the proposed approach is suitable to develop sensors of

A. Ponzoni; E. Comini; G. Sberveglieri; I. Alessandri; E. Bontempi; L. E. Depero

2007-01-01

89

Zeolite-based discriminating gas sensors  

Microsoft Academic Search

The use of zeolites to enhance the discriminating power of solid state gas sensors is demonstrated. Screen printed tungsten trioxide (WO3) and chromium titanium oxide (CTO) thick films overlaid and admixed (CTO only) with different forms of zeolites are shown to give different and in some cases, enhanced responses to a variety of gases. We attempt to rationalise the noted

Sheena Dungey; Ayo Afonja; Dewi W. Lewis; Russell Binions; Ivan P. Parkin; Themis Paraskeva; David E. Williams

2008-01-01

90

Chemoresistive gas sensor  

DOEpatents

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

Hirschfeld, T.B.

1985-09-30

91

TiO2 Based Nanocrystalline Thin Film Gas Sensors Prepared by Ion-assisted Electron beam Evaporation  

Microsoft Academic Search

In this work, we develop TiO2 based nanocrystalline thin films prepared by ion-assisted e-beam evaporation process. N-type and p-type TiO2 gas-sensing layers have been deposited by doping with various metal oxide materials including WO3, MoO3, and NiOx. Structural and morphological characterization by means of AFM, SEM, and XRD reveal the thin film is nanocrystalline structure with fine grain of 10-30

A. Wisitsoraat; E. Comini; G. Sberveglieri; W. Wlodarski; A. Tuantranont

2007-01-01

92

Porous metal oxides as gas sensors.  

PubMed

Semiconducting metal oxides are frequently used as gas-sensing materials. Apart from large surface-to-volume ratios, well-defined and uniform pore structures are particularly desired for improved sensing performance. This article addresses the role of some key structural aspects in porous gas sensors, such as grain size and agglomeration, pore size or crack-free film morphology. New synthesis concepts, for example, the utilisation of rigid matrices for structure replication, allow to control these parameters independently, providing the opportunity to create self-diagnostic sensors with enhanced sensitivity and reproducible selectivity. PMID:17721888

Tiemann, Michael

2007-01-01

93

Room Temperature Gas Sensor with a High Sensitivity to Hydrogen Based on SnO2 Films Prepared by Photochemical Techniques  

NASA Astrophysics Data System (ADS)

Resistive gas sensors with a high sensitivity to hydrogen at room temperature were fabricated. SnO2 films were deposited by photochemical deposition using an SnSO4 solution, and Pd was doped by photochemical doping using a PCl2 solution. An interdigit Au electrode was formed, and then the samples were annealed in nitrogen atmosphere at various temperatures. The sensitivity and response speed depended on the annealing temperature. For the sample annealed at 200 °C, the conductivity increased by a factor of 104 upon exposure to 5000 ppm hydrogen within 1 min. The transient response was analyzed using a simple theoretical model. The sensor current was shown to be controlled by a Schottky barrier at grain boundaries, and the transient response was well fitted by a double-exponential function.

Ichimura, Masaya; Sueyoshi, Tetsuya

2009-01-01

94

Self-calibrating electrochemical gas sensor  

Microsoft Academic Search

A self-calibrating electrochemical gas sensor with an online supervision of the gas sensor's function, sensor's sensitivity and sensor's response time is presented. It leads to an online electrical recalibration and an early detection of an aging dependant sensor failure by detection of the value of sensor's electrochemical active area. Independent of the gas concentration to be measured, and without spoiling

L. Makadmini; M. Horn

1997-01-01

95

Radiation compensator for gas sensors  

SciTech Connect

A compensator device for providing direct and automatic correction of electrolytic gas sensor performance anomalies caused by exposure of the sensor to high levels of ionizing radiation. The compensator device, which compensates for changes in sensor performance while operating in a radiation field, provides an electromotive force which directly cancels that portion of the electromotive force developed by the active electrolytic gas sensor produced by the radiation rather than by presence of the gas. The compensating device is constructed in the same configuration as the active electrolytic sensor with the exception that the sensing electrode of the compensating device is not exposed to the sample gas environment. The sensor and compensator device are connected in a circuit such that their electromotive forces oppose one another, thereby determining the difference between the signals so that the radiation induced component is removed, and only the signal representing the partial pressure of gas remains. An alternate embodiment wherein the compensating signal is generated within the same sensor housing by the addition of one more electrode is also disclosed.

Rudek, F.

1985-02-05

96

Porous silicon ammonia gas sensor  

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

97

Investigation of gas sensors for cabin air quality monitoring  

Microsoft Academic Search

Car cabin air quality monitoring can effectively be analysed using metal oxide semiconducting (MOS) gas sensors. In this paper, commercially available gas sensors are compared with fabricated MoO3-TiO2 and MoO3- WO3 thin films. The laboratory tests showed that the MoO3 based sensors possessed comparable gas sensing properties. The MoO3(75%)-TiO2(25%) sensor has a response 74% higher relative to the best commercial

K. Galatsis; W. Wlodarski; K. Kalantar-Zadeh; A. Trinchi

2002-01-01

98

Gas sensing properties of WO 3 thick film for NO 2 gas dependent on process condition  

Microsoft Academic Search

The thick film sensor of tungsten oxide for NO2 gas detection was fabricated by changing the process conditions, which were firing temperature and annealing atmosphere. The origin of sensor property variation was interpreted by the characterization of crystallite size, specific surface area and microstructure. The degree of oxygen deficiency in the WO3 sensor also affected sensor properties and the optimum

Yong-Keun Chung; Mi-Hyang Kim; Woo-Sik Um; Hee-Soo Lee; Jun-Kwang Song; Sung-Churl Choi; Kang-Myung Yi; Myung-Jin Lee; Kyung-Won Chung

1999-01-01

99

Highly sensitive NH 3 sensor using Pt catalyzed silica coating over WO 3 thick films  

Microsoft Academic Search

Ammonia gas sensing properties of a single layer WO3 thick film and a double layer sensor structure having a supported catalyst on it have been investigated. The single layer sensor exhibited low response to NH3. An enhancement in gas response was achieved by doping WO3 with Pt, Pd or Au. Ammonia sensing properties of the WO3 thick film was improved

Vibha Srivastava; Kiran Jain

2008-01-01

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

MAPLE activities and applications in gas sensors  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

102

Prediction of quartz crystal microbalance gas sensor responses using a computational chemistry method  

Microsoft Academic Search

The characteristics of quartz crystal microbalance (QCM) gas sensors depend on the kinds of sensing films coated on their electrodes. Although it is essential, in an odor sensing system, to know the characteristics of various sensing films, they have not been characterized well enough to predict the sensor responses without any experiments. Hence, we tried to predict sensor responses using

K. Nakamura; T. Nakamoto; T. Moriizumi

1999-01-01

103

Development of a WO 3 thick-film-based sensor for the detection of VOC  

Microsoft Academic Search

A highly sensitive gas sensor for the detection of aromatic hydrocarbons has been developed using a WO3 thick film where Pd and Pt were applied as catalyst to a limited and most sensitive area of the film to the change in bulk resistance. WO3 thick films with different mean grain size and film thickness were prepared to investigate characteristics of

Keisen Kanda; Toru Maekawa

2005-01-01

104

Novel bi-functional film ceramic sensors for environmental applications  

Microsoft Academic Search

Two types of bi-functional film sensors have been developed for environmental applications. The first sensing device is based on n-type semiconducting metal oxide WO3 and is fabricated using thin-film surface microfabrication technology. It utilises gas chemisorption at elevated temperatures higher than 300°C as well as water physisorption on grain surfaces at temperatures lower then 150°C. Both humidity and particular pollution

Wenmin Qu; Wojtek Wlodarski; Ray Green; Mike Austin; K. Galatsis

1998-01-01

105

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

106

Soap film gas flowmeter  

SciTech Connect

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

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

1987-09-08

107

Intelligent gas-mixture flow sensor  

Microsoft Academic Search

A simple way to realize a gas-mixture flow sensor is presented. The sensor is capable of measuring two parameters from a gas flow. Both the flow rate and the helium content of a helium-nitrogen gas mixture are measured. The sensor exploits two measurement principles in combination with (local) information handling in an artificial neural network. An analysis of the measurement

Theo S. J. Lammerink; Fred Dijkstra; Zweitze Houkes; Joost van Kuijk

1995-01-01

108

Ozone sensors on the base of SnO 2 films deposited by spray pyrolysis  

Microsoft Academic Search

The gas-sensing properties of SnO2-based thin films designed for ozone detection are discussed in this paper. The influence of film characteristics on sensor performance is analyzed. SnO2 films with thickness 30–200nm were deposited by spray pyrolysis. The SnO2 films have a response to ozone that is quantitative and rapid and sufficient for use in ozone control and monitoring applications. Sensor

G. Korotcenkov; I. Blinov; M. Ivanov; J. R. Stetter

2007-01-01

109

CO2 gas sensitivity of sputtered zinc oxide thin films  

Microsoft Academic Search

For the first time, sputtered zinc oxide (ZnO) thin films have been used as a CO2 gas sensor. Zinc oxide thin films have been synthesized using reactive d.c. sputtering method for gas sensor applications, in the deposition temperature range from 130-153°C at a chamber pressure of 8?5 mbar for 18 h. Argon and oxygen gases were used as sputtering and

110

CO 2 gas sensitivity of sputtered zinc oxide thin films  

Microsoft Academic Search

For the first time, sputtered zinc oxide (ZnO) thin films have been used as a CO2 gas sensor. Zinc oxide thin films have been synthesized using reactive d.c. sputtering method for gas sensor applications,\\u000a in the deposition temperature range from 130–153°C at a chamber pressure of 8·5 mbar for 18 h. Argon and oxygen gases were\\u000a used as sputtering and

P. Samarasekara; N. T. R. N. Kumara; M. V. K. Perera

2007-01-01

111

Structure and Sensor Properties of Thin Ordered Solid Films  

PubMed Central

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

Soloducho, Jadwiga; Cabaj, Joanna; Swist, Agnieszka

2009-01-01

112

The stability of Pt heater and temperature sensing elements for silicon integrated tin oxide gas sensors  

Microsoft Academic Search

Good performance of alarm systems and environmental as well as industrial control methods requires an optimal operation of the gas sensors involved. An essential point related to this challenge is an accurate control of the sensor working temperature. Therefore, the stability of the Ti\\/Pt heater element used in tin oxide thin film gas sensors has been investigated. It turns out

H Esch; G Huyberechts; R Mertens; G Maes; J Manca; W De Ceuninck; L De Schepper

2000-01-01

113

Micro-sensor thin-film anemometer  

Microsoft Academic Search

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

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

1994-01-01

114

CO2 Selective Potentiometric Sensor in Thick-film Technology  

PubMed Central

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

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

2008-01-01

115

Thin film color sensors in multichannel technology  

Microsoft Academic Search

Color images are commonly captured with sensor arrays covered with a mosaic of RGB-filters. In spite of the enormous success of CMOS and CCD color cameras, one-chip color imagers suffer form color aliasing or color moire effects. In order to overcome these limitations we have realized color sensors based on vertical integrated thin film structures. The compete color information of

Dietmar Knipp; Helmut Stiebig; Heribert Wagner

2001-01-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

117

Plasma deposited polymers as gas sensitive films  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

118

Detection of Hydrogen Sulphide Gas Sensor Based Nanostructured Ba2CrMoO6 Thick Films  

Microsoft Academic Search

Nanocrystalline pure and doped Ba2CrMoO6, having an average crystallite size of 40 nm were synthesized by the sol-gel citrate method. Structural and gas-sensing characteristics were performed by using X-ray diffraction (XRD) and sensitivity measurements. The gas sensing properties to reducing gases like Hydrogen sulphide (H2S), liquefied petroleum gas (LPG), carbon monoxide (CO) and hydrogen gas (H2) were also discussed. The

A. V. Kadu; N. N. Gedam; G. N. Chaudhari

119

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

National Technical Information Service (NTIS)

Surface acoustic wave (SAW) sensors, which are sensitive to a variety of surface changes, have been widely used for chemical and physical sensing. The ability to control or compensate for the many surface forces has been instrumental in collecting valid d...

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

2000-01-01

120

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

Microsoft Academic Search

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

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

1997-01-01

121

Solution-processed ZnO-chemically converted graphene gas sensor  

Microsoft Academic Search

We report a solution-processed gas sensor based on vertically aligned ZnO nanorods (NRs) on a chemically converted graphene (CCG) film. The prepared sensor device effectively detected 2ppm of H2S in oxygen at room temperature. A high sensitivity of the gas sensor resulted from the growth of highly dense vertical ZnO NRs on the CCG film with numerous tiny white dots

Tran Viet Cuong; Viet Hung Pham; Jin Suk Chung; Eun Woo Shin; Dae Hwang Yoo; Sung Hong Hahn; Jeung Soo Huh; Gi Hong Rue; Eui Jung Kim; Seung Hyun Hur; Paul A. Kohl

2010-01-01

122

Micromachined polymer-based chemical gas sensor array  

Microsoft Academic Search

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

Frank Zee; Jack W. Judy

2001-01-01

123

Effects of NiO addition in WO 3-based gas sensors prepared by thick film process  

Microsoft Academic Search

NiO-doped WO3 thick films were prepared by the screen-printing technique. The microstructure and the electrical properties were investigated as functions of the amount of NiO, partial pressure of oxygen, concentration of NO2 and temperature. The grain growth is inhibited by the addition of NiO. The electrical conductance of undoped WO3 is high at low partial pressure of oxygen. The electrical

Whyoshup Noh; Yongjin Shin; Jintae Kim; Woosun Lee; Kwangjun Hong; Sheikh A. Akbar

2002-01-01

124

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

PubMed Central

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

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

2013-01-01

125

Solid electrolytes for gas sensors and fuel cells applications  

Microsoft Academic Search

Solid electrolytes are wider and wider used in electrochemical devices. They are of peculiar importance to gas sensors, membranes, pumps and fuel cells. The study of the conductivity of the thick film fast ion conducting systems (NASICON and BICUVOX) was carried out using ac impedance spectroscopy. Investigations of changes of electrolytes conductivity with temperature (Arrhenius plots) were carried out. Conducted

G Pasciak; K Prociow; W Mielcarek; B Gornicka; B Mazurek

2001-01-01

126

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

127

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

PubMed Central

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

Reiss, Sebastian; Hagen, Gunter; Moos, Ralf

2008-01-01

128

Polycrystalline-silicon microbridge combustible gas sensor  

NASA Astrophysics Data System (ADS)

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

Manginell, Ronald Paul

129

Combined-structure semiconductor gas sensor based on butane gas  

NASA Astrophysics Data System (ADS)

A new combined-structure semiconductor gas sensor based on butane gas is reported in this paper. The combined structure sensor is a gas sensor that is based on the complementary feedback principle. The sensor is composed of two sensitive materials A and B whose conductive types are the same. The materials A and B are all n-type materials. The results analysed from a theoretical viewpoint showed that the sensor had higher selectivity and better thermal stability when materials A and B satisfied certain conditions. According to the sensor's structure and meeting conditions, we prepared the combined-structure gas sensor for butane gas. The experimental results showed that they are consistent with theoretical analysis and can be applied to monitor and control leakage of butane gas.

Xinghui, Wu; Yude, Wang; Yanfeng, Li; Zhenlai, Zhou

2001-08-01

130

Platform for a hydrocarbon exhaust gas sensor utilizing a pumping cell and a conductometric sensor.  

PubMed

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 Ga(2)O(3) or doped SrTiO(3) 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

2009-09-18

131

Development of high sensitivity tin oxide based sensors for gas\\/odour detection at room temperature  

Microsoft Academic Search

An effort has been made to develop thick film tin oxide gas sensors which could detect various gases\\/odours at room temperature. To achieve this, the fabricated sensors were annealed in oxygen plasma for various durations. It was then found that, the room temperature sensitivity of such sensors was increased to about ten times as compared to the sensitivity of the

Roopali Srivastava; R Dwivedi; S. K Srivastava

1998-01-01

132

Solid State Gas Pressure Sensor.  

National Technical Information Service (NTIS)

The present invention relates to pressure sensors, and more, particularly, to thermoconductive vacuum pressure sensors. Thermoconductive vacuum transducers (sensors) measure pressure by monitoring the temperature of a heated wire filament in the transduce...

J. Halvis

1987-01-01

133

H2S sensors based on chemically treated SnO2:Pd thin films  

NASA Astrophysics Data System (ADS)

Preparation and characterization of gas sensors based on thin films of SnO2:Pd to monitor trace amounts of H2S in air are reported. Sensors have been exposed to 100% relative humidity to study the incorporation of hydroxyl group (-OH) in the film and its effects on gas sensing properties. Films have been subsequently treated with dilute sulphuric acid and characterized using different techniques such as X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, IR spectroscopy and electrical resistance measurements. IR studies reveal the presence of two types of hydroxyl groups (-OH) in the film; as 'free surface -OH' and hydrogen bonded -OH. The two types of -OH have been found to affect the gas sensing properties in different ways. Chemical treatment of films with dilute sulphuric acid has been found to improve the H2S sensing properties of the sensor by modifying the concentrations of the two types of hydroxyl groups.

Katti, V. R.; Kaur, Manmeet; Muthe, K. P.; Dua, A. K.; Gadkari, S. C.; Gupta, S. K.; Sahni, Vinod C.

2003-10-01

134

Hydrogen sensing characteristics of WO 3 thin film conductometric sensors activated by Pt and Au catalysts  

Microsoft Academic Search

The hydrogen gas sensing performance of platinum (Pt) and gold (Au) catalyst activated WO3 thin films were investigated. The WO3 thin films were deposited onto alumina transducers with platinum inter-digital electrodes using a R.F. magnetron sputtering. Exposure to hydrogen gas, results in changes in the carrier concentration and hence, the conductivity of the film. The sensors were found to exhibit

S. J. Ippolito; S. Kandasamy; K. Kalantar-zadeh; W. Wlodarski

2005-01-01

135

Chemical Gas Sensors Based On Nanowires  

Microsoft Academic Search

Chemical gas sensors based on nanowires can find a wide range of applications in clinical assaying, environmental emission control, explosive detection, agricultural storage and shipping, and workplace hazard monitoring. Sensors in the forms of nanowires are expected to have significantly enhanced performance due to high surface-volume ratio and quasi-one-dimensional confinement in nanowires. Indeed, chemical gas sensors based on nanowires with

Yaping Dan; Stephane Evoy; A. T. Charlie Johnson

2008-01-01

136

Microstructural effects in WO 3 gas-sensing films  

Microsoft Academic Search

The microstructure of 50 nm thick WO3 films used in surface acoustic wave (SAW) gas sensors was characterized by atomic force microscopy (AFM), X-ray diffraction (XRD) and conductivity measurements. The films were deposited by r.f. magnetron sputtering onto piezoelectric yz-cut LiNbO3 substrates at 200 °C and then subjected to annealing treatments in air. As-deposited films are amorphous, have an r.m.s.

M. D. Antonik; J. E. Schneider; E. L. Wittman; K. Snow; J. F. Vetelino; R. J. Lad

1995-01-01

137

A Large Scale Virtual Gas Sensor Array  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

138

Microstructure, kinetics and diffusion in tungsten trioxide thin film sensors  

NASA Astrophysics Data System (ADS)

The development of metal oxide films for gas sensing has largely depended on trial-and-error methods, since a direct relationship between film properties and gas response has yet to be firmly established. This relationship for the tungsten trioxide thin film system is the primary focus of this thesis. Deposition conditions were established for the synthesis of two types of thin (<1mu) having very different microstructures, denoted "epitaxial" and "polycrystalline", to investigate the role of microstructure on gas sensing properties. Both deposition conditions produce very dense, non-porous films. The microstructural characterizations show that "polycrystalline" films have many randomly oriented grains while "epitaxial" films have a single or small number of orientations with no clear grain boundaries. Epitaxial films have many lattice defects but they show no evidence of porosity and are nearly atomically smooth at the free surface. Thicker polycrystalline films are significantly rougher and show some unconnected pores. The lattice parameters measured for epitaxial films are consistent with the cubic bulk phase. The polycrystalline films appear to be either monoclinic or orthorhombic. A kinetic model for the gas sensing mechanism which accounts for surface reactions, adsorption limitations, surface and bulk defects, and which couples the surface processes to bulk defect diffusion is developed. The resulting coupled differential equations were solved by numerical methods. The model was successfully fit to experimental data for the electrical conductivity as a function of time during various gas ambient conditions. The time dependence of the data enables the identification of kinetic mechanisms and the magnitudes of kinetic constants. Within the limitations of the proposed model, the kinetic and transport properties of the two films showed relatively little difference. Gold is one of the catalytic metal additives used on WO3 sensing films. Its behavior during high temperature annealing is reported. Both SEM and TEM images showed that low gold coverages on WO3 films aggregate into larger particles at temperatures above 400°C. The particles increase in size and the number density decreases over time. Characterization of such processes is important for assessing long-term stability of sensors.

Legore, Lawrence Jay

2000-10-01

139

A digital hygrometer using a polyimide film relative humidity sensor  

Microsoft Academic Search

A digital hygrometer using a relative humidity sensor is developed. The sensor consists of a polyimide film spin-coated onto an Si substrate. The sensor model for signal processing, which describes the sensor capacitance in terms of relative humidity and temperature in closed form, is derived first. The interface appropriate for the sensor model, based on a relaxation oscillator, is designed

Hideo Shibata; Masahiro Ito; Masahiro Asakursa; K. Watanabe

1996-01-01

140

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.

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

2013-01-01

141

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

142

a Novel Method for Gas Sensors Characterization  

NASA Astrophysics Data System (ADS)

For E-nose applications, sensors are never specified towards the aroma chemicals, because it is difficult to generate a known amount of chemical vapours from a condensed phase. A method was developed, that allows the specification of gas sensors towards food samples, using a GC/sensors coupling. We have found the ADL lower than the GC-FID detector, and an unexpected response for E.V. Olive Oil.

Mielle, P.; Marquis, F.; Trivier, V.

2000-12-01

143

Smell selective gas sensor with modulation heating  

Microsoft Academic Search

We propose a new method to distinguish smells using an SnO2 gas sensor. We have measured the sensor response on heating up with several shaped voltages to improve its selectivity. The delay time of the response on heating by a triangular pulse voltage was different from that of alcoholic smells, and depended on the rise velocity of the triangular pulse.

Akira Fujimoto; Shuichi Okita

2004-01-01

144

Sensor of Ratios of Absolute Gas Pressures.  

National Technical Information Service (NTIS)

The article describes a sensor of ratios of absolute gas pressures containing elastic sensitive elements picking up pressures and acting on a compensation spring system transmitting the force onto a tensometric converter which for the purpose of improving...

G. I. Tyukel L. A. Pletnev

1967-01-01

145

Reversible Oxygen Gas Sensor Based On Electrochemiluminescence  

PubMed Central

A novel and robust oxygen gas sensor based on electrochemiluminescence of Ru(bpy)33+/+ ion annihilation in an ionic liquid is presented. Real-time detection of environmental oxygen concentration together with selective, sensitive and reversible performance is demonstrated.

Zhang, Lihua; Tsow, Francis

2013-01-01

146

Fabrication and characterization of micro-gas sensor for nitrogen oxides gas detection  

Microsoft Academic Search

WO3-based thin film micro-gas sensor was fabricated and the NOx gas sensing as well as electrical properties have been investigated. To obtain the optimal heat distribution, the structure of micro-hot plate was designed from the result of finite element simulation and was prepared by backside etching with KOH solution.The micro-hot plate was made out of N\\/O\\/N diaphragm with the thickness

Dae-Sik Lee; Jun-Woo Lim; Sang-Mun Lee; Jeung-Soo Huh; Duk-Dong Lee

2000-01-01

147

Hot-Film-Type Fuel-Flow Sensor.  

National Technical Information Service (NTIS)

A wide variety of flow sensors is available for applications including industrial flow meters and measuring instruments. The Mitsubishi hot-film-type fuel-flow sensor has been designed specifically for automotive applications. Fuel-flow values are derived...

H. Sato K. Tanimoto M. Bessho H. Arai Y. Tsuboi

1984-01-01

148

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

Microsoft Academic Search

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

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

2002-01-01

149

CO sensing with SnO 2 thick film sensors: role of oxygen and water vapour  

Microsoft Academic Search

The paper investigates the gas response of nanocrystalline SnO2 based thick film sensors upon exposure to carbon monoxide (CO) in changing water vapour (H2O) and oxygen (O2) backgrounds. The sensing materials were undoped, Pt- and Pd-doped SnO2. We found that in the absence of oxygen, the sensor signal (defined as the ratio between the resistance in the background gas, R0

S. H Hahn; N Bârsan; U Weimar; S. G Ejakov; J. H Visser; R. E Soltis

2003-01-01

150

Gas sensitivity measurements on NO{sub 2} sensors based on copper(II) tetrakis(n-butylaminocarbonyl)phthalocyanine LB films  

SciTech Connect

The NO{sub 2} gas-sensing characteristics of chemiresistors in the form of multilayered Langmuir-Blodgett films of a symmetrically substituted phthalocyanine, containing on the periphery four amidic groups -CONH-, have been studied. Floating layers were spread onto the water surface from a chloroform solution and were transferred onto both hydrophilic and hydrophobic quartz substrates using the vertical lifting method. Response and recovery times have been measured for different working temperatures at a fixed NO{sub 2} concentration. Dynamic response characteristics of the electrical conductance of the LB films to different NO{sub 2} concentrations, carried out in dry air, have shown a high sensitivity to concentrations of nitrogen dioxide smaller than 20 ppm at room temperature. All measurements have been carried out using coplanar configurations of the devices.

Capone, S.; Rella, R.; Siciliano, P. [Ist. per lo Studio di Nuovi Materiali per l`Elettronica, Lecce (Italy); Mongelli, S.; Valli, L. [Univ. Degli Studi di Lecce (Italy). Dipt. di Scienza dei Materiali

1999-03-02

151

Hydrogen gas sensor and method of manufacture  

DOEpatents

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

McKee, John M. (Hinsdale, IL)

1991-01-01

152

Integrated Micro-Machined Hydrogen Gas Sensor. Final Report  

SciTech Connect

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

Frank DiMeo, Jr.

2000-10-02

153

Sensor array for toxic gas detection  

DOEpatents

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

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

1987-01-01

154

Resistive Oxygen Gas Sensors for Harsh Environments  

PubMed Central

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

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

2011-01-01

155

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

2012-06-27

156

Monitoring of NH 3 gas by LB polypyrrole-based SAW sensor  

Microsoft Academic Search

Surface acoustic wave (SAW) devices have been fabricated and tested as sensors of NH3 in gaseous phase. Polypyrrole films, prepared by Langmuir-Blodgett (LB) technique, have been deposited onto the surface of SAW devices as gas absorbent layers. Simultaneous measurements of SAW phase velocity and attenuation have been carried out in order to investigate the sensing mechanisms. The sensor response shows

M. Penza; E. Milella; V. I. Anisimkin

1998-01-01

157

Model of Transient Response of Semiconductor Gas Sensors  

Microsoft Academic Search

The model of transient response of semiconductor gas sensor under modulation heating has been constructed successfully. The model consists of the heat conduction process from heater to the sensor surface, the reaction process on the sensor surface and diffusion process near the sensor surface to supply the inflammable gas. The calculated sensor response agreed well with experimental result under step

Akira Fujimoto; Takashi Kuwahara

2008-01-01

158

Development of carbon nanotube-based gas sensors for NOx gas detection working at low temperature  

NASA Astrophysics Data System (ADS)

Carbon nanotube (CNT)-based NOx gas sensors which can operate at room temperature were prepared on Al2O3 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 NO2 gases were measured. Resistance of the prepared CNT-based gas sensor decreased with increase of NO and NO2 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 NOx gas sensor from the experimental result.

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

2008-05-01

159

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

160

Crystalline structure, defects and gas sensor response to NO 2 and H 2S of tungsten trioxide nanopowders  

Microsoft Academic Search

Structural and NO2 and H2S gas-sensing properties of nanocrystalline WO3 powders are analysed in this work. Sensor response of thick-film gas sensors was studied in dry and humid air. Interesting differences were found on the sensor response between sensors based on 400 and 700°C-annealed WO3, what motivated a structural study of these materials. Crystalline structure and defects were characterised by

I. Jiménez; J. Arbiol; G. Dezanneau; A. Cornet; J. R. Morante

2003-01-01

161

Miniaturized gas ionization sensors using carbon nanotubes  

NASA Astrophysics Data System (ADS)

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

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

2003-07-01

162

Miniaturized gas ionization sensors using carbon nanotubes.  

PubMed

Gas sensors operate by a variety of fundamentally different mechanisms. Ionization sensors work by fingerprinting the ionization characteristics of distinct gases, but they are limited by their huge, bulky architecture, high power consumption and risky high-voltage operation. Here we report the fabrication and successful testing of ionization microsensors featuring the electrical breakdown of a range of gases and gas mixtures at carbon nanotube tips. The sharp tips of nanotubes generate very high electric fields at relatively low voltages, lowering breakdown voltages several-fold in comparison to traditional electrodes, and thereby enabling compact, battery-powered and safe operation of such sensors. The sensors show good sensitivity and selectivity, and are unaffected by extraneous factors such as temperature, humidity, and gas flow. As such, the devices offer several practical advantages over previously reported nanotube sensor systems. The simple, low-cost, sensors described here could be deployed for a variety of applications, such as environmental monitoring, sensing in chemical processing plants, and gas detection for counter-terrorism. PMID:12853951

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

2003-07-10

163

Prediction of Quartz Crystal Microbalance Gas Sensor Responses Using Grand Canonical Monte Carlo Method  

Microsoft Academic Search

\\u000a Our group has studied an odor sensing system using an array of Quartz Crystal Microbalance (QCM) gas sensors and neural-network\\u000a pattern recognition. In this odor sensing system, it is important to know the properties of sensing films coated on Quartz\\u000a Crystal Microbalance electrodes. These sensing films have not been experimentally characterized well enough to predict the\\u000a sensor response. We have

Takamichi Nakamoto

2009-01-01

164

Micro magnetic thin-film sensor using LC resonance  

Microsoft Academic Search

This paper reports the performance of a new micro magnetic thin-film magnetic field sensor which makes use of LC resonance of the sensor element as well as the impedance change due to the permeability change of the magnetic film. A large impedance change of 105% was achieved at a carrier frequency of 100 MHz. The large change was realized when

M. Takezawa; H. Kikuchi; K. Ishiyama; M. Yamaguchi; K. I. Arai

1997-01-01

165

Ultra-sensitive strain sensors based on piezoresistive nanographene films  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

166

ZnO thin film sensor  

Microsoft Academic Search

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

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

1998-01-01

167

Thermal Enzyme Sensor Utilizing Temperature-Sensitive Magnetic Thin Film  

Microsoft Academic Search

An approach to the biomagnetics of the thermal enzyme sensor (TES) utilizing a temperature-sensitive magnetic thin film (TMF) as a micromagnetic transducer is described. When an enzyme is infused into a chemical substance or a metabolite, an exothermic reaction occurs and the sensor absorbs a minute amount of heat, which causes a change of magnetization. Therefore, the sensor is suitable

Yoshimitsu Yachi; Kiyotaka Ito; Shigeki Chiba; Hiroshi Osada; Keiichi Sasaki; Masao Takahashi; Tsuneo Kubota; Kyoshiro Seki

2002-01-01

168

Characterization of Polymer Nanocomposite Thin Films Using Quartz Resonator Sensor  

Microsoft Academic Search

Thin films, especially polymer materials, as sensitive coating materials are wildly used in acoustic wave sensors for chemical and biological applications, and the responses of sensors commonly are regarded to the result of mass change. However, the mechanical properties of coating materials such as shear modulus also affect sensors in a more complicated way. It is therefore necessary to know

Lifeng Qin; Hongbin Cheng; Qing-Ming Wang

2006-01-01

169

Miniaturization of a biomedical gas sensor.  

PubMed

In a previous study, we concluded that a conductivity based PCO2 sensor is an attractive solution for early detection of ischemia and presented two design geometries. For organ surface measurements, the planar design was suitable but it was difficult to insert the sensor into the tissue. A cylindrical design solution was favored for insertion due to the large membrane contact area and easy placement in a medical catheter. Since the previous cylindrical prototype was large and could damage the tissue, a more miniaturized sensor was needed. In the current paper, we present a miniaturized sensor with an outer diameter of 1 mm. The applied technology for manufacturing the sensor was a combination of mechanical turning, excimer laser drilling and conventional molding technique. The materials applied were PEEK (polyetherether ketone), PI (polyimide) with gold layers and polysiloxane. The membrane had to be gas permeable while acting as a barrier for ion transport, and was made of polysiloxane and had a thickness of 100-150 microm. The miniaturized sensor was tested for calibration, response time, drifting and pressure sensitivity. The results show that the miniaturized PCO2 sensor is capable of rapid and stable measurements both in vitro and ex vivo. The result from this study will be applied for the industrial manufacturing of such a biomedical sensor as a clinical product. PMID:15712728

Mirtaheri, Peyman; Omtveit, Tore; Klotzbuecher, Thomas; Grimnes, Sverre; Martinsen, Orjan G; Tønnessen, Tor Inge

2004-12-01

170

Thick films of superconducting YBCO as magnetic sensors  

Microsoft Academic Search

Superconducting thick films of YBCO have been prepared successfully on MgO single-crystal substrate by a screen-printing method. A prototype magnetic field sensor has been made from these thick films and characterized using x-ray diffraction, scanning electron microscopy, and a magnetoresistance method. The microstructure of the YBCO thick film sensor was prepared in such a way so as to retain a

B A Albiss

2005-01-01

171

Carbon dioxide gas sensor derived from a 547-hole microstructured polymer optical fiber preform.  

PubMed

In this Letter, we report a carbon dioxide gas sensor having 547 pieces of thin-film modified capillaries, which are derived from a microstructured polymer optical fiber preform. Compared with the conventional absorption-based sensor, the monolithic polymer capillary waveguide arrays have better sensitivity, because the huge sensing surfaces, composed of 547 pieces of dye-indicator-doped porous ethyl cellulose layers, interact directly with the gas molecules. As far as we know, a gas sensor based on multichannel capillary waveguide arrays has not been reported before. PMID:20890356

Wang, Jian; Wang, Lili

2010-10-01

172

Micromachined metal oxide gas sensors: opportunities to improve sensor performance  

Microsoft Academic Search

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

Isolde Simon; Nicolae Bârsan; Michael Bauer; Udo Weimar

2001-01-01

173

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

174

Study on adhesion of thin film coatings of polypyrrole on glass substrate for mechanical durability of sensor devices  

NASA Astrophysics Data System (ADS)

Thin film coatings of polypyrrole have been extensively used as gas sensors in chemiresistors where the films are deposited on insulating substrates. These polypyrrole films have also been used as coatings to glass optical fiber as a chemo-chromic transducer for gas sensing. For long term mechanical durability of these sensing films, their adhesion to the substrate is very important. Adhesion between polypyrrole films and glass slide substrates is investigated for solution deposited polypyrrole films. The substrate surface is investigated in terms of addition of silane coupling agents and substrate surface roughness, for enhancement of the film substrate adhesion. The adhesion test is performed by the standard ASTM D - 4541 Pull-off Test Method. The films deposited on as-received slides are characterized for their electrical conductivity and optical transmission for their use in both chemiresistor and optical fiber sensor applications for nerve agent DMMP (di-methylmethylphosphonate) sensing.

Bansal, Lalitkumar; El-Sherif, Mahmoud

2004-09-01

175

Colorimetric blood-gas monitoring sensors  

NASA Astrophysics Data System (ADS)

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

Proctor, Keith J.; Seifert, George P.

1993-05-01

176

Construction of a Polyaniline Nanofiber Gas Sensor  

ERIC Educational Resources Information Center

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

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

2008-01-01

177

Construction of a Polyaniline Nanofiber Gas Sensor  

ERIC Educational Resources Information Center

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

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

2008-01-01

178

Ink-jet printed colorimetric gas sensors on plastic foil  

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

179

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

180

Nanocrystalline mesoporous SMO thin films prepared by sol gel process for MEMS-based hydrogen sensor  

NASA Astrophysics Data System (ADS)

MEMS based SnO2 gas sensor with sol gel synthesized mesoporous nanocrystalline (<10 nm) semiconductor thin (100~150 nm) film has been recently developed. The SnO2 nano film is fabricated with the combination of polymeric sol gel chemistry with block copolymers used for structure directing agents. The novel hydrogen sensor has a fast response time (1s) and quick recovery time (3s), as well as good sensitivity (about 90%), comparing to other hydrogen sensors developed. The improved capabilities are credited to the large surface to volume ratio of gas sensing thin film with nano sized porous surface topology, which can greatly increase the sensitivity even at relatively low working temperature. The gas sensing film is deposited onto a thin dielectric membrane of low thermal conductivity, which provides good thermal isolation between substrate and the gas-sensitive heated area on the membrane. In this way the power consumption can be kept very low. Since the fabrication process is completely compatible with IC industry, it makes mass production possible and greatly reduces the cost. The working temperature of the new sensor can be reduced as low as 100°C. The low working temperature posse advantages such as lower power consumption, lower thermal induced signal shift as well as safe detection in certain environments where temperature is strictly limited.

Gong, Jianwei; Fei, Weifeng; Seal, Sudipta; Chen, Quanfang

2004-01-01

181

Investigation of miniature CO 2 gas sensor based on NASICON  

Microsoft Academic Search

A miniature CO2 gas sensor based on NASICON (sodium super ionic conductor) thick film was fabricated. The solid-electrolyte NASICON material\\u000a was synthesized through an inorganic-reagent-based sol-gel method. The resulting materials were characterized by means of\\u000a X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). NASICON paste was coated on a piece of alumina substrate\\u000a attached to a platinum heater. Li2CO3-BaCO3 binary

Yu. He; B. Quan; B. Wang; Ch. Zhang; F. Liu

2007-01-01

182

Selective, pulsed CVD of platinum on microfilament gas sensors  

SciTech Connect

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

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

1996-05-01

183

Gas Sensors Based on Piezoelectric Micro-Diaphragm Transducer  

Microsoft Academic Search

We have fabricated high sensitive gas sensor based on piezoelectrically driven micro-diaphragm transducers. The micro-diaphragm transducer was fabricated using micro-electro-mechanical-system (MEMS) technique. The diol based sol-gel derived Pb(Zr0.52,Ti0.48)O3(PZT) film was used as a piezoelectric actuating layer. We have used the resonant frequency change of micro-diaphragm transducer upon mass increase as a sensing signal. The resonant frequency values were measured by

Jaichan Lee; Sanghun Shin; Jun-Kyu Paik; Nae-Eung Lee; Hyo-Derk Park; Jun-Shik Park

2005-01-01

184

A multiscale model for thin film AMR sensors  

NASA Astrophysics Data System (ADS)

AMR sensors are among the most widely deployed magnetic field sensors. In contrast to other technologies it has a simple structure and a low production cost. In this paper a multiscale modeling strategy is proposed to describe the performance of these sensors taking their specific features into account. The prediction of the behavior of a typical AMR thin film sensor has been studied and the results are compared to experimental measurements from the literature. The proposed micro-macro model offers an opportunity to investigate optimal material composition, crystallographic texture, film thickness or bias field level for specific applications.

Bartók, András; Daniel, Laurent; Razek, Adel

2013-01-01

185

Novel Nanostructured Zinc Oxide Ammonia Gas Sensor  

NASA Astrophysics Data System (ADS)

In the present study, we report a novel and easy technique to synthesize a ZnO nanostructured porous network using activated carbon (AC) that is used as a sensor material for an interacting gas at room temperature. The formation of the material was confirmed by XRD and HRTEM image. The porous nature of the synthesized ZnO could be used to incorporate a laser dyes into it which makes it more fluorescent material. Broad absorption/excitation band(s) in laser dye (Stilbene) helps to get it excited over a range and broad fluorescent emission that enhances the sensitivity on integration. The changes in the intensities of the absorption/emission spectra of sensitized ZnO on interaction with gas molecules could be used to fabricate a gas sensor working at room temperature.

Kumari, Surbhi; Sahare, P. D.; Gupta, Meenakshi; Kapoor, J. C.

2011-12-01

186

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.

187

Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring  

PubMed Central

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

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

2010-01-01

188

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

189

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

2011-12-01

190

Printable polythiophene gas sensor array for low-cost electronic noses  

NASA Astrophysics Data System (ADS)

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

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

2006-07-01

191

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

Microsoft Academic Search

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

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

2003-01-01

192

Taste Sensor Response Dependence on Metal Electrode using LB Film  

NASA Astrophysics Data System (ADS)

In this paper, sensor response by metal electrode and electrode surface condition was described. Single detecting film and multi metal electrodes were also examined. Metal electrode was changed from the conventional Ag and Au plate to Au, Ti and Cr evaporated metal films. To detect five basic taste substances, sensor parameters were defined by maximum voltage change and response time. Using these parameters five basic substances were clearly discriminated.

Takafuji, Satoshi; Akiya, Masashiro

193

High performance surface inspection method for thin-film sensors  

Microsoft Academic Search

Thin-film sensors for use in automotive or aeronautic applications must conform to very high quality standards. Due to defects that cannot be addressed by conventional electronic measurements, an accurate optical inspection is imperative to ensure long-term quality aspects of the produced thin-film sensor. In this particular case, resolutions of 1 mum per pixel are necessary to meet the required high

Volkmar Wieser; Stefan Larndorfer; Bernhard Moser

2007-01-01

194

Thin film polypyrrole\\/SWCNTs nanocomposites-based NH 3 sensor operated at room temperature  

Microsoft Academic Search

A PPY\\/SWCNTs nanocomposite-based sensor with relatively high sensitivity and fast response–recovery was developed for detection of NH3 gas at room temperature. The gas-sensitive composite thin film was prepared using chemical polymerization and spin-coating techniques, and characterized by Fourier transformed infrared spectra and field-emission scanning electron microscopy. The results reveal that the conjugated structure of the PPY layer was formed and

Nguyen Van Hieu; Nguyen Quoc Dung; Phuong Dinh Tam; Tran Trung; Nguyen Duc Chien

2009-01-01

195

Electrophysical properties of In 2 O 3 -and WO 3 -based gas-sensitive semiconducting films as sensors for unsymmetrical dimethylhydrazine in air  

Microsoft Academic Search

Some n-type semiconductor metal oxide sensors based on WO3 and In2O3 were studied in detecting unsymmetrical dimethylhydrazine (UDMH) vapors. The sensors are highly sensitive to the presence\\u000a of UDMH vapors in air at concentrations equal to or lower than the MPC. They have short response and relaxation times in detecting\\u000a UDMH vapors in air. It was found that, when ammonia

T. V. Belysheva; E. A. Kazachkov; L. P. Bogovtseva; V. N. Kubyshkin; V. M. Vokhontsev

2006-01-01

196

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

197

Calibration of thin film EMP sensors by AFWL Coaxial Chamber  

Microsoft Academic Search

Preliminary EMP calibration data on magnetic thin film current sensors has been obtained. The Air Force Weapon Lab's Coaxial Chamber was used as the EMP standard and a current pulse width of 40 ns was used. It was found that the sensitivity of the sensors can be increased by controlling the width of the 90° wall strip and that the

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

1976-01-01

198

ADVANCES IN THIN FILM SENSOR TECHNOLOGIES FOR ENGINE APPLICATIONS  

Microsoft Academic Search

Advanced thin film sensor techniques that can provide accurate surface strain and temperature measurements are being developed at NASA Lewis Research Center. These sensors are needed to provide minimally intrusive characterization of advanced materials (such as ceramics and composites) and structures (such as components for Space Shuttle Main Engine, High Speed Civil Transport, Advanced Subsonic Transports and General Aviation Aircraft)

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

199

Potentiometric Gas Sensors for Oxidic Gases  

Microsoft Academic Search

Solid electrolyte-based electrochemical devices combined with an auxiliary phase of oxyacid salt have, in this decade, emerged as new attractive sensors to detect oxidic gases of CO2, NO, NO2 and SO2. Various combinations of solid electrolytes and auxiliary phases as well as various new single or multi-component auxiliary phases have been exploited to improve the gas sensing properties and stability

Noboru Yamazoe; Norio Miura

1998-01-01

200

Polycrystalline-silicon microbridge combustible gas sensor  

Microsoft Academic Search

Catalytic, calorimetric gas detection is the most commonly used method for the detection of combustible gases below the lower-explosive limit (LEL). In this method, the heat of oxidation of a combustible species on a heated catalyst surface is detected by a resistance thermometer in proximity. Conventionally fabricated sensors suffer from high-power consumption (˜500 mW), slow thermal response (˜15 sec) and

Ronald Paul Manginell

1997-01-01

201

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

202

Modified extrinsic Fabry-Perot interferometric hydrogen gas sensor  

Microsoft Academic Search

We demonstrate the operation of an extrinsic Fabry-Perot interferometric sensor modified for the detection of hydrogen gas. The sensor is sputter coated with a 2 ?m layer of palladium metal which senses as the active sensing element. A theoretical description of the sensor is given, and its operation as a dynamically varying hydrogen sensor is described. A maximum sensitivity of

J. S. Zeakes; K. A. Murphy; A. Elshabini-Riad; R. O. Claus

1994-01-01

203

Thermal simulation and package investigation of wireless gas sensors microsystems  

Microsoft Academic Search

Gas sensor arrays based on metal oxides operating at high temperature are commonly used in many application fields. They can operate on different principles and each sensor may show very different responses to the individual gases in the environment. Data coming from the array can be merged for reliable gas detection. One point which is common to the different sensors

Andrea Paoli; Lucia Seminara; Daniele D. Caviglia; Alessandro Garibbo; Maurizio Valle

2009-01-01

204

Bacteriorhodopsin-based biochromic films for chemical sensors  

Microsoft Academic Search

Biochromic films based on bacteriorhodopsin (BR) have been investigated, with especial regard to the creation of long-lived miniature optical vapour sensors working in real time, and exploiting the good reversibility of BR. Films were fabricated by dispersing nanosize fragments of BR in a hydrophilic matrix (gelatin) and their distribution was investigated using electron microscopy. It was shown that the composite

J. P. Sharkany; S. O. Korposh; Z. I. Batori-Tarci; I. I. Trikur; J. J. Ramsden

2005-01-01

205

Laser Ablative Deposition of Polymer Films: A Promise for Sensor Fabrication  

NASA Astrophysics Data System (ADS)

There is a continuing interest in the use of polymer films as insulating components of sensors; a number of such films have been prepared by polymer sputtering or vacuum deposition processes involving gas phase pyrolysis/photolysis and by plasma decomposition of monomers. An attractive and rather new technique for the deposition of novel polymer films is IR laser ablation of polymers containing polar groups. We have recently studied this process with poly(vinyl chloride) (PVC), poly(vinyl acetate) (PVAc) and poly(vinyl chloride-co-vinyl acetate) P(VC/VAc) to establish its specific features and differences to conventional pyrolysis.

Blazevska-Gilev, Jadranka; Kup?ík, Jaroslav; Šubrt, Jan; Pola, Josef

206

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

207

Thick film CO 2 sensors based on Nasicon solid electrolyte  

Microsoft Academic Search

A planar miniaturised CO2 sensor based on thick films of Nasicon (Na+ conductor, Na3Zr2Si2PO12) electrolyte has been developed. The thick film was fabricated by screen printing Nasicon paste on an alumina substrate and then firing at 1543 K. scanning electron microscopy (SEM) analysis shows that the films achieved good densification, although reactions occur between Nasicon and alumina substrate, so conductivity

Ling Wang; R. V. Kumar

2003-01-01

208

Prospecting for toxic gases with gold film sensors  

SciTech Connect

This paper reports on a gold film sensor that detects such toxic chemicals as mercury in quantities of parts per million or parts per billion. The gold films, many times thinner than a human hair, are the key to the sensor, because gold - an inert, stable, fairly unreactive: element - is unaffected by interferences from aromatic hydrocarbons (sulfur dioxide, carbon monoxide and carbon dioxide) or water vapor. These gold film sensors are used for mercury detection in such places as hospitals, laboratories and sites where batteries, caustic soda, thermometers, fluorescent lights or photographic equipment are manufactured. The sensor also detects hydrogen sulfide, an application developed in 1982 for the control of odor and corrosion in paper and pulp mills, sewage treatment plants, oil refineries, and smelters.

Roy, K.A.

1988-12-01

209

Thin film-based optical fiber sensors  

Microsoft Academic Search

Optical thin films can be deposited on side- and end-face of optical fiber, if these films are sensitive to ambient environments, optical refractive index changes in thin films will finally result to variation of optical signals transmitted in the optical fiber. Here thin films work as sensitive elements and transducer to get response and feedback from environments, optical fiber here

Minghong Yang; Dai Jixiang; Wang Min; Xinling Tong; Desheng Jiang

2010-01-01

210

Humidity sensors based on polymer thin films  

Microsoft Academic Search

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

Y Sakai; Y Sadaoka; M Matsuguchi

1996-01-01

211

Electrochemical high-temperature gas sensors  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

212

The sensitivity to SO 2 of the SAW gas sensor with triethanolamine modified with boric acid  

Microsoft Academic Search

The sensitivity to SO2 of the SAW gas sensor coated with triethanolamine (TEA) modified with boric acid (H3BO3) (TEA and H3BO3 were mixed with a mole ratio 3:1) has been investigated. A better stability of the modified TEA film compared with that of TEA film was observed. Both the steady response ?f and the transient response (?f\\/?t)max varied linearly with

Shuji Qin; Zhongjie Wu; Zhongyue Tang; Yilin Song; Fanzhong Zeng; Dong Zhao

2000-01-01

213

Guanidinium-based potentiometric SO2 gas sensor.  

PubMed

An SO2 gas sensor was developed by using a hydrogen sulfite-selective electrode positioned behind a gas-permeable membrane (GPM). The hydrogen sulfite-selective electrode was prepared by incorporating a multicyclic guanidinium ionophore in a plasticized poly(vinyl chloride) membrane. This gas sensor presents important advantages over the conventional Severinghaus-type SO2 gas sensor that contains a pH electrode immersed in an internal solution behind the GPM. The Severinghaus gas sensor suffers interferences from weak acids that can cross the GPM as gases and change the pH of the internal solution. In contrast, in the proposed sensor, the excellent selectivity of the HSO3- electrode and the ability of the GPM to discriminate gaseous from nongaseous species combine to generate the most selective potentiometric SO2 gas sensor reported to date. PMID:9921127

Mowery, M D; Hutchins, R S; Molina, P; Alajarín, M; Vidal, A; Bachas, L G

1999-01-01

214

Carbon dioxide gas sensor using a graphene sheet  

Microsoft Academic Search

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

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

2011-01-01

215

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

216

Gas sensing properties of WO 3 doped rutile TiO 2 thick film at high operating temperature  

Microsoft Academic Search

A semiconductor gas sensor based on WO3 doped TiO2 having a rutile phase was fabricated on an Al2O3 substrate. The sensing film of the sensor was deposited by using screen printing. In order to enhance the sensitivity of the sensor, the sensing film was fabricated with a porous shape by high temperature heat treatment and the TiO2 layer was doped

Sung-Eun Jo; Byeong-Geun Kang; Sungmoo Heo; Soonho Song; Yong-Jun Kim

2009-01-01

217

Gas sensing properties of nanoparticle indium-doped WO 3 thick films  

Microsoft Academic Search

The gas sensing properties of pure and indium-doped nanoparticle WO3 thick films were studied. Sensors were prepared using commercial WO3 nanopowders and powder mixtures with different concentrations of In (1.5, 3.0 and 5.0wt.%). The gas sensing properties of the sensors to nitrogen dioxide, carbon monoxide, ammonia and ethanol were investigated. It was observed that the pure nanoparticle WO3 sensing layers

V. Khatko; E. Llobet; X. Vilanova; J. Brezmes; J. Hubalek; K. Malysz; X. Correig

2005-01-01

218

Polypyrrole thin films for gas sensors prepared by Matrix-Assisted Pulsed Laser Evaporation technology: Effect of deposition parameters on material properties  

Microsoft Academic Search

Thin films of polypyrrole (PPY) were prepared by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technology from two matrices: water and dimethylsulfoxide (DMSO). The deposition was carried out using a KrF excimer laser (laser fluence F ranged from 0.1 to 0.6 J cm?2). This work deals with optimization of two deposition parameters – laser fluence and number of pulses – for both matrices.

Dušan Kopecký; Martin Vr?ata; Filip Vysloužil; Vladimír Myslík; P?emysl Fitl; Ond?ej Ekrt; Pavel Mat?jka; Miroslav Jelínek; Tomáš Kocourek

2009-01-01

219

Xerogel Optical Sensor Films for Quantitative Detection of Nitroxyl  

PubMed Central

Xerogel films were synthesized via sol-gel chemistry to fabricate optical nitroxyl (HNO) sensors. Selective detection of HNO in solution was achieved by monitoring the rates of manganese(III) meso-tetrakis(4-sulfonatophenyl) porphyrinate (MnIIITPPS) reductive nitrosylation in the anaerobic interior of aminoalkoxysilane-derived xerogel films. Nitroxyl permeability in sensor films deposited in round-bottom 96-well plates was enhanced via incorporation of trimethoxysilyl-terminated poly(amidoamine-organosilicon) (PAMAMOS) dendrimers in the xerogel network. The selectivity of MnIIITPPS for HNO, the overall sensitivity, and the working dynamic range of the resulting sensors were characterized. The HNO-sensing microtitre plates were used to quantify pH-dependent HNO generation by the recently described HNO-donor sodium-1-(isopropylamino)diazene-1-ium-1,2-diolate (IPA/NO), and compare HNO-production efficiency between IPA/NO and Angeli’s salt, a traditional HNO-donor.

Dobmeier, Kevin P.; Riccio, Daniel A.; Schoenfisch, Mark H.

2013-01-01

220

Pd\\/PVDF thin film hydrogen sensor based on laser-amplitude-modulated optical-transmittance: dependence on H 2 concentration and device physics  

Microsoft Academic Search

A new all-optical laser-intensity-amplitude-modulated hydrogen sensor has been developed as a next-generation device to the earlier photopyroelectric hydrogen sensor. When modulated light is incident on a palladium thin film coated on a polymeric membrane, optical reflectance and transmittance signals are generated in photodiode detectors. When hydrogen gas comes into contact with the thin palladium film the gas is absorbed, altering

Andreas Mandelis; Jose A. Garcia

1998-01-01

221

Characterization of ?-Fe 2O 3 thin films deposited by atmospheric pressure CVD onto alumina substrates  

Microsoft Academic Search

There has been considerable interest in recent years in thin film gas-sensing materials. In comparison with conventional sintered bulk gas sensors, thin film gas-sensing materials have good sensitivity, optimum operating temperature and selectivity. Therefore, it is attractive to prepare thin film gas sensors so as to improve the characteristics of commercialized sintered body gas sensors. In addition, sensors based on

C. C. Chai; J. Peng; B. P. Yan

1996-01-01

222

Novel SnO 2-based gas sensors promoted with metal oxides for the detection of dichloromethane  

Microsoft Academic Search

A SnO2-based recoverable thick-film gas sensor was developed in this study for the detection of dichloromethane (DCM) of ppb level at 350°C. The response of the SnO2 sensor decreased gradually during multiple cycles of detection and recovery, while the response of the SnO2-based sensor, promoted simultaneously with Mo and Ni, was maintained during multiple cycles without deactivation. In particular, the

Soo Chool Lee; Ho Yun Choi; Soo Jae Lee; Woo Suk Lee; Jeung Soo Huh; Duk Dong Lee; Jae Chang Kim

2009-01-01

223

Near-infrared hollow waveguide gas sensors.  

PubMed

The development of a hollow core waveguide (HWG) gas sensor in combination with a fast and compact near-infrared (NIR) spectrometer is presented. The spectrometer operates in the spectral range of 1200-1400 nm and may thus be applied for the detection of gas-phase analytes providing NIR absorptions in that spectral window such as, e.g., methane. Since mid-infrared spectroscopy in combination with HWGs has already been successfully demonstrated for probing hydrocarbons in the gas phase, the present study investigates the achievable sensitivity in the NIR spectral regime. Methane has been selected as an exemplary analyte due to the fact that it shows strong absorption features in the mid-infrared (mid-IR) fingerprint area, but also overtone bands in the NIR. Since the HWG simultaneously serves as a miniaturized absorption gas cell and as an optical waveguide for NIR radiation, a compact yet optical and cost-efficient sensor device was established providing an interesting alternative in target sensing for mid-IR devices. The achieved limit of detection (LOD) was 5.7% (vol./vol.) methane for a 9.5 cm long HWG, 1.6% (vol./vol.) methane for a 39.1 cm long HWG, and 1.3% (vol./vol.) methane for a setup using a 77.4 cm long HWG, which provides the most practical HWG dimensions among the three investigated setups. Limit of quantitation (LOQ) values were calculated at 20.1% (vol./vol.) methane, 8.7% (vol./vol.) methane, and 5.6% (vol./vol.) methane, respectively. PMID:22054086

Frey, Corinna M; Luxenburger, Florian; Droege, Stefan; Mackoviak, Verena; Mizaikoff, Boris

2011-11-01

224

Characterization of the polypyrrole film-piezoelectric sensor combination.  

PubMed

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

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

1992-04-01

225

Gas sensing properties of defect-controlled ZnO-nanowire gas sensor  

Microsoft Academic Search

The effect of oxygen-vacancy-related defects on gas-sensing properties of ZnO-nanowire gas sensors was investigated. Gas sensors were fabricated by growing ZnO nanowires bridging the gap between two prepatterned Au catalysts. The sensor displayed fast response and recovery behavior with a maximum sensitivity to NO2 gas at 225 °C. Gas sensitivity was found to be linearly proportional to the photoluminescence intensity

M.-W. Ahn; K.-S. Park; J.-H. Heo; J.-G. Park; D.-W. Kim; K. J. Choi; J.-H. Lee; S.-H. Hong

2008-01-01

226

A micro channel integrated gas flow sensor for high sensitivity  

Microsoft Academic Search

In order to enhance measurement accuracy, a gas mass flow sensor integrated with micro channels is proposed in this paper. The uniqueness of this flow sensor is that there is thermal convection effect on two sides of diaphragm, which results in a more sensitive temperature distribution. The temperature characteristics of the novel flow sensor are simulated at different flow rates,

Bolin Yu; Zhiyin Gan; Shu Cao; Jingping Xu; Sheng Liu

2008-01-01

227

Development of bulk-scale and thin film magnetostrictive sensor  

NASA Astrophysics Data System (ADS)

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

Liang, Cai

228

Pd Nanoparticles and Thin Films for Room Temperature Hydrogen Sensor  

PubMed Central

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

2009-01-01

229

Superconducting iridium thin films as transition edge sensors  

NASA Astrophysics Data System (ADS)

Transition edge sensors are the detectors of choice for a wide range of applications; from dark matter search, neutrino search, to cosmic radiation detection from near infrared to millimeter wavelengths. We are developing transition edge sensors using superconducting iridium thin films and we are proposing their use for future dark matter and neutrino search experiments. Our Ir films are deposited using an radio frequency (RF) magnetron sputtering and photolithographic techniques and measured using an adiabatic refrigerator capable of reaching temperatures of a few tens of mK. This thesis presents a detailed description of superconducting iridium thin films from the fabrication process to the characterization of the film properties at room temperature and low temperature. Alternative options for the bias circuit used to read out the TES signals will be discussed, we are proposing the use of RLC resonant circuits and transformers instead of SQUIDS.

Bogorin, Daniela F.

230

Detection of nitrogen dioxide using mixed tungsten oxide-based thick film semiconductor sensor  

Microsoft Academic Search

The thick film semiconductor sensor for NO2 gas detection was fabricated by screen-printing method using a mixed WO3-based as sensing material. The sensing characteristics, such as response time, response linearity, sensitivity, working range, cross sensitivity, and long-term stability were further studied by using a WO3-based mixed with different metal oxides (SnO2, TiO2 and In2O3) and doped with noble metals (Au,

P.-G Su; Wu Ren-Jang; Nieh Fang-Pei

2003-01-01

231

MoO 3 and WO 3 based thin film conductimetric sensors for automotive applications  

Microsoft Academic Search

Un-doped semiconducting oxides suitable for automotive gas sensor applications have been studied in this work. Thin films of MoO3 and WO3 were fabricated by ion beam deposition on alumina substrates with gold interdigitated electrodes. The process pressure inside the deposition chamber was 1.6 × 10-4 Torr. The oxygen to argon ratio in the secondary plasma was maintained at 5:5 sccm.

A. K. Prasad; P. I. Gouma

2003-01-01

232

Measurement of Trace Levels of Atmospheric Sulfur Dioxide with a Gold Film Sensor  

Microsoft Academic Search

The mercury translation principle, wherein S(IV) reacts with Hg(l) to produce Hg(ll) and Hg(O), was utilized to measure trace levels of SO2 with a conductometric gold film sensor. One approach involved impregnated glass fiber filters containing mercurous salts. The second and more successful approach utilized a porous membrane reactor where the reaction occurs in the interstitial liquid-gas interface as the

Yosiharu Hisamatsu; Liu Ping; Purnendu K. Dasgupta

1989-01-01

233

Tunable thin film filters for low cost optical sensors from 0.8 - 10 mum  

Microsoft Academic Search

Aegis Semiconductor pioneered the use of tunable thin films based on thermo-optic effects in amorphous semiconductors, with original application to fiber optic telecom networks at 1.5 mum. In this paper we describe an extension of this technology to longer wavelengths in the mid-infrared to produce a new family (named Firefly(tm)) of gas and chemical sensors based on narrowband, micro-tunable, mid-infrared

Lawrence Domash

2005-01-01

234

Sensoring hydrogen gas concentration using electrolyte made of proton  

SciTech Connect

Hydrogen gas promises to be a major clean fuel in the near future. Thus, sensors that can measure the concentrations of hydrogen gas over a wide dynamic range (e.g., 1 99.9%) are in demand for the production, storage, and utilization of hydrogen gas. However, it is difficult to directly measure hydrogen gas concentrations greater than 10% using conventional sensor [1 11]. We report a simple sensor using an electrolyte made of proton conductive manganese dioxide that enables in situmeasurements of hydrogen gas concentration over a wide range of 0.1 99.9% at room temperature.

Ueda, Yoshikatsu [Kyoto University, Japan; Kolesnikov, Alexander I [ORNL; Koyanaka, Hideki [Kyoto University, Japan

2011-01-01

235

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

236

Wall shear stress hot film sensor for use in gases  

NASA Astrophysics Data System (ADS)

The purpose of this work is to present the construction and characterization of a wall shear stress hot film sensor for use in gases made with MEMS technology. For this purpose, several associated devices were used, including a constant temperature feedback bridge and a shear stress calibration device that allows the sensor performance evaluation. The sensor design adopted here is simple, economical and is manufactured on a flexible substrate allowing its application to curved surfaces. Stationary and transient wall shear stress tests were carried on by means of the calibration device, determining its performance for different conditions.

Osorio, O. D.; Silin, N.

2011-05-01

237

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

238

Development of tactile sensor using thin film made of poly-urethane and its characterization  

Microsoft Academic Search

A novel capacitive tactile sensor using a gelled poly-urethane thin film is proposed in this paper. In previous studies, capacitive tactile sensors have an air gap between two electrodes in order to enhance sensitivity of the sensors. On the other hand, there is only poly-urethane thin film between the electrodes in this study. However, sensitivity of this sensor is higher

MASATO SUZUKI; SHOTA IWAMOTO; TATSUYA ISHIMARU; TAKASHI TOUGE; SEIJI AOYAGI

2010-01-01

239

Oxygen sensor for monitoring gas mixtures containing hydrocarbons  

DOEpatents

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

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

1996-01-01

240

Oxygen sensor for monitoring gas mixtures containing hydrocarbons  

DOEpatents

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

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

1996-03-12

241

Frequency counting interrogation techniques applied to gas sensor arrays  

Microsoft Academic Search

This paper presents a simple, elegant interrogation technique for conducting polymer gas sensor arrays which takes advantage of their resistive and capacitive properties. To accomplish this, a four-channel Wien bridge oscillator system has been designed and constructed in which the conducting polymer sensor forms one of the arms of the bridge circuit. As gas or odour molecules adsorb and desorb

M. E. H. Amrani; P. A. Payne; R. M. Dowdeswell; A. D. Hoffman

1999-01-01

242

Robust designed capacitive gas pressure sensor for harsh environment  

Microsoft Academic Search

In this study, a gas pressure sensing device based on stainless steel diaphragm and titanium substrate for use at harsh environment is presented. To illustrate these principles, array type capacitive gas pressure sensors based on a stainless steel and titanium have been designed and fabricated. For the fabrication of the sensor, both of bulk and surface micromachined techniques are used

Heung-Shik Lee; Chongdu Cho; Sung Pil Chang

2009-01-01

243

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

Code of Federal Regulations, 2013 CFR

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

2013-04-01

244

Flexible piezoelectric pressure sensors using oriented aluminum nitride thin films prepared on polyethylene terephthalate films  

NASA Astrophysics Data System (ADS)

We have investigated the high sensitive piezoelectric response of c-axis oriented aluminum nitride (AlN) thin films prepared on polyethylene terephthalate (PET) films. The AlN films were deposited using a radio frequency magnetron sputtering method at temperatures close to room temperature. The c axes of the AlN films were perpendicularly oriented to the PET film surfaces. The sensor consisting of the AlN and PET films is flexible like PET films and the electrical charge is linearly proportional to the stress within a wide range from 0 to 8.5 MPa. The sensor can respond to the frequencies from 0.3 to over 100 Hz and measures a clear human pulse wave form by holding the sensor between thumb and middle finger. The resolution of the pulse wave form is comparable to a sphygmomanometer at stress levels of 10 kPa. We think that the origin of the high performance of the sensor is the deflection effect, the thin thickness and high elastic modulus of the AlN layer, and the thin thickness and low elastic modulus of the PET film.

Akiyama, Morito; Morofuji, Yukari; Kamohara, Toshihiro; Nishikubo, Keiko; Tsubai, Masayoshi; Fukuda, Osamu; Ueno, Naohiro

2006-12-01

245

CuO\\/SnO 2 thin film heterostructures as chemical sensors to H 2S  

Microsoft Academic Search

CuO\\/SnO2 heterostructures as well as SnO2(CuO) polycrystalline films have been studied for H2S sensing. Gas sensing properties of these materials have been compared in conditions: 25–300 ppm H2S in N2 at 100–250°C. A shorter response time of the heterostructures as compared to that of the SnO2(CuO) films has been found. It is suggested that the improvement of dynamic sensor properties

R. B Vasiliev; M. N Rumyantseva; N. V Yakovlev; A. M Gaskov

1998-01-01

246

The gas-sensing properties of WO3-x thin films deposited via the atmospheric pressure chemical vapour deposition (APCVD) of WCl6 with ethanol  

Microsoft Academic Search

The use of the APCVD reaction of WCl6 with ethanol to produce tungsten oxide films (3600-6700 nm thick) for use as gas sensors is presented. The response of these films to varying concentrations of ethanol and NO2 at varying temperatures has been examined. A comparison of the CVD sensors to a thick film (~60 µm) screen-printed sensor has shown that

Sobia Ashraf; Christopher S. Blackman; Simon C. Naisbitt; Ivan P. Parkin

2008-01-01

247

Designing an amperometric thick-film microbial BOD sensor  

Microsoft Academic Search

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

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

2000-01-01

248

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

249

Single Carbon Nanotube Based Ion Sensor for Gas Detection  

Microsoft Academic Search

This paper presents a new method for carbon nanotube based gas sensing. Instead of sensing the gas directly, the gas molecules are first ionized and then the ionized molecules are sensed by the single carbon nanotube based ion sensor. The adsorption of ionized gas molecule on the carbon nanotube surface introduces electrons into the material and consequently changes the current

Jiangbo Zhang; Ning Xi; Hoyin Chan; Guangyong Li

2006-01-01

250

Measurements of Compressibility Effects in Stepped Thrust Gas Film Bearings  

Microsoft Academic Search

Hydrodynamic gas film bearings are used for supporting high-speed, lightly loaded rotating machinery. Stepped-type gas film bearings are often used for such machinery because of theïr simple structure, high stability and load carrying capacity. This paper describes the measurements of compressibility effects on the static and dynamic characteristics of stepped thrust gas film bearings. In the experiments, the minimum film

H. Hashimoto; M. Ochiai

1999-01-01

251

The utilization of thin film sensors for measurements in turbomachinery  

NASA Astrophysics Data System (ADS)

Sensor features and data analysis principles for thin films used as pressure and temperature transducers for flowfield measurements in turbomachinery are described. The devices were developed to collect data without affecting the flowfield around fixed and rotating turbine blades. The concept has been extended to thermal fluxmeters for measuring convection by the thermoelectric effect and to measuring the aerodynamics of boundary layer flows by exploiting temperature-induced changes in the resistivity of certain metals. The films have a maximum thickness of 80 microns, can be integrated into the walls of the area under investigation by vapor phase deposition, and require adhesive layers of only 2-4 microns. Numerical models are furnished for solid and gaseous dielectric sensor films for pressure measurements and for relating data from a thermal fluxmeter to temperature fields of a flow.

Bruere, A.; Portat, M.; Godefroy, J. C.; Helias, F.

252

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

253

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

NASA Astrophysics Data System (ADS)

Multi-walled carbon nanotubes (MWCNTs)-polymer composite-based hybrid sensors were fabricated and integrated into a resistive sensor design for gas sensing applications. Thin films of MWCNTs were grown onto Si/SiO2 substrates via xylene pyrolysis using the chemical vapor deposition technique. Polymers like PEDOT:PSS and polyaniline (PANI) mixed with various solvents like DMSO, DMF, 2-propanol and ethylene glycol were used to synthesize the composite films. These sensors exhibited excellent response and selectivity at room temperature when exposed to low concentrations (100 ppm) of analyte gases like NH3 and NO2. The effect of various solvents on the sensor response imparting selectivity to CNT-polymer nanocomposites was investigated extensively. Sensitivities as high as 28% were observed for an MWCNT-PEDOT:PSS composite sensor when exposed to 100 ppm of NH3 and - 29.8% sensitivity for an MWCNT-PANI composite sensor to 100 ppm of NO2 when DMSO was used as a solvent. Additionally, the sensors exhibited good reversibility.

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

2011-05-01

254

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

PubMed

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

Alexy, Marcin; Voss, Gundula; Heinze, Jürgen

2005-06-29

255

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

Microsoft Academic Search

The paper describes the results of our studies on material processing, design, fabrication and characterization of two kinds of multi-functional solid state sensor in thick-film and thin-film technology. The first sensing device is based on Cr3+ doped perovskite ferroelectric metal oxide Ba1-xSrxTiO3 (x = 0-1) and is fabricated using thick-film technology. Thick films of porous Ba1-xSrxTiO3 exhibit a change in

Wenmin Qu; Ray Green; Mike Austin

2000-01-01

256

Designing an amperometric thick-film microbial BOD sensor.  

PubMed

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

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

2000-10-01

257

Structure and gas-sensitive properties of WO 3–Bi 2O 3 mixed thick films  

Microsoft Academic Search

WO3–Bi2O3 mixed screen-printed thick films with various Bi2O3 contents (3–50 wt.%) have been studied as a promising sensitive material for NO gas sensors. It has been revealed that the Bi2O3 influence on gas-sensitive electrical properties of the mixed thick films is ambiguous and depends strongly on Bi2O3 content. WO3–Bi2O3 (3 wt.%) thick films are more sensitive to NO than pure

A. A Tomchenko

2000-01-01

258

Neutral cuprous complexes as ratiometric oxygen gas sensors.  

PubMed

Four neutral mononuclear Cu(I) complexes, [Cu(pyin)(PPh(3))(2)] (1a), [Cu(pyin)(DPEphos)] (1b), [Cu(quin)(PPh(3))(2)] (2a) and [Cu(quin)(DPEphos)] (2b) (Hpyin = 2-(2-pyridyl)indole, Hquin = 2-(2-quinolyl)indole and DPEphos = bis(2-(diphenylphosphino)phenyl)ether) have been synthesized. X-Ray crystal structure analysis revealed that the central Cu(I) ion in all complexes is in a distorted tetrahedral coordination environment. All four complexes display the typical metal-to-ligand charge transfer (MLCT) absorption band at 371, 363, 413 and 402 nm, respectively. No emission was observed from any complexes in the solid state due to triplet-triplet annihilation. However, the complexes show unusual dual-emission originating from intraligand charge-transfer (ILCT) and MLCT transitions, when dispersed in a rigid matrix (e.g. PMMA) or in frozen CH(2)Cl(2). The oxidation potential of Cu(I)/Cu(II) in these neutral complexes, ?0.5 V (vs. Ag/AgCl), is lower than those of cationic Cu(I) complexes. Films containing 10 wt% of these complexes in PMMA shows ratiometric fluorescent oxygen gas sensing property with a response ratio of 0.3-3.2 and response time of 3-4 s. Complex 2b acts as a ratiometric oxygen gas sensor with good reversibility through energy and electron transfer mechanisms under the loss of a counteranion. PMID:22134379

Liu, Xiaohui; Sun, Wei; Zou, Luyi; Xie, Zhiyuan; Li, Xiao; Lu, Canzhong; Wang, Lixiang; Cheng, Yanxiang

2011-12-02

259

Gas Sensor Based on Chalcohalide AgI-Containing Glasses  

NASA Astrophysics Data System (ADS)

Layered Ge-S-AgI material was used as a sensitive layer in cantilever gas sensors. The proposed sensor system was exposed to different vapour analytes: water, acetone, ammonia. The sensor studied works on the principle of a resonance microbalance and showed the best response to ammonia vapours. The chemisorbed ammonia on the surface of the exposed material caused an increased sensitivity towards water.

Monchev, Boris; Petkova, T.; Popov, Cyril; Petkov, Plamen

260

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

261

Metallic spintronic thin film as a hydrogen sensor  

NASA Astrophysics Data System (ADS)

We investigate the ferromagnetic resonance response of palladium-cobalt bi-layer thin films to hydrogen charging at atmospheric pressure. We find that hydrogen absorption by the palladium capping layer results in the narrowing and shifting of the ferromagnetic resonance line of the underlying cobalt. We explain the observed phenomena as originating from reduction in the spin pumping effect and from variation in the magnetic anisotropy of the cobalt layer through an interface effect. The shift of the resonance frequency or field is the easiest to detect. We utilize this to demonstrate functionality of the bi-layer film as a hydrogen sensor.

Chang, Crosby S.; Kostylev, Mikhail; Ivanov, Eugene

2013-04-01

262

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

Microsoft Academic Search

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

Paisan Setasuwon

263

Aluminum-doped TiO 2 nano-powders for gas sensors  

Microsoft Academic Search

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

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

2007-01-01

264

Catalytic combustion type hydrogen gas sensor using TiO 2 and UV-LED  

Microsoft Academic Search

A thick film catalytic gas sensor operable at a temperature of 82°C in the presence of UV-LED (ultra violet-light emitting diode) has been developed to measure hydrogen concentration in the range of 0.5–5%. The sensing material as a combustion catalyst consists of TiO2 (5wt%) and Pd\\/Pt (20wt%) supported on ?-Al2O3 powder. The reference material to compensate the heat capacity of

Chi-Hwan Han; Dae-Woong Hong; Sang-Do Han; Jihye Gwak; Krishan C. Singh

2007-01-01

265

Thermal analysis of silicon carbide based micro hotplates for metal oxide gas sensors  

Microsoft Academic Search

This paper reports on the thermal analysis of a novel micro hotplate design for metal oxide gas sensors. The hotplate is a 500?m×500?m square shaped membrane made of 2?m thick polycrystalline 3C–SiC on a silicon substrate suspended by four legs. The membrane is heated by an on chip platinum thin film heater. For reasons of a short response time and

G. Wiche; A. Berns; H. Steffes; E. Obermeier

2005-01-01

266

Thick-film force, slip and temperature sensors for a prosthetic hand  

Microsoft Academic Search

Thick-film static and dynamic force sensors have been investigated for their suitability to measure the grip forces exerted upon an object held by a prosthetic hand, and to detect and correspondingly react to the possible slip of a gripped item. The static force sensors exploit the piezoresistive characteristics of commercially available thick-film pastes whilst the dynamic slip sensors utilize the

A Cranny; D P J Cotton; P H Chappell; S P Beeby; N M White

2005-01-01

267

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

PubMed Central

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

Sadek, Khaled; Moussa, Walied

2007-01-01

268

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 (ZrOâ) ceramic electrolyte

Takami

1988-01-01

269

An electrochemical sensor for determining elemental iodine in gas media  

SciTech Connect

The possibility of using solid-electrolyte Ag, AgI/AgI/Au cells as sensors for determining the concentration of elemental iodine in gas media is investigated. It is established that the sensor parameters are independent of oxygen content and radiation dose at different relative humidities.

Goffman, V.G.; Shaimerdinov, B.U.; Kotelkin, I.M. [Institute of New Chemical Problems, Moscow (Russian Federation)] [and others

1993-12-01

270

Study of deposition of gas sensing films on quartz crystal microbalance using an ultrasonic atomizer  

Microsoft Academic Search

A novel method for depositing gas sensing films on quartz crystal microbalance electrodes was developed. The method is based on the production of a fine mist of the solution with the sensing material by means of an ultrasonic atomizer. The mist is transported by a dry air flow to the quartz substrate allowing its deposition. The responses of the sensors

Severino Muñoz-Aguirre; Takamichi Nakamoto; Toyosaka Moriizumi

2005-01-01

271

Adsorption of Water on Surface Acoustic Wave Gas Sensors.  

National Technical Information Service (NTIS)

Surface acoustic wave sensors (SAWS) respond to mass adsorbed onto chemically specific coatings put upon the acoustic wave transmission path. Target gas response is perturbed by naturally present atmospheric water vapor. This work measured the response of...

C. G. Fox J. F. Adler

1988-01-01

272

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

273

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

Microsoft Academic Search

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

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

1998-01-01

274

Design of micro-sensor-array detector for toxic gas  

Microsoft Academic Search

To quickly measure the trace concentration of the single component toxic gas (e.g. sarin), a micro-array toxic gas detector is designed. A 3 x 3 gas sensor array with metalloporphyrins as sensitive materials is introduced. A micro-capsule that can be easy to be loaded and unloaded is designed for the gas reaction. A fiber-array optical path is designed, which is

Hai-Yang Liao; Peng Tian

2010-01-01

275

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

276

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

277

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

278

Design and modeling of metal oxide gas sensors  

NASA Astrophysics Data System (ADS)

Detailed theoretical models are presented, and used to facilitate the design of industrial metal oxide gas sensors. By modeling both the sensing mechanisms and the conduction process, these methods optimize the sensitivity and selectivity. A phenomenological approach to the operation of metal oxide gas sensors, the Integrated Reaction Conduction (IRC) model, is introduced. The IRC model consolidates the surface reaction kinetics and electrical conduction through the granular sensor microstructure. A simple relation is established between the sensing mechanism reaction energies and the sensing behavior of n-type oxide sensors. The adsorption and oxidation reaction energies for anatase-phase based TiO2 sensors are extracted from comparisons with experimental data. By predicting the effects of dopants, temperature, and sintering on the sensor response, the IRC model foretells improvement of the sensitivity and other gas sensor properties. The depletion width prior to reducing gas exposure in an n-type metal oxide sensor is calculated by combining the known defect chemistry and the various phenomena determining electron depletion near the oxide surface. These include the charged surface of adsorbed oxygen ions, dopant segregation, and ionic defect accumulation. The sensor response is found to enhance if the depletion width is comparable to the grain size. Affecting the initial depletion width via dopants or ionic defect equilibration provides an alternate route towards sensor response optimization. The Polychromatic Percolation Model (PPM) is introduced, and facilitates the design of a selective n/p composite sensor by predicting the sensor response as a function of the n-type/p-type composition. Conduction through an n-type/p-type composite containing randomly distributed and oriented grains is characterized as a percolation phenomenon, where the overall resistance of the material combines contributions from n-type and p-type pathways. The composite microstructure governs the relative fraction of each pathway type and its respective percolation threshold, while the effective resistance through each pathway is calculated using experimentally measured resistances of single-phase n-type and p-type materials. PPM model calculations match the experimentally measured response of an anatase/rutile TiO2 composite gas sensor, and the conductivity of a ZnO/CuO n/p composite. Using the predictions of the PPM model, a selective n/p composite sensor may be designed.

Chwieroth, Brian Stewart

279

Novel fabrication of an SnO(2) nanowire gas sensor with high sensitivity.  

PubMed

We fabricated a nanowire-based gas sensor using a simple method of growing SnO(2) nanowires bridging the gap between two pre-patterned Au catalysts, in which the electrical contacts to the nanowires are self-assembled during the synthesis of the nanowires. The gas sensing capability of this network-structured gas sensor was demonstrated using a diluted NO(2). The sensitivity, as a function of temperature, was highest at 200?°C and was determined to be 18 and 180 when the NO(2) concentration was 0.5 and 5 ppm, respectively. Our sensor showed higher sensitivity compared to different types of sensors including SnO(2) powder-based thin films, SnO(2) coating on carbon nanotubes or single/multiple SnO(2) nanobelts. The enhanced sensitivity was attributed to the additional modulation of the sensor resistance due to the potential barrier at nanowire/nanowire junctions as well as the surface depletion region of each nanowire. PMID:21817675

Choi, Young-Jin; Hwang, In-Sung; Park, Jae-Gwan; Choi, Kyoung Jin; Park, Jae-Hwan; Lee, Jong-Heun

2008-02-11

280

Chemical sensors  

SciTech Connect

This review of chemical sensors contains the following topics of interest: books and reviews; reviews of sensors by their type; fabrication and selectivity; data processing; thermal sensors; mass sensors (fabrication, gas sensors, and liquid sensors); electrochemical sensors (potentiometric sensors, amperometric sensors, and conductometric sensors); and optical sensors (fabrication, liquid sensors, biosensors, and gas sensors). 795 refs., 1 tab.

Janata, J.; Josowicz, M.; DeVaney, D.M. (Pacific Northwest Lab., Richland, WA (United States))

1994-06-15

281

Thin film stress studies using microcantilevers and microcantilever sensors  

Microsoft Academic Search

Adsorption-induced and absorption-induced stresses on coated microcantilevers can produce bending, which can be related to gas or vapor concentration for sensing applications. Experimental results demonstrate detection of ppb (parts-per-billion) or ppt (parts-per-trillion) levels of hydrogen or mercury, respectively, for specially coated cantilevers. For bulk-like absorption, vapors do not stop at the gas\\/solid interface on the film but actually penetrate the

Zhiyu Hu

2000-01-01

282

Enhanced sensing performance of the amperometric gas sensor by laser-patterning of the polymer membrane electrode  

Microsoft Academic Search

Ultraviolet laser patterning has been employed for enhancing the sensing performance of the electrochemical gas sensors. Two kinds of catalyst layers (platinum for CO and gold for SO2) coated on the polytetrafluoloethylene film have been selectively removed by KrF laser irradiation. The laser fluence, repetition rate and number of shots were carefully controlled to avoid the damage of the membrane

Zongyi Qin; Pei-Nan Wang; Yujiang Wang

2005-01-01

283

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.

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

2010-01-01

284

Sensor validation and fusion for gas turbine vibration monitoring  

NASA Astrophysics Data System (ADS)

Vibration monitoring is an important practice throughout regular operation of gas turbine power systems and, even more so, during characterization tests. Vibration monitoring relies on accurate and reliable sensor readings. To obtain accurate readings, sensors are placed such that the signal is maximized. In the case of characterization tests, strain gauges are placed at the location of vibration modes on blades inside the gas turbine. Due to the prevailing harsh environment, these sensors have a limited life and decaying accuracy, both of which impair vibration assessment. At the same time bandwidth limitations may restrict data transmission, which in turn limits the number of sensors that can be used for assessment. Knowing the sensor status (normal or faulty), and more importantly, knowing the true vibration level of the system all the time is essential for successful gas turbine vibration monitoring. This paper investigates a dynamic sensor validation and system health reasoning scheme that addresses the issues outlined above by considering only the information required to reliably assess system health status. In particular, if abnormal system health is suspected or if the primary sensor is determined to be faulted, information from available "sibling" sensors is dynamically integrated. A confidence expresses the complex interactions of sensor health and system health, their reliabilities, conflicting information, and what the health assessment is. Effectiveness of the scheme in achieving accurate and reliable vibration evaluation is then demonstrated using a combination of simulated data and a small sample of a real-world application data where the vibration of compressor blades during a real time characterization test of a new gas turbine power system is monitored.

Yan, Weizhong; Goebel, Kai F.

2003-08-01

285

A study of surface modification at semiconducting Ga 2O 3 thin film sensors for enhancement of the sensitivity and selectivity  

Microsoft Academic Search

N-type semiconducting Ga2O3 thin films which are stable at high temperatures are being used as a new basic material for gas sensors. This study is an attempt to determine to what extent coating the surface of Ga2O3 thin films with another metal oxide will produce new gas sensitivities. The process involves sputtering a modification layer which is typically 30–300 nm

M. Fleischer; M. Seth; C.-D. Kohl; H. Meixner

1996-01-01

286

Vinegar Classification Based on Feature Extraction and Selection From Tin Oxide Gas Sensor Array Data  

Microsoft Academic Search

Tin oxide gas sensor array based devices were often cited in publications dealing with food products. However, during the process of using a tin oxide gas sensor array to analysis and identify different gas, the most important and difficult was how to get useful parameters from the sensors and how to optimize the parameters. Which can make the sensor array

Zou Xiaobo; Zhao Jiewen; Wu Shouyi; Huang Xingyi

2003-01-01

287

Factors influencing the gas sensing characteristics of tin dioxide films deposited by spray pyrolysis: understanding and possibilities of control  

Microsoft Academic Search

The main structure and electronic parameters of SnO2 thin films are considered from the point of view of optimization gas sensor characteristics. The results of phenomenological modeling and their comparison with experiments are used for choosing the correct film parameters and modes of deposition for the processing of SnO2 films by the spray pyrolysis method. Optimal deposition conditions were found,

V. Brinzari; G Korotcenkov; V Golovanov

2001-01-01

288

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 1000°C (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 1000°C (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 650°C) 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

289

Application of ZnO single-crystal wire grown by the thermal evaporation method as a chemical gas sensor for hydrogen sulfide.  

PubMed

A zinc oxide single-crystal wire was synthesized for application as a gas-sensing material for hydrogen sulfide, and its gas-sensing properties were investigated in this study. The gas sensor consisted of a ZnO thin film as the buffer layer and a ZnO single-crystal wire. The ZnO thin film was deposited over a patterning silicon substrate with a gold electrode by the CFR method. The ZnO single-crystal wire was synthesized over the ZnO thin film using zinc and activated carbon as the precursor for the thermal evaporation method at 800 degrees C. The electrical properties of the gas sensors that were prepared for the growth of ZnO single-crystal wire varied with the amount of zinc contained in the precursor. The charged current on the gas sensors increased with the increasing amount of zinc in the precursor. It was concluded that the charged current on the gas sensors was related to ZnO single-crystal wire growth on the silicon substrate area between the two electrodes. The charged current on the gas sensor was enhanced when the ZnO single-crystal wire was exposed to a H2S stream. The experimental results obtained in this study confirmed that a ZnO single-crystal wire can be used as a gas sensor for H2S. PMID:21446509

Park, N K; Lee, S Y; Lee, T J

2011-01-01

290

Niobium doped lead zirconate titanate films for infrared sensor application  

NASA Astrophysics Data System (ADS)

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

Han, Hui

291

Films of lutetium bisphthalocyanine nanowires as electrochemical sensors.  

PubMed

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

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

2010-11-17

292

Electronic characterization of thin diamondlike carbon films for pH sensor applications  

NASA Astrophysics Data System (ADS)

Amorphous Diamond like carbon (DLC) thin films were deposited on to 4'-silicon wafers by an electron cyclotron resonance microwave excited methan (CH4) or ethin (C2H2) plasma at low pressure. Electronic characterization of DLC films were performed by I/V and C/V measurements using MIS-structures. Whereas the electrochemical pH-characteristics were measured using ion- sensitive field-effect transistors. It is shown, that the type of carrier transport mechanism in DLC films depends on the process conditions and that the electrical conductivity varies over a wide range. This can be adjusted mainly by the kinetic energy of the CxHx+ ions and the C to H ratio, which depends on the type of process gas. The dominant charge transport mechanism in DLC films based on a methan plasma is the Poole-Frenkel emission whereas the charge flow for ethin based DLC films is space-charged limited. The electronic conductivity of DLC films deposited with ethin as process gas is typically about five orders of magnitude higher than methan based films. The electrochemical characterization shows a pH-sensitivity in the range of 50 - 57 mV/pH and a long-term pH signal stability in the range of 0.3 - 25 (mu) V/h. Based on the different pH-sensitivities int will be possible to produce a pH-sensor in differential mode using DLC/DLC or DLC/Ta2O5 combinations for the sensitive layers.

Schitthelm, Frank; Roever, Kai-Sven; Ferretti, Ruediger

1998-12-01

293

Absorption and desorption characteristic of zeolites in gas sensor system  

Microsoft Academic Search

Nanosized zeolites as a novel absorbent were investigated targeting for the nerve agent sarin stimulant gas DMMP. Quartz crystal microbalance (QCM) gas sensors modified with Silicalite-1 or Cu-ZSM-5 zeolites synthesized as micro-porous absorbents were fabricated and their gas response characteristics were examined to study the absorption capability of zeolites. The results indicated that Cu-ZSM-5 zeolite has stronger absorption capacity than

Wei Yao; Yuanyuan Hu; Xinming Ji; Nan Ren; Jia Zhou; Yiping Huang; Yi Tang

2008-01-01

294

Gas-film coefficients for streams  

USGS Publications Warehouse

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

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

1983-01-01

295

Investigation of MoO3-WO3 thin film microstructure for gas sensing applications  

NASA Astrophysics Data System (ADS)

MoO3-WO3 thin films have been fabricated via the sol-gel method. FESEM, TEM, RBS and SIMS analysis techniques have been employed to analyse the films and material properties for use as gas sensors to detect CO and NO2. FESEM shows the film made up of segregated molybdenum crystals. TEM highlights the nano-sized grains sructure and crystallinity. RBS analysis confirmed the films are stoichimetric and that the Mo component of the system decreases as the annealing temperature is increased. SIMS illustrates the interesting elemental depth profiles of the films. The films were exposed to CO and NO2. MoO3-WO3 shows better NO2 sensitivity and selectivity compared to its single metal oxide constituents.

Galatsis, Kosmas; Ghantasala, Muralidhar K.; Li, Yongxiang; Kalantar-Zadeh, Kourosh; Trinchi, Adrian; Wlodarski, Wojtek; Taurino, A.; Siciliano, Pietro; Cukrov, Lara

2001-11-01

296

Optical-fiber copolymer-film electric-field sensor.  

PubMed

Characteristics of a fiber-optic sensor for the detection of external electric fields are presented. This device utilizes a single-mode fiber that is embedded in a poled vinylidene fluoride-tetrafluoroethylene copolymer film and incorporated as the sensor arm of a Mach-Zehnder interferometer. A low-frequency intrinsic sensitivity of (0.20 +/- 0.03) x 10(-12) m/V is measured which compares well with our projected theoretical static sensitivity. This sensitivity implies a minimum detectable field of 33 microAV/m for a 1.0-km length of activated fiber and a 10(-7)-rad phase-shift detection capability. PMID:18195914

Mermelstein, M D

1983-04-01

297

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

298

The exploitation of thin film coatings for fibre sensors for the application of chemical sensing  

NASA Astrophysics Data System (ADS)

We report on the use of thin film coatings, both single and multi-layered, deposited on the flat side of a lapped, D-shaped fibre to enhance the sensitivity of two kinds of surface plasmon resonance based optical fibre sensors. The first kind involves the use of a tilted Bragg grating inscribed within the fibre core, prior to fibre coating, while the second relies on a surface relief grating photoinscribed after the fibre has been coated. Some of the devices operate in air with high coupling efficiency in excess of 40dB and an estimated index sensitivity of ??/?n = 90nm from 1 to 1.15 index range showing potential for gas sensing. Other sensors produced index sensitivities (??/?n) ranging from 6790nm to 12500nm in the aqueous index regime. The materials used for these fibre optical devices are germanium, silica, silver, gold and palladium.

Allsop, T.; Neal, R.; Kalli, K.; Davies, E. M.; Rehman, S.; Maier, R. R. J.; Barton, J.; Jones, J. D.; Webb, D. J.; Bennion, I.

2009-05-01

299

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

300

Hafnium Oxide Film Etching Using Hydrogen Chloride Gas  

Microsoft Academic Search

Hydrogen chloride gas removes the hafnium oxide film formed by atomic layer deposition at the etch rate of about 1 nm\\/min. A 100 nm-thick hafnium oxide film was perfectly etched off at 1173 K for 60 min by 100% hydrogen chloride gas at 100 sccm. A weight decrease in the hafnium oxide film was observed at temperatures higher than ca.

Hitoshi Habuka; Masahiko Yamaji; Yoshitsugu Kobori; Sadayoshi Horii; Yasuo Kunii

2009-01-01

301

A novel carbon dioxide gas sensor based on solid bielectrolyte  

Microsoft Academic Search

A planar bielectrolyte type of CO2 gas sensor based on Nasicon and Na??-alumina solid electrolyte pellets with BaCO3–Na2CO3 (weight ratio 44:56) as the auxiliary phase was fabricated. The sensor had good response to CO2 over a wide range covering 6ppm to 100%. The Nasicon\\/Pt interface was sensitive to oxygen, while auxiliary phase applied at low temperature on the sodium rich

Ling Wang; R. V. Kumar

2003-01-01

302

Advances in SiC Field Effect Gas Sensors  

Microsoft Academic Search

\\u000a Constraints around environmental issues continue to increase in severity. This causes a demand for increasing control of emissions\\u000a and reduction of energy consumption in vehicles and in industry, which necessitates the development and production of faster\\u000a and more efficient sensors for on-line control. Gas sensors that can function in extreme environments have the potential to\\u000a provide this control. Those based

A. Lloyd Spetz; S. Savage

303

Gas sensor network for air-pollution monitoring  

Microsoft Academic Search

This paper describes the development of a gas sensor system to be used as a sensing node to form a dense real-time environmental monitoring network. Moreover, a new auto-calibration method is proposed to achieve the maintenance-free operation of the sensor network. The network connectivity can be used not only for data collection but also for the calibration and diagnosis of

Wataru Tsujita; Akihito Yoshino; Hiroshi Ishida; Toyosaka Moriizumi

2005-01-01

304

Comparative study on micromorphology and humidity sensitive properties of thin-film and thick-film humidity sensors based on semiconducting MnWO 4  

Microsoft Academic Search

Based on our experience of developing thick-film MnWO4 humidity sensors, a thin-film humidity sensor with nano-sized MnWO4 grains has been fabricated using the sol–gel technique. The thin-film sensor shows smaller humidity sensitivity than that compared to a thick-film sensor. However, it exhibits a fast response to humidity change and also has a very low temperature coefficient within the temperature range

Wenmin Qu; Wojtek Wlodarski; Jörg-Uwe Meyer

2000-01-01

305

Thin film stress studies using microcantilevers and microcantilever sensors  

NASA Astrophysics Data System (ADS)

Adsorption-induced and absorption-induced stresses on coated microcantilevers can produce bending, which can be related to gas or vapor concentration for sensing applications. Experimental results demonstrate detection of ppb (parts-per-billion) or ppt (parts-per-trillion) levels of hydrogen or mercury, respectively, for specially coated cantilevers. For bulk-like absorption, vapors do not stop at the gas/solid interface on the film but actually penetrate the entire thickness of the film. An example is hydrogen adsorption in palladium that induces a volume expansion of the palladium film. The sensitivity of coated cantilevers is adjustable in a certain range by controlling the coating layer thickness. For surface-like adsorption, both stress and resistance changes depend only on the number of adsorbate atoms adsorbed onto the adsorbent surface. Film thickness has little effect on the sensitivity of coated cantilevers. An example is mercury adsorption onto a gold surface that causes a stress decrease. Novel simultaneous cantilever bending and electrical resistance measurements indicate that adsorption onto or absorption into thin metal films can induce stress changes and resistance changes at different rates. These differences may or may not vary with gas or vapor concentration depending on the interaction mechanisms; and they imply more complex chemical reactions during the adsorption process than were known before this study. Additional investigations will be required to ascertain such details. Effects of environmental influences, such as relative humidity and temperature, were also investigated. The investigation of mercury adsorption-induced stress on thin gold film undertaken here is believed to be the first complete work in this area. A surface adsorption model is proposed and shows excellent agreement with experimental data as well as that reported outside this dissertation. This model may serve as a guide for future studies in surface adsorption.

Hu, Zhiyu

306

New potentiomentric dissolved oxygen sensors in thick film technology  

Microsoft Academic Search

New designed dissolved oxygen potentiometric sensors in thick film technology based in the use of RuO2 as active material and TiO2 or polyisoftalamide diphenylsulphone (PIDS) as membranes have been developed. TiO2-coated RuO2 electrodes showed a linear response as a function of the logarithm of the dissolved oxygen concentration in the 0.5–8ppm range (log[O2], ?4.82 to ?3.60; concentration of O2 in

Ramón Mart??nez-Máñez; Juan Soto; Josefa Lizondo-Sabater; Eduardo Garc??a-Breijo; Luis Gil; Javier Ibáñez; Isabel Alcaina; Silvia Alvarez

2004-01-01

307

Semiconductor film bolometer technology for uncooled IR sensors  

NASA Astrophysics Data System (ADS)

This paper presents an overview of the research program on uncooled IR sensitive bolometer technology at the Defence Science and Technology Organisation (DSTO). It covers the design, materials growth, and performance of semiconductor film bolometer (SFB) IR detectors, with a strong emphasis on the practical considerations involved in their production. The overview includes a discussion of thermal isolation and the effects that vacuum packaging, and other alternative technologies, have on the performance of the detectors. Some of the principal applications of uncooled SFB IR detectors are also discussed. Finally, current technological developments in the DSTO uncooled sensor program and the direction of future research are described.

Unewisse, Mark H.; Liddiard, Kevin C.; Craig, Brian I.; Passmore, Stephen J.; Watson, Rodney J.; Clarke, Robert E.; Reinhold, Olaf

1995-09-01

308

Highly sensitive gas sensor based on integrated titania nanosponge arrays  

NASA Astrophysics Data System (ADS)

Highly sensitive gas sensors were fabricated using nanostructured titania pad arrays. Nanostructured titania (NST) formed is sponge-like consisting of interconnected nanoscale wires and walls, which are made up of anatase nanocrystals. Electrical characterization indicates that contacts were ohmic and NST was highly sensitive to O2. Variations of hundreds of oxygen molecules over a 20 ?m NST square pad sensing element were detected at 250 °C. The NST-based sensor operates at lower temperatures, has fast response time, and superior sensitivity relative to oxygen sensors based on porous undoped titania reported in the literature.

Zuruzi, A. S.; Kolmakov, A.; MacDonald, N. C.; Moskovits, M.

2006-03-01

309

Surface-mounted sensors for gas turbine research and development  

NASA Astrophysics Data System (ADS)

In the development of gas turbine aeroengines, the high cost of development testing and market lead pressure to reduce program timescales has led to increasing use of advanced instrumentation. A growing interest has been the integration of sensors into the engine components, both to look outward at the behavior of the flow over the component, and to look inward at the temperature and strain of the component itself. This paper describes a range of pieso-resistive and thermal sensor applications developed by Rolls-Royce concluding with a view of this industry's future needs and sensor design challenges.

Loftus, Peter; Shepherd, Richard; Stringfellow, Keith

1993-07-01

310

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

311

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

312

Battery charging system utilizing optical gas sensor  

Microsoft Academic Search

A battery charging system utilizing a gas pressure transducer which increases in resistance in response to increased gas pressure. The gas pressure transducer comprises an optical transducer. Respective rubber diaphragm chambers, communicating with the cells through glass and plastic tubing, are disposed to form a channel therebetween. A light bulb and a photo-resistor are placed at the respective ends of

Iseard

1984-01-01

313

Polymer flip-chip bonding of pressure sensors on a flexible Kapton film for neonatal catheters  

NASA Astrophysics Data System (ADS)

In this paper, we describe the development of a new approach to mounting silicon pressure microsensors inside a 5 French (1.67 mm outer diameter) neonatal catheter tube for intravascular blood pressure measurements. Kapton film was used as a low-cost, flexible interface between the flip-chip bonded sensors at one end and wires to external electronics at the other end. Conductive polymer paste was used to flip-chip bond sensors to the flexible Kapton substrate at low temperature, while gold traces were used to form electrical interconnects on the film surface. Conductivity and bonding strength of the resulting polymer bumps were on the order of 100 m? and 4.43 mN mm-2, respectively. Piezoresistive pressure microsensors were successfully mounted on Kapton carriers, packaged inside catheter tubes, and characterized in both gas and liquid environments. The sensors exhibited sensitivity of approximately 60 µV mmHg-1 over the target pressure range of 0-350 mmHg. Two-week tests in water at 27 °C and 36 °C showed only slight variations in contact resistances, indicating that the developed approach to packaging microsensors was sufficiently robust for the target application.

Li, Chunyan; Sauser, Frank E.; Azizkhan, Richard G.; Ahn, Chong H.; Papautsky, Ian

2005-09-01

314

Pattern Recognition for Selective Odor Detection with Gas Sensor Arrays  

PubMed Central

This paper presents a new pattern recognition approach for enhancing the selectivity of gas sensor arrays for clustering intelligent odor detection. The aim of this approach was to accurately classify an odor using pattern recognition in order to enhance the selectivity of gas sensor arrays. This was achieved using an odor monitoring system with a newly developed neural-genetic classification algorithm (NGCA). The system shows the enhancement in the sensitivity of the detected gas. Experiments showed that the proposed NGCA delivered better performance than the previous genetic algorithm (GA) and artificial neural networks (ANN) methods. We also used PCA for data visualization. Our proposed system can enhance the reproducibility, reliability, and selectivity of odor sensor output, so it is expected to be applicable to diverse environmental problems including air pollution, and monitor the air quality of clean-air required buildings such as a kindergartens and hospitals.

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

2012-01-01

315

Gas cell based on cascaded GRIN lens for optical fiber gas sensor  

NASA Astrophysics Data System (ADS)

Based on the theory of gas molecular absorption spectrum, a transmission type gas cell based on cascaded GRIN lens has been designed. The gas cell is the kernel of the optical fiber gas sensor system. The system performance is relative to rationality of gas cell structure. By using GRIN lens couple in gas cell, we can solve the problems of optical discrete components. We use GRIN lens with pigtail fiber as collimating or focusing lens for transmission type of gas cell. To shorten sensor's size and length, and enhance sensor's sensitivity, we present a method by using cascaded GRIN Lens couples to compose a gas cell. With this method, the optical path length is increased and the detection sensitivity of the gas cell is greatly increased. This transmission type of gas cell based on cascaded GRIN lens couples have been applied to our system of absorption spectrum optical fiber gas sensors. We designed and manufactured a gas cell with cascaded GRIN lens couples. Experimental results show that transmission gas cell based on cascaded GRIN lens couples has a good detecting effect.

Sa, Jiming; Chen, Youping; Zhang, Gang; Zhou, Zude; Cui, Lujun

2007-11-01

316

Structure and Absorbability of a Nanometer Nonmetallic Polymer Thin Film Coating on Quartz Used in Piezoelectric Sensors  

NASA Astrophysics Data System (ADS)

We present a new type of gas piezoelectric sensor taking quartz piezoelectric crystal as the basal material and nanometer nonmetallic polymer thin film coating as the surface. The coating, plated by vacuum electron beam dispersion (EBD) coating technology, is carried out by employing a nanometer nonmetallic polymer thin film that has properties of selecting and identifying characteristic materials. An experimental survey shows that EBD coating technology can produce a uniform thickness of the thin film coating, and the physical and chemical analyses show that the coating has a high performance of absorption using the method of infrared spectroscopy. Meanwhile, the absorption and sensitivity performance of the thin film coating will change if other organic materials are added to the coated thin film. Through the measurement of the thin film coating, the feature of sensitivity to the change of humidity is acquired. Based on the above description, a new type of gas piezoelectric sensor is designed and manufactured reasonably, which provides a valid method to rapidly monitor and distinguish complex gases.

Gu, Yu; Li, Qiang; Tian, Fang-Fang; Xu, Bao-Jun

2013-10-01

317

Structure of Palladium Nanoclusters for Hydrogen Gas Sensors  

SciTech Connect

Palladium nanoclusters produced by inert gas aggregation/magnetron sputtering are used as building blocks for the construction of nano electronic devices with large surface to volume ratios that can be used as sensitive hydrogen gas sensors in fuel cells and in petrochemical plants. X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and high resolution transmission electron microscopy (HRTEM) have been used to characterize the structure, lattice constant, particle diameter and oxide thickness of the palladium nanoclusters in order to understand the operation of these sensors. Grazing incidence XRD (GIXRD) of heat treated Pd clusters has shown that the palladanite structure forms at elevated temperatures.

Stevens, K.J.; Ingham, B.; Toney, M.F.; Brown, S.A.; Lassesson, A.; /SLAC, SSRL /Canterbury U.

2009-05-11

318

Measuring muscle movements for human interfaces using a flexible piezoelectric thin film sensor  

Microsoft Academic Search

This paper proposes a novel method to measure muscle movements for human interfaces. During muscle movements, cross-sectional muscle area changes, and this can be detected at the skin surface. In this study, a flexible piezoelectric thin film sensor is used to measure the morphological change of the skin surface. This sensor is made of oriented aluminum nitride (AlN) thin film,

Nan Bu; Junpei Tsukamoto; Naohiro Ueno; Keisuke Shima; Toshio Tsuji

2008-01-01

319

Low-cost portable respiration monitor based on micro hot-film flow sensor  

Microsoft Academic Search

We present a portable, low cost, sensitive respiration monitoring system based on a micro hot-film flow sensor. The sensitive component of the flow sensor is a patterned thin-film with nanometer thickness fabricated on a flexible polyimide substrate by incorporating printed circuit technique with micromachining technique. The respiratory flow measurement is under a constanttemperature mode, and the measured signals are sampled

Zhe Cao; Rong Zhu; Ruiyi Que

2010-01-01

320

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

321

Comparison among performance of strain sensors based on different semiconductor thin films  

NASA Astrophysics Data System (ADS)

In recent years, the piezoresistive properties of different semiconductor thin films, with chemical and mechanical stability, have been studied in order to use them as base material in the fabrication of strain sensors for high temperature applications. In this context, this work compares the performance of strain sensors based on sputter-deposited semiconductor thin films such as titanium dioxide (TiO2), silicon carbide (SiC) and diamond-like carbon (DLC) operated at temperatures up to 250°C. The structure of each sensor consists of four thin-film resistors, configured in Wheatstone bridge, with Ti/Au electrical contacts. These strain sensors reported here differ from our previous works in the types of materials used and in the quantity/configuration of the thin-film resistors. The strain sensors were fabricated by photolithography techiques in conjunction with lift-off processes. The beam-bending experiments were performed to characterize the sensors.

Fraga, Mariana A.; Furlan, Humber; Pessoa, Rodrigo S.

2011-05-01

322

Thick-film acoustic emission sensors for use in structurally integrated condition-monitoring applications.  

PubMed

Monitoring the condition of complex engineering structures is an important aspect of modern engineering, eliminating unnecessary work and enabling planned maintenance, preventing failure. Acoustic emissions (AE) testing is one method of implementing continuous nondestructive structural health monitoring. A novel thick-film (17.6 ?m) AE sensor is presented. Lead zirconate titanate thick films were fabricated using a powder/sol composite ink deposition technique and mechanically patterned to form a discrete thick-film piezoelectric AE sensor. The thick-film sensor was benchmarked against a commercial AE device and was found to exhibit comparable responses to simulated acoustic emissions. PMID:21937337

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

2011-09-01

323

Gas Sensors Characterization and Multilayer Perceptron (MLP) Hardware Implementation for Gas Identification Using a Field Programmable Gate Array (FPGA)  

PubMed Central

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

Benrekia, Faycal; Attari, Mokhtar; Bouhedda, Mounir

2013-01-01

324

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, Fayçal; Attari, Mokhtar; Bouhedda, Mounir

2013-03-01

325

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

Microsoft Academic Search

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

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

2009-01-01

326

Battery charging system utilizing optical gas sensor  

SciTech Connect

A battery charging system utilizing a gas pressure transducer which increases in resistance in response to increased gas pressure. The gas pressure transducer comprises an optical transducer. Respective rubber diaphragm chambers, communicating with the cells through glass and plastic tubing, are disposed to form a channel therebetween. A light bulb and a photo-resistor are placed at the respective ends of the channel. Increased gas pressure from the cells forces the centers of the diaphragm closer together to restrict the channel region, and thus decrease the light received by the photo-resistor as a function of gas pressure. In addition, a timing circuit utilizing the transistor for control of an SCR switch is disclosed.

Iseard, B.S.

1984-08-14

327

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

328

Gas-leak localization using distributed ultrasonic sensors  

Microsoft Academic Search

We propose an ultrasonic gas leak localization system based on a distributed network of sensors. The system deploys highly sensitive miniature Micro-Electro-Mechanical Systems (MEMS) microphones and uses a suite of energy-decay (ED) and time-delay of arrival (TDOA) algorithms for localizing a source of a gas leak. Statistical tools such as the maximum likelihood (ML) and the least squares (LS) estimators

Javid Huseynov; Shankar Baliga; Michael Dillencourt; Lubomir Bic; Nader Bagherzadeh

2009-01-01

329

A wireless, passive carbon nanotube-based gas sensor  

Microsoft Academic Search

A gas sensor, comprised of a gas-responsive multiwall carbon nanotube (MWNT)-silicon dioxide (SiO2) composite layer deposited on a planar inductor-capacitor resonant circuit is presented here for the monitoring of carbon dioxide (CO2), oxygen (O 2), and ammonia (NH3). The absorption of different gases in the MWNT-SiO2 layer changes the permittivity and conductivity of the material and consequently alters the resonant

Keat Ghee Ong; Kefeng Zeng; Craig A. Grimes

2002-01-01

330

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 11.6–21.7%. 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.

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

2012-01-01

331

Design of micro-sensor-array detector for toxic gas  

NASA Astrophysics Data System (ADS)

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

Liao, Hai-Yang; Tian, Peng

2010-08-01

332

Harmful Gas Recognition Exploiting a CTL Sensor Array.  

PubMed

In this paper, a novel cataluminescence (CTL)-based sensor array consisting of nine types of catalytic materials is developed for the recognition of several harmful gases, namely carbon monoxide, acetone, chloroform and toluene. First, the experimental setup is constructed by using sensing nanomaterials, a heating plate, a pneumatic pump, a gas flow meter, a digital temperature device, a camera and a BPCL Ultra Weak Chemiluminescence Analyzer. Then, unique CTL patterns for the four types of harmful gas are obtained from the sensor array. The harmful gases are successful recognized by the PCA method. The optimal conditions are also investigated. Finally, experimental results show high sensitivity, long-term stability and good linearity of the sensor array, which combined with simplicity, make our system a promising application in this field. PMID:24113681

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

2013-10-09

333

Glucose sensor based on organic thin film transistor using glucose oxidase and conducting polymer  

Microsoft Academic Search

An organic thin film transistor (OTFT)-based glucose sensor, with a channel consisting of glucose oxidase enzyme (GOx) immobilized with poly(3,4-ethylenedioxythiophene–poly(styrene-sulfonate) (PEDOT–PSS) conducting polymer film, has been investigated. GOx was immobilized on PEDOT–PSS conducting polymer film using a simple cost effective spin-coating technique, and was entrapped in the polymer matrix during electrochemical polymerization. Subsequently, the sensor was encapsulated within a cellulose

J. Liu; M. Agarwal; K. Varahramyan

2008-01-01

334

Thin-film magnetic sensor using high frequency magneto-impedance (HFMI) effect  

Microsoft Academic Search

This study reports on the performance of a thin-film magnetic sensor which uses the high frequency magneto-impedance (HFMI) effect. In order to obtain a high sensitivity and a large voltage change ratio (?Vpp\\/Vpp(0): corresponds to the MR ratio), a strip pattern, a closed magnetic circuit, and a NiFe\\/SIO2 multilayer film structure are adopted for the magnetic films of the sensor.

Masakatsu Senda; Osamu Ishii; Yasuhiro Koshimoto; Tomoyuki Toshima

1994-01-01

335

A High-Precision NDIR Gas Sensor for Automotive Applications  

Microsoft Academic Search

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

Robert Frodl; Thomas Tille

2006-01-01

336

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

337

Portable chemical gas sensor prototype for nitroaromatic compounds detection  

Microsoft Academic Search

This paper presents the conception and the development of portable gas sensor prototypes for nitroaromatic compounds detection. It is based on quartz crystal microbalance (QCM) principle and a data processing. The sensitive material is a polymer which was chosen for its good sensibility and robustness. This prototype is able to detect 3 ppm of nitroaromatic compound with a high selectivity.

F. Thery-Merland; P. Montmeat; E. Pasquinet; L. Hairault

2004-01-01

338

Vibrating capacitor method in the development of semiconductor gas sensors  

Microsoft Academic Search

Adsorption usually results in work function shifts on catalytically active surfaces such as semiconductor gas sensors. The purpose of the present article is to summarise the capabilities of the vibrating capacitor from the simplest adsorption-induced work function tests to the scanning, vibrating, capacitor-yielded olfactory pictures and other chemical pictures. After a brief history and review of theoretical bases, the latest

János Mizsei

2005-01-01

339

Study of Structural and Gas Sensing Properties of Tantalum Coated Polyaniline Composite Thin Films  

NASA Astrophysics Data System (ADS)

In the present work we have synthesized PANI by in-situ chemical oxidative polymerization method. The chemiresistor type gas sensors have been fabricated by deposited tantalum and polyaniline composite thin film on to interdigited electrodes (IDE) configuration using sputtering ad spin coating techniques respectively. The composite thin film was irradiated using 150 MeV Au+7 at the fluence of 1×1011 ions/cm2. The pristine Ta/PANI composite sensor showed negligible sensing response which was further improved up to 1.42 ((i.e. %Sensitivity ~30%) after SHI irradiation. The structural and morphological properties of composite sensing thin films have also been characterized by XRD and AFM measurement before and after SHI irradiation.

Srivastava, Subodh; Kumar, Sumit; Agrawal, Shweta; Sharma, S. S.; Kumar, Rajesh; Saxena, Arpita; Choudhary, B. L.; Mathur, Shubhra; Vijay, Y. K.

2011-07-01

340

Effect of microstructure on detection of dilute NO2 using WO3 thin film sensors  

Microsoft Academic Search

The effects of microstructure on NO2 sensing properties were investigated for WO3 thin film sensors fabricated on SiO2\\/Si substrate equipped with Au combtype microelectrodes. The effect of grain size for thin WO3 sensors was explained with the conventional model. On the other hand, the high sensitivity NO2 sensor was obtained due to unique thickness effect. For the sensors using WO3

Jun Tamaki; Atsushi Hayashi; Yoshifumi Yamamoto; Masao Matsuoka

2003-01-01

341

Final report for EMP instrumentation project DNA IACRO 75-815: magnetic thin film sensors  

Microsoft Academic Search

The magnetic thin film current sensor\\/recorder is a passive device which ; responds to the peak current and pulse shape of a transient event. The transient ; current information becomes a permanent record on the film. The thin film device ; is small, low mass and reusable. It has been proven to be fast (less than 1\\/2 ; nanosecond response),

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

1975-01-01

342

The design of a new integrated gas sensor array based on FEA  

Microsoft Academic Search

The temperature distribution of the integrated gas sensor array is discussed. Since it is difficult to measure the surface temperature on an integrated gas sensor chip experimentally, the finite element analysis (FEA) technique is used in our simulation design of the microstructure gas sensor array. First, the model is derived from the array's exact structure and physical features. Second, we

Wang Ping; Kong Liping; Wang Xiaoxiang; Li Jianping

2000-01-01

343

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

2005-01-13

344

Methods for gas detection using stationary hyperspectral imaging sensors  

SciTech Connect

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

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

2012-04-24

345

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

Microsoft Academic Search

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

M Penza; C Martucci; G Cassano

1998-01-01

346

Study on distributed optic fiber gas sensors  

Microsoft Academic Search

Online detection of gas concentrations is important research topic recently. Based on the analysis of near infrared spectral absorption of acetylene, ammonia and carbon monoxide, a system using absorption type optic fiber for high sensitivity distributed detection of gases with wideband light source is demonstrated. Light source modulation harmonic measurement is presented in this paper. Wavelength modulation is realized by

Jin Liu; Haima Yang; Yan Yue

2009-01-01

347

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

348

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

349

Portable electronic nose system with gas sensor array and artificial neural network  

Microsoft Academic Search

A portable electronic nose system has been fabricated and characterized using an oxide semiconductor gas sensor array and artificial neural network. The sensor array consists of such thick-film oxide semiconductor sensing materials as Pd-doped WO3, Pt-doped SnO2, TiO2–Sb2O5–Pd-doped SnO2, TiO2–Sb2O5–Pd-doped SnO2+Pd-coated layer, Al2O3-doped ZnO and PdCl2-doped SnO2. The portable electronic nose system consists of an Intel 80c196kc as CPU, an

Hyung-Ki Hong; Chul Han Kwon; Seung-Ryeol Kim; Dong Hyun Yun; Kyuchung Lee; Yung Kwon Sung

2000-01-01

350

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

351

Experimental Fabrication of High Efficiency Force Sensor by Cr-Si-C Composite Thin Film  

NASA Astrophysics Data System (ADS)

Chromium silicon carbide (Cr-Si-C) composite thin film has been deposited on the stainless steel substrate by radio frequency (RF) sputtering and the possibility of the force sensor is discussed. The characteristic of the Cr-Si-C composite thin film force sensor is also described. Small temperature coefficient of resistance (TCR) dispersion has been obtained by a Cr-Si-C composite thin film force sensor, and the TCR was between -20 and 10 ppm/°C at the aspect ratio of 510 and the film thickness of 15 nm. The force sensor with hysteresis-free and good linearity has been prepared on the stainless steel substrate by using the Cr-Si-C composite film. The gauge factor of force sensor has increased according to the reduction of film thickness and the increase of sensor pattern aspect ratio. The gauge factor reached 14.2 at the aspect ratio of 510 and the film thickness of 15 nm, which is 7 times larger than that of Ni-Cr strain gauge.

Kondo, Shinya; Tamaki, Hajime; Takenaka, Hiroshi; Takemura, Mamoru; Ogawa, Soichi

352

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

353

Response speed of SnO2-based H2S gas sensors with CuO nanoparticles  

Microsoft Academic Search

CuO nanoparticles on sputtered SnO2 thin-film surface exhibit a fast response speed (14 s) and recovery time (61 s) for trace level (20 ppm) H2S gas detection. The sensitivity of the sensor (S~2.06×103) is noted to be high at a low operating temperature of 130 °C. CuO nanoparticles on SnO2 allow effective removal of excess adsorbed oxygen from the uncovered

Arijit Chowdhuri; Vinay Gupta; K. Sreenivas; Rajeev Kumar; Subho Mozumdar; P. K. Patanjali

2004-01-01

354

Comparison of spectral transmittance degradation due to organic gas contamination with on-orbit degradations of launched sensors  

NASA Astrophysics Data System (ADS)

Gas adsorption onto optical surfaces installed on satellites is one of the causes of signal degradation that occurs in orbit. To estimate the transmittance degradation caused by gas adsorption, transmittance measurements were carried out within the wavelength range of 200 nm to 14 ?m. Five types of glasses, SiO2, BK7, Al2O3, CaF2 and ZnSe were selected as glass samples and three gas species were chosen as the adsorption gas samples: 2-propanol, ethyl acetate and dichloromethane. These three molecules are typical paint solvents. In the IR wavelength range, several absorption bands corresponding to vibration and/or bending transitions of the functional groups present in the adsorbed molecules were detected. In the UV-VIS wavelength range, there were no local absorption features; however, broad transmittance degradations were detected. The comparison of measured spectral transmittance degradations with sensor output degradations showed that the signal degradations of launched sensors were similar to the transmittance degradation due to 2-propanol or dichloromethane adsorption. Moreover, we estimated the growth rate of the adsorbed molecular film thickness using the degradation data of the orbiting sensor, MODIS/Aqua, under the assumption that the signal degradation was caused by organic gas adsorption. Our estimation showed that the growth rate of an adsorbed molecular film decreased with time after the launch.

Itoh, Nobunari; Katoh, Masahiro; Okano, Nobuaki

2008-11-01

355

Pseudorandom binary sequence interrogation technique for gas sensors  

Microsoft Academic Search

Electrically conducting organic polymers are widely used as a means of gas, odour or aroma analysis using multi-element array techniques coupled with direct current (d.c.) interrogation techniques. Recently, it has been established that the use of alternating current (a.c.) interrogation gives rise to improved performance. In addition, the need to use multi-element arrays is much reduced since a single sensor

M. E. H Amrani; R. M Dowdeswell; P. A Payne; K. C Persaud

1998-01-01

356

Gas sensor using high-frequency quartz crystal microbalance  

Microsoft Academic Search

Fundamental modes (9 & 50 MHz) and overtone modes of 3rd mode of 33 MHz (100(3) MHz) and 5th mode of 20 MHz (100(5) MHz) of quartz crystal microbalances. (QCMs) with high frequencies are studied to increase the frequency response of QCM gas-sensor. On the fundamental and overtone modes, the ratio of mass sensitivity of QCMs calculated from theory is

Shigeru Kurosawa; Dae-Sang Han; Jong-Won Park; Hidenobu Aizawa; Minoru Yoshimoto; Chikashi Nakamura; J. Miyake; Sang-Mok Chang

2001-01-01

357

Hydrogen gas sensor based on highly ordered polyaniline nanofibers  

Microsoft Academic Search

Presented is the structural and gas sensing properties of polyaniline nanofibers deposited on 36° lithium tantalate (LiTaO3) surface acoustic wave (SAW) transducers. The polyaniline nanofibers were synthesized using electropolymerization and subsequently dedoping technique. Field emission scanning electron microscopy (FE-SEM) revealed that the diameter of the polyaniline nanofibers is in the range of 40–50nm. The SAW sensors with different thicknesses of

R. Arsat; X. F. Yu; Y. X. Li; W. Wlodarski; K. Kalantar-zadeh

2009-01-01

358

Optical hydrogen sensor based on etched fiber Bragg grating sputtered with Pd/Ag composite film  

NASA Astrophysics Data System (ADS)

A novel fiber optical fiber hydrogen sensor based on etched fiber Bragg grating coated with Pd/Ag composite film is proposed in this paper. Pd/Ag composite films were deposited on the side-face of etched fiber Bragg grating (FBG) as sensing elements by magnetron sputtering process. The atomic ratio of the two metals in Pd/Ag composite film is controlled at Pd:Ag = 76:24. Compared to standard FBG coated with same hydrogen sensitive film, etched FBG can significantly increase the sensor's sensitivity. When hydrogen concentrations are 4% in volume percentage, the wavelength shifts of FBG-125 ?m, FBG-38 ?m and FBG-20.6 ?m are 8, 23 and 40 pm respectively. The experimental results show the sensor's hydrogen response is reversible, and the hydrogen sensor has great potential in hydrogen's measurement.

Dai, Jixiang; Yang, Minghong; Yu, Xun; Lu, Hong

2013-01-01

359

Application of the laser scanning confocal microscope in fluorescent film sensor research  

NASA Astrophysics Data System (ADS)

Confocal microscopy offers several advantages over conventional optical microscopy; we show an experimental investigation laser scanning confocal microscope as a tool to be used in cubic boron nitride (cBN) film-based fluorescent sensor research. Cubic boron nitride cBN film sensors are modified with dansyl chloride and rhodamine B isothiocyanate respectively. Fluorescent modification quality on the cubic boron nitride film is clearly express and the sensor ability to Hg2+ cations and pH are investigated in detail. We evidence the rhodamine B isothiocyanate modified quality on cBN surface is much better than that of dansyl chloride. And laser scanning confocal microscope has potential application lighttight fundus film fluorescent sensor research.

Zhang, Hongyan; Liu, Wei-Min; Zhao, Wen-Wen; Dai, Qing; Wang, Peng-Fei

2010-05-01

360

Mesoporous thin films of ``molecular squares'' as sensors for volatile organic compounds  

SciTech Connect

Mesoporous thin films of rhenium-based molecular squares, [Re(CO){sub 3}Cl(L)]{sub 4} (L = pyrazine, 4,4{prime}-bipyridine), have been utilized as sensors for volatile organic compounds (VOCs). The sensing was conducted using a quartz crystal microbalance with the target compounds present in the gas phase at concentrations ranging from 0.05 to 1 mM. Quartz crystal microbalance studies with these materials allowed for distinction between the following VOCs: (1) small aromatic versus aliphatic molecules of almost identical size and volatility and (2) an array of benzene molecules derivatized with electron donating/withdrawing substituents. The experiments suggest that the mesoporous host materials interact with VOC guest molecules through both van der Waals and weak charge-transfer interactions. In addition, size selectivity is shown by exposure of the molecular squares to cyclic ethers of differing size.

Keefe, M.H.; Slone, R.V.; Hupp, J.T.; Czaplewski, K.F.; Snurr, R.Q.; Stern, C.L.

2000-04-18

361

Fabrication of a miniaturized ionization gas sensor with polyimide spacer  

NASA Astrophysics Data System (ADS)

Gas sensing can be achieved by fingerprinting the ionization characteristics of distinct species. In this study, the fabrication of a miniaturized gas ionization sensor using polyimide as sacrificial layer is reported. The sensor consists of two planar metallic electrodes with a gap spacing obtained by the polyimide under-etching. This known sacrificial layer has the advantage besides a high planarization factor, to be CMOS compatible. Furthermore, its chemical resistance up to high temperatures, high resistance to radiation from both electrons and neutrons, and low outgassing are of primary importance to avoid interferences with the ionization gas sensing. A suspended micro-bridge with dimensions 20 ?m width and 220 ?m length has been developed and released by using etching holes in the membrane. The ionization characteristics of air at controlled temperature, humidity and pressure (21°C, 40% humidity and 1 atm) have been obtained during non-destructive electrical characterizations, with a breakdown voltage of 350 V for a 6 ?m gap. The growth of metallic nanowires templated in ion track-etched polyimide on the electrode is envisioned in order to enhance the ionization field and to reduce the required measurement power of the sensor.

Walewyns, T.; Scheen, G.; Tooten, E.; El Fissi, L.; Dupuis, P.; Francis, L. A.

2011-05-01

362

CMOS Alcohol Sensor Employing ZnO Nanowire Sensing Films  

NASA Astrophysics Data System (ADS)

This paper reports on the utilization of zinc oxide nanowires (ZnO NWs) on a silicon on insulator (SOI) CMOS micro-hotplate for use as an alcohol sensor. The device was designed in Cadence and fabricated in a 1.0 ?m SOI CMOS process at XFAB (Germany). The basic resistive gas sensor comprises of a metal micro-heater (made of aluminum) embedded in an ultra-thin membrane. Gold plated aluminum electrodes, formed of the top metal, are used for contacting with the sensing material. This design allows high operating temperatures with low power consumption. The membrane was formed by using deep reactive ion etching. ZnO NWs were grown on SOI CMOS substrates by a simple and low-cost hydrothermal method. A few nanometer of ZnO seed layer was first sputtered on the chips, using a metal mask, and then the chips were dipped in a zinc nitrate hexahydrate and hexamethylenetramine solution at 90° C to grow ZnO NWs. The chemical sensitivity of the on-chip NWs were studied in the presence of ethanol (C2H5OH) vapour (with 10% relative humidity) at two different temperatures: 200 and 250° C (the corresponding power consumptions are only 18 and 22 mW). The concentrations of ethanol vapour were varied from 175-1484 ppm (pers per million) and the maximum response was observed 40% (change in resistance in %) at 786 ppm at 250° C. These preliminary measurements showed that the on-chip deposited ZnO NWs could be a promising material for a CMOS based ethanol sensor.

Santra, S.; Ali, S. Z.; Guha, P. K.; Hiralal, P.; Unalan, H. E.; Dalal, S. H.; Covington, J. A.; Milne, W. I.; Gardner, J. W.; Udrea, F.

2009-05-01

363

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

Microsoft Academic Search

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

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

2002-01-01

364

Nickel-oxide film as an AR coating of Si window for IR sensor packaging  

NASA Astrophysics Data System (ADS)

An infrared (IR) transparent window is necessary for the IR sensor package. The most commonly used materials for IR transparent window are germanium (Ge) and silicon (Si). Ge has excellent optical properties but also the disadvantage of expensive price. Si has merits such as inexpensive cost and CMOS process compatibility but it has lower transmittance in the range of LWIR region than Ge. Therefore, an alternative anti-reflection (AR) coating is necessary to increase the transmittance of Si as an IR transparent window in the LWIR region. A simple single layer antireflection coating was newly designed on the silicon window for the infrared sensor package. Among the various materials, nickel oxide (NiO) was selected as an AR coating material due to its suitable optical properties and simple process. NiO film was deposited onto the double sided polished Si wafer by reactive rf sputtering with Ni target in an environment of Ar and O2 mixed gas. The thickness of the NiO film was determined by Essential Macleod simulation. FT-IR was used to measure the transmittance of the samples in the LWIR region. After the nickel oxide film was sputtered onto the double sides of the silicon wafer, the measured transmittance of the Si wafer was increased over 20% in the LWIR region compared with that of uncoated Si wafer. Additionally, annealing effect on the transmittance of NiO coated Si wafer was studied. By increasing the annealing temperature from 300° to 700°, an additional increase of transmittance was achieved.

Shim, Hyunbin; Kim, Dongsoo; Kang, Ingu; Kim, Jinkwan; Lee, Hee Chul

2013-06-01

365

Portable oral malodor analyzer using highly sensitive In 2O 3 gas sensor combined with a simple gas chromatography system  

Microsoft Academic Search

A portable oral malodor analyzer was developed for quantitative detection of volatile sulfur compounds (VSCs) in mouth air using a combination of a semiconductor gas sensor and a compact gas chromatography system. We found that In2O3 doped with Au is the optimum sensing material of the gas sensor for obtaining a high sensitivity to measure all the VSCs in mouth

Mariko Hanada; Hiroshi Koda; Kazuo Onaga; Katsuyuki Tanaka; Takahiro Okabayashi; Takeshi Itoh; Hideo Miyazaki

2003-01-01

366

Nanostructure-engineered chemical sensors for hazardous gas and vapor detection  

NASA Astrophysics Data System (ADS)

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

Li, Jing; Lu, Yijiang

2004-12-01

367

Tungsten trioxide-based thick-film NO sensor: design and investigation  

Microsoft Academic Search

New thick-film WO3 based sensors for the determination of NO levels in steam power plants emissions developed and manufactured at the Laboratory of Electronic Engineering Materials (PTI, Minsk) have been tested in NO, CO or CH4 containing environments. WO3(Bi2O3) thick films have been used as NO sensitive elements in the sensors. The same metal oxide composition has been successfully applied

A. A. Tomchenko; I. L. Emelianov; V. V. Khatko

1999-01-01

368

Dynamic gas sensor network for air pollution monitoring and its auto-calibration  

Microsoft Academic Search

The use of a dynamic gas sensor network is proposed for air pollution monitoring, and its auto-calibration is discussed to achieve the maintenance-free operation. Although the gas sensor outputs generally show drift over time, frequent recalibration of a number of sensors in the network is a laborious task. To solve this problem, instead of the static network proposed in the

Wataru Tsujita; Hiroshi Ishida; Toyosaka Moriizumi

2004-01-01

369

Polymer coated quartz crystal microbalance sensors for detection of volatile organic compounds in gas mixtures  

Microsoft Academic Search

By coating different conducting polymers of thiophene and its derivatives on quartz crystal microbalance (QCM) sensor surfaces, new novel QCM gas sensors have been produced in two simple ways, which could classify testing gas samples of volatile organic compounds (VOCs) gases. Principle components analysis (PCA) has been performed based on the QCM measurement results, which shows that our QCM sensors

Pengchao Si; John Mortensen; Alexei Komolov; Jens Denborg; Preben Juul Møller

2007-01-01

370

Combining inorganic and organic gas sensors elements: a new approach for multi-component sensing  

Microsoft Academic Search

Atmospheric dependent, gas sensitive resistors seem to be good candidates for detecting critical air pollution levels. Recently, great progress has been made in the development of various sensor types, but less attention seems to be paid to the integration of sensor elements with different characteristics. The aim of this international project is to develop a smart hybrid gas multi-sensor module

G. Harsányi; M. Réczey; R. Dobay; I. Lepsényi; Zs. Illyefalvi-Vitéz; J. Van den Steen; A. Vervaet; W. Reinert; J. Urbancik; A. Guljajev; Cs. Visy; Gy. Inzelt; I. Bársony

1999-01-01

371

Thin-Film Air-Mass-Flow Sensor of Improved Design Developed.  

National Technical Information Service (NTIS)

Researchers at the NASA Glenn Research Center have developed a new air-mass-flow sensor to solve the problems of existing mass flow sensor designs. NASA's design consists of thin-film resistors in a Wheatstone bridge arrangement. The resistors are fabrica...

G. C. Fralick J. D. Wrbanek D. P. Hwang

2003-01-01

372

Quartz crystal microbalance coated with carbon nanotube films used as humidity sensor  

Microsoft Academic Search

The possibilities and properties of multi-wall carbon nanotube (MWNT)-coated quartz crystal microbalance (QCM) as a humidity sensor are presented. In order to enhance effectively sensitivity of the sensor, the MWNTs coated on QCM are treated by means of ball milling and hydrogen plasma technique, respectively. The morphology and microstructure of MWNT films were characterized with SEM and TEM. It can

Yongsheng Zhang; Ke Yu; Rongli Xu; Desheng Jiang; Laiqiang Luo; Ziqiang Zhu

2005-01-01

373

Optimal Thermal Design of Micro Hot-film Wall Shear Stress Sensor  

Microsoft Academic Search

A series of numerical analyses of the unsteady conjugate heat transfer around a micro hot-film sensor are made in order to improve its response in the wall shear stress measurement. It is found that the frequency response of an ideal sensor is limited even in the absence of the heat conduction loss to the substrate. Heat conduction in the fluid

Takashi YOSHINO; Yuji SUZUKI; Nobuhide KASAGI; Shoji KAMIUNTEN

374

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

Microsoft Academic Search

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

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

1976-01-01

375

Method for measuring thickness of dielectric films using microdielectric fringe-effect sensors.  

PubMed

A method for noninvasive thickness measurements of dielectric films using fringe-effect (FE) sensors is developed and experimentally validated. The fringing electrical field, created by electrodes microfabricated at the film substrate, depends on the film thickness and dielectric permittivity of the film under test (FUT). The unknown film thickness is estimated by matching the theoretical prediction of thickness-dependent sensor admittance with the measured value. In the case of FE sensors with spatially periodic, interdigitated electrode (IDE) configuration, the admittance prediction is simplified, which allows for the real-time measurements of changing thickness. The developed method can be used to continuously measure the changing dielectric permittivity of the FUT material, which makes it possible to determine the thickness of films of changing dielectric properties, caused by chemical or other transformations. The application of the developed method is demonstrated experimentally by measuring the thickness of silicon nitride film deposited in several increments on the quartz substrate of the IDE sensor. In the expected range of sensor sensitivity, the results show an excellent agreement with the independent thickness measurements. PMID:16689522

Choi, Yunn-Hong; Tathireddy, Prashant; Skliar, Mikhail

2006-05-15

376

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

377

Contribution of polymeric swelling to the overall response of capacitive gas sensors.  

PubMed

A new method for investigation of the swelling of polymers on exposure to gas or vapour has been devised and tested. It uses an optical profilometer (based on the chromatic aberration of a lens system) which is integrated into a computer-controlled gas-dosing and mixing setup. Gas and/or vapour concentration-dependent measurements have been carried out for thick layers of the polymers commonly used in gravimetric and capacitive gas sensors: poly(acrylic acid) (PAA), poly(vinyl pyrrolidone) (PVP), poly(ether urethane) (PEUT), and polydimethylsiloxane (PDMS). The thickness of PAA, PVP, and PEUT films changed significantly on exposure to humidity. These data have been used to derive the sorption isotherms of the respective polymers, which were found to be Henry or Flory-Huggins isotherms. Comparison of the geometrical (swelling) responses with capacitive responses revealed a strong correlation. The correlation, which occurs because both types of response are proportional to the water content of the polymer, is also valid for polymers with nonlinear gas responses. Finally the geometrical and electrical characteristics of the capacitive samples were used to explain the dependence of the capacitive response of different polymers on the concentration of the target gas or vapour. In this way was deduced that PDMS, which does not swell on exposure to humidity, swells in the presence of 2,3-dimethylpentane, for which no profilometer evaluations are yet available. PMID:23685905

Altenberend, U; Oprea, A; Barsan, N; Weimar, U

2013-05-18

378

Microfabricated Thin Film Impedance Sensor & AC Impedance Measurements  

PubMed Central

Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were carried out. Testing media include 0.001 M, 0.01 M, 0.1 M NaCl and KCl solutions, and alumina (?3 ?m) and sand (?300 ?m) particulate layers saturated with NaCl solutions with the thicknesses ranging from 0.6 mm to 8 mm in a testing cell, and the results were used to assess the effect of the thickness of the particulate layer on the conductivity of the testing solution. The calculated resistances were approximately around 20 M?, 4 M?, and 0.5 M? for 0.001 M, 0.01 M, and 0.1 M NaCl solutions, respectively. The presence of the sand particulates increased the impedance dramatically (6 times and 3 times for 0.001 M and 0.1 M NaCl solutions, respectively). A cell constant methodology was also developed to assess the measurement of the bulk conductivity of the electrolyte solution. The cell constant ranged from 1.2 to 0.8 and it decreased with the increase of the solution thickness.

Yu, Jinsong; Liu, Chung-Chiun

2010-01-01

379

Temperature-dependent fiber optic hydrogen gas sensor response characteristics  

Microsoft Academic Search

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%N2 mixing gas concentration. The fiber cladding modified grating, without cladding chemical etching process, demonstrates 540 pm per 1% H2 sensitivity, a better

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

2006-01-01

380

Effects of marine biofouling on gas sensor membrane materials.  

PubMed

The use of underwater gaseous sensors has increased rapidly in the last 10 years. The majority of such sensors employ a thin membrane through which the gas diffuses. These sensors are potentiometric gas-sensing probes and essentially they are ion-selective electrodes. The deployment time of these membranes is curtailed by the formation of biofouling on the membrane leading to erroneous results. The physical properties of a variety of commonly used membranes were investigated using SEM and AFM. This showed that there were differences in topography between the PTFE membranes, such as pore sizes and surface roughness, which may be attributed to the manner in which they are manufactured. The pore size of the PTFE membranes varied greatly, ranging from circular pores with a diameter of 500 nm to elongated pores measuring 1 x 22 microm. The contact angle of each membrane showed that they were all hydrophobic. The amount of fouling on each was also observed and its affect on oxygen diffusion was monitored. Fouling slowed down the response of the instrument and caused reduced diffusion through the membranes. The amount of fouling varied between the membranes with the YSI membrane fouling least. Some of the membranes tested did foul less than others and there could be lifetime advantages of choosing a membrane with a smoother surface and a small pore size. PMID:18049777

Smith, M J; Kerr, A; Cowling, M J

2007-10-09

381

An ammonia gas sensor with two chambers based on U-bending microring resonator  

NASA Astrophysics Data System (ADS)

A compact ammonia gas sensor with two gas chambers is proposed in this paper, whose core sensing device is a U-bending microring resonator. The waveguides of ring part and feedback part in this resonator are made of silicon on insulator (SOI) ridge waveguide covered with ZnO nanocrystals which are sensitive to ammonia gas. The sensor can measure two groups of gas samples simultaneously. By computer simulation, we obtain the clear sensitivity curves of two gas chambers in ammonia sensor when the gas concentration increases from 0 to 4‰. The gas concentrations in two chambers can be obtained from one output spectrum, which significantly reduces the material and time consumption.

Zhang, Xin; Li, Zhi-quan; Sun, Yu-chao; Tong, Kai

2013-09-01

382

Adaptive radial artery pulse rate measurement using Piezo film sensor based on ensemble empirical mode decomposition  

Microsoft Academic Search

This research aims to measure the radial artery pulse rate using Piezo film sensor. Being thin and lightweight, Piezo film can be particularly useful for wearable applications. However, it suffers from different kinds of noises. We use EEMD analyzing method to estimate the radial pulse from the noisy data. Although EEMD is considered to be an adaptive method, it is

Mohamed Kharrat; Yuki Wakuda; Shinsuke Kobayashi; N. Koshizuka; K. Sakamura

2010-01-01

383

Low-Temperature Thick-Film Systems for Electronic and Sensor Applications  

Microsoft Academic Search

This paper presents recent work on complete thick-film systems, including dielectrics, conductors and resistors, with a lowered firing temperature range of 450…750°C. These materials allow the extension of proven, reliable and inexpensive thick-film technology to novel applications in electronics and sensors.

Thomas Maeder; Claudio Grimaldi; Sonia Vionnet; Caroline Jacq; Hansu Birol; Sigi Strässler; Peter Ryser

384

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, Frédéric; Guichard, Frédéric; Hornung, Hervé; Tessière, Régis

2012-01-01

385

Sol-gel processed MoO3 and WO3 thin films for use as selective chemo-sensors  

NASA Astrophysics Data System (ADS)

Selective detection of small amounts of toxic gases, such as ammonia and CO is very important to environmental monitoring as well as for medical diagnoses. MoO3 and WO3 have been identified as suitable materials for detecting these gases with high sensitivity. Sol-gel processed thin films of MoO3, WO3 and their combination have been prepared at SUNY Stony Brook by the hydrolysis of metal alkoxide precursors followed by spin coating and were deposited on alumina heater/electrode containing substrates that were produced by the Brescia group. Sensing tests were carried out in the state-of-the-art gas sensor testing facilities available in Brescia, where the electrical resistance of sensor arrays was recorded as a function of gas concentration, for various combinations of gases (including ammonia, CO, NO2, Methanol, isoprene, etc) at 10% relative humidity and at temperatures ranging from 400-500°C. The MoO3-WO3 composite system showed the best stability at the highest testing temperature. The sensing results obtained are correlated with the structural characteristics of the sensing films. This work has been carried out as a joint collaboration between the Advanced Materials Characterization Laboratory of SUNY Stony Brook (USA) and the Sensor Lab at the University of Brescia (Italy) and was funded by a NSF-AAAS (WISC) grant awarded to Perena Gouma.

Gouma, Perena; Comini, Elisabetta; Sberveglieri, Giorgio

2004-03-01

386

Fiber optic Bragg grating sensors for hydrogen gas sensing  

NASA Astrophysics Data System (ADS)

We report a new type of optical hydrogen sensor with a fiber optic Bragg grating (FBG) coated with palladium. The sensing mechanism in this device is based on the mechanical stress that is induced in the palladium coating when it absorbs hydrogen. The stress in the palladium coating stretches and shifts the Bragg wavelength of the FBG. Using FBGs with different wavelengths many such hydrogen sensor can be multiplexed on a single optical fiber. Operation of two multiplexing sensors is demonstrated. Moreover, hydrogen and thermal sensitivities of the senors were measured and calculated using a simple elastic model. Moreover, to quantify the amount of stress in the palladium film as a function of hydrogen concentration, a novel and very sensitive method was devised and used to detect deflections in a Pd-coated cantilever using an evanescent microwave probe. This stress was in the range of 5.26 - 8.59 X 107 Pa for H2 concentrations of 0.5 - 1.4% at room temperature, which is about three times larger than that found in the bulk palladium for the same range of H2 concentrations.

Sutapun, Boonsong; Tabib-Azar, Massood; Kazemi, Alex A.

1999-05-01

387

[A mobile sensor for remote detection of natural gas leakage].  

PubMed

The detection of natural gas pipeline leak becomes a significant issue for body security, environmental protection and security of state property. However, the leak detection is difficult, because of the pipeline's covering many areas, operating conditions and complicated environment. A mobile sensor for remote detection of natural gas leakage based on scanning wavelength differential absorption spectroscopy (SWDAS) is introduced. The improved soft threshold wavelet denoising was proposed by analyzing the characteristics of reflection spectrum. And the results showed that the signal to noise ratio (SNR) was increased three times. When light intensity is 530 nA, the minimum remote sensitivity will be 80 ppm x m. A widely used SWDAS can make quantitative remote sensing of natural gas leak and locate the leak source precisely in a faster, safer and more intelligent way. PMID:22512213

Zhang, Shuai; Liu, Wen-qing; Zhang, Yu-jun; Kan, Rui-feng; Ruan, Jun; Wang, Li-ming; Yu, Dian-qiang; Dong, Jin-ting; Han, Xiao-lei; Cui, Yi-ben; Liu, Jian-guo

2012-02-01

388

Side-polished fiber Bragg grating hydrogen sensor with different sensitive thin films  

NASA Astrophysics Data System (ADS)

WO3-Pd and Pd-Ag composite films were deposited on the side-face of side-polished fiber Bragg grating as sensing element by magnetron sputtering process. Compared to common FBG coated with same hydrogen sensitive film, side-polished FBG significantly increase the sensor's sensitivity. When the hydrogen concentration is 4% and 8% in volume percentage, the maximum wavelength shift of side-polished FBG is about 25 and 55 pm respectively. The experiment results show the sensor's hydrogen response is reversible, side-polished FBG hydrogen sensor has great potential in hydrogen's measurement.

Yang, Minghong; Dai, Jixiang; Cao, Kun; Liao, Junsheng; Zhang, Pengcheng

2012-01-01

389

Optical fiber sensors with Fabry-Perot thin film coating as sensitive element  

NASA Astrophysics Data System (ADS)

A fiber-optic relative-humidity sensor composed of two silver coating and a polymer film is proposed and developed. Ag coatings are magnetically sputtered, and sandwiched by a dip-coated moisture-sensitive polyvinyl alcohol (PVA) film, which constructs a low-fineness Fabry-Perot sensing head. Experimental results show that interference fringe shifts to longer wavelength when relative humidity increases. The interference fringe shifts of two-layer sensor and three-layer sensor are 5.3 nm and 1.9 nm respectively. The linearity of interference fringe shift to relative humidity is averagely 0.9874.

Yang, Minghong; Li, Xiaobing; Wang, Junjie; Tong, Xinglin

2010-05-01

390

A cubic boron nitride film-based fluorescent sensor for detecting Hg2+  

NASA Astrophysics Data System (ADS)

Cubic boron nitride (cBN) film-based sensors for detecting Hg2+ ions were developed by surface functionalization with dansyl chloride. To immobilize dansyl chloride, 3-aminopropyltriethoxy silane was modified on hydroxylated cBN surfaces to form an amino-group-terminated self-assembled monolayer. The covalent attachment of the amino groups was confirmed by x-ray photoelectron spectroscopy. The selectivity and sensitivity of the sensors to detect diverse metal cations in ethanol solutions were studied by using fluorescence spectroscopy, revealing a great selectivity to Hg2+ ions. Significantly, the dansyl-chloride-functionalized cBN film sensors were recyclable after the sensing test.

Liu, W. M.; Zhao, W. W.; Zhang, H. Y.; Wang, P. F.; Chong, Y. M.; Ye, Q.; Zou, Y. S.; Zhang, W. J.; Zapien, J. A.; Bello, I.; Lee, S. T.

2009-05-01

391

Design and fabrication of implantable wireless pressure and oxygen sensors based on PDMS thin films for application in pediatric surgery  

Microsoft Academic Search

In this paper, PDMS thin films were used in order to develop implantable, batteryless, telemetric integrated pressure and oxygen sensors, suitable for clinical cardiovascular applications in infants and children, in a novel capacitive and electrochemical sensor designs.

M. W. K. Nomani; Jie Liu; Moonbin Yim; Xuejun Wen; T.-Y. Hsia; G. Koley

2009-01-01

392

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

SciTech Connect

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

Hughes, R.C.; Moreno, D.J.; Jenkins, M.W.; Rodriguez, J.L.

1993-10-01

393

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

394

Superconducting Film Flux Transformer for a Sensor of a Weak Magnetic Field  

NASA Astrophysics Data System (ADS)

The object of study is a superconducting film flux transformer in the form of a square shaped loop with the tapering operative strip used in a sensor of a weak magnetic field. The magnetosensitive film element based on the giant magnetoresistance effect is overlapped with the tapering operative strip of the flux transformer; it is separated from the latter by the insulator film. It is shown that the topological nanostructuring of the operative strip of the flux transformer increases its gain factor by one or more orders of magnitude, i.e. increases its efficiency, which leads to a significant improvement of important parameters of a magnetic-field sensor.

Ichkitidze, L.; Mironyuk, A.

2012-12-01

395

Ionic liquid high-temperature gas sensor array.  

PubMed

A novel sensor array using seven room-temperature ionic liquids (ILs) as sensing materials and a quartz crystal microbalance (QCM) as a transducer was developed for the detection of organic vapors at ambient and elevated temperatures. Ethanol, dichloromethane, benzene, and heptane were selected as representative gas analytes for various kinds of environmental pollutants and common industrial solvents. The QCM/IL sensors responded proportionately and reversibly to the organic vapor concentrations (i.e., ethanol, heptane, and benzene) in the gas phase from 0 to 100% saturation at room and elevated temperatures (e.g., 120 degrees C) but deviated from this linear relationship at high concentrations for dichloromethane, a highly volatile compound. Linear discriminant analysis was used to analyze the sensing patterns. Excellent classifications were obtained for both known and unknown concentrations of vapor samples. The correct classifications were 100% for known concentration samples and 96% for samples with unknown concentrations. Thermodynamics and ATR-FT-IR studies were conducted to understand specific molecular interactions, the strength of the interaction between ILs and organic vapors, and the degree of ordering that takes place upon dissolution of the vapors in ILs. The different response intensity of the QCM/IL sensors to the organic vapors depends on the different solubilities of organic vapors in ILs and varying molecular/ion interactions between each organic vapor and IL. The diverse set of IL studied showed selective responses due to structural differences. Therefore, a sensor array of ILs would be able to effectively differentiate different vapors in pattern recognitions, facilitating discrimination by their distinctive patterns in response to organic vapors in both room and high temperatures. PMID:17007524

Jin, Xiaoxia; Yu, Lei; Garcia, Diego; Ren, Rex X; Zeng, Xiangqun

2006-10-01

396

Evaluation of flush mounted hot-film sensors for skin friction reduction measurements in viscoelastic polymer solutions  

Microsoft Academic Search

The performance of flush mounted hot-film sensors for mean wall shear stress measurement in turbulent flows of dilute drag reducing polymer solution is evaluated. A series of pipe flow experiments were conducted to compare the level of skin friction reduction measured by hot-film sensors with values determined from the pipe pressure drop. Water calibrated hot-film sensors consistently underestimate the wall

W. L. Harbison; H. L. Petrie

1990-01-01

397

Improvement of ultrasonic atomizer method for deposition of gas-sensing film on QCM  

Microsoft Academic Search

We report on improved ultrasonic atomizer method of depositing the sensing films on quartz crystal microbalance (QCM) sensors. The main objectives of the present work were minimizing the sensor-to-sensor response variation, improving the sensing film stability, and reducing amount of materials used during coating (reducing time of coating). In order to achieve the goals, we have redesigned and refabricated large

Bartosz Wyszynski; Agustin Gutierrez Galvez; Takamichi Nakamoto

2007-01-01

398

A novel gas ionization sensor using Pd nanoparticle-capped ZnO  

PubMed Central

A novel gas ionization sensor using Pd nanoparticle-capped ZnO (Pd/ZnO) nanorods as the anode is proposed. The Pd/ZnO nanorod-based sensors, compared with the bare ZnO nanorod, show lower breakdown voltage for the detected gases with good sensitivity and selectivity. Moreover, the sensors exhibit stable performance after more than 200 tests for both inert and active gases. The simple, low-cost, Pd/ZnO nanorod-based field-ionization gas sensors presented in this study have potential applications in the field of gas sensor devices.

2011-01-01

399

Effects of Activation Energy to Transient Response of Semiconductor Gas Sensor  

NASA Astrophysics Data System (ADS)

The smell classifiable gas sensor will be desired for many applications such as gas detection alarms, process controls for food production and so on. We have tried to realize the sensor using transient responses of semiconductor gas sensor consisting of tin dioxide and pointed out that the sensor gave us different transient responses for kinds of gas. Results of model calculation showed the activation energy of chemical reaction on the sensor surface strongly depended on the transient response. We tried to estimate the activation energies by molecular orbital calculation with SnO2 Cluster. The results show that there is a liner relationship between the gradient of the transient responses and activation energies for carboxylic and alcoholic gases. Transient response will be predicted from activation energy in the same kind of gas and the smell discrimination by single semiconductor gas sensor will be realized by this relationship.

Fujimoto, Akira; Ohtani, Tatsuki

400

Micro-Machined Thin Film Sensor Arrays For The Detection Of H2, Containing Gases, And Method Of Making And Using The Same  

Microsoft Academic Search

The present invention provides a hydrogen sensor including a thin film sensor element formed by metal organic chemical vapor deposition (MOCVD) or physical vapor deposition (PVD), on a micro-hotplate structure. The thin film sensor element includes a film of a hydrogen-interactive metal film that reversibly interacts with hydrogen to provide a correspondingly altered response characteristic, such as optical transmissivity, electrical

DiMeo Jr. Frank; Thomas H. Baum

2003-01-01

401

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.

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

402

H 2 selective gas sensor based on SnO 2  

Microsoft Academic Search

A highly selective H2 gas sensor was developed based on a ‘hot wire type’ gas sensor commercially available. Tin oxide semiconductor was sintered in a bead (0.5 mm in diameter) covering over a platinum wire (0.02 mm in diameter) coil. The gas sensor was operated by a bridge electric circuit. A dense layer of ?0.1 mm in depth near the

A. Katsuki; K. Fukui

1998-01-01

403

Flashback Detection Sensor for Hydrogen Augmented Natural Gas Combustion  

SciTech Connect

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

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

2007-05-01

404

Optical waveguide lightmode spectroscopy (OWLS) as a sensor for thin film and quantum dot corrosion.  

PubMed

Optical waveguide lightmode spectroscopy (OWLS) is usually applied as a biosensor system to the sorption-desorption of proteins to waveguide surfaces. Here, we show that OWLS can be used to monitor the quality of oxide thin film materials and of coatings of pulsed laser deposition synthesized CdSe quantum dots (QDs) intended for solar energy applications. In addition to changes in data treatment and experimental procedure, oxide- or QD-coated waveguide sensors must be synthesized. We synthesized zinc stannate (Zn(2)SnO(4)) coated (Si,Ti)O(2) waveguide sensors, and used OWLS to monitor the relative mass of the film over time. Films lost mass over time, though at different rates due to variation in fluid flow and its physical effect on removal of film material. The Pulsed Laser Deposition (PLD) technique was used to deposit CdSe QD coatings on waveguides. Sensors exposed to pH 2 solution lost mass over time in an expected, roughly exponential manner. Sensors at pH 10, in contrast, were stable over time. Results were confirmed with atomic force microscopy imaging. Limiting factors in the use of OWLS in this manner include limitations on the annealing temperature that maybe used to synthesize the oxide film, and limitations on the thickness of the film to be studied. Nevertheless, the technique overcomes a number of difficulties in monitoring the quality of thin films in-situ in liquid environments. PMID:23443400

Yu, Hao; Eggleston, Carrick M; Chen, Jiajun; Wang, Wenyong; Dai, Qilin; Tang, Jinke

2012-12-13

405

Optical Waveguide Lightmode Spectroscopy (OWLS) as a Sensor for Thin Film and Quantum Dot Corrosion  

PubMed Central

Optical waveguide lightmode spectroscopy (OWLS) is usually applied as a biosensor system to the sorption-desorption of proteins to waveguide surfaces. Here, we show that OWLS can be used to monitor the quality of oxide thin film materials and of coatings of pulsed laser deposition synthesized CdSe quantum dots (QDs) intended for solar energy applications. In addition to changes in data treatment and experimental procedure, oxide- or QD-coated waveguide sensors must be synthesized. We synthesized zinc stannate (Zn2SnO4) coated (Si,Ti)O2 waveguide sensors, and used OWLS to monitor the relative mass of the film over time. Films lost mass over time, though at different rates due to variation in fluid flow and its physical effect on removal of film material. The Pulsed Laser Deposition (PLD) technique was used to deposit CdSe QD coatings on waveguides. Sensors exposed to pH 2 solution lost mass over time in an expected, roughly exponential manner. Sensors at pH 10, in contrast, were stable over time. Results were confirmed with atomic force microscopy imaging. Limiting factors in the use of OWLS in this manner include limitations on the annealing temperature that maybe used to synthesize the oxide film, and limitations on the thickness of the film to be studied. Nevertheless, the technique overcomes a number of difficulties in monitoring the quality of thin films in-situ in liquid environments.

Yu, Hao; Eggleston, Carrick M.; Chen, Jiajun; Wang, Wenyong; Dai, Qilin; Tang, Jinke

2012-01-01

406

Gas sensor characterization at low concentrations of natural oils  

NASA Astrophysics Data System (ADS)

Inhalation of essential oils can be used in aromatherapy due to their activating or relaxing effects. The study of these effects requires behavioral measurements on living subjects, by varying the nature and also the quantity of the volatile substances to be present in the atmosphere. So, to permit the evaluation of therapeutic effects of a variety of natural oils, we propose to develop an automatic diffusion/detection system capable to create an ambient air with low stabilized concentration of chosen oil. In this work, we discuss the performance of an array of eight gas sensors to discriminate low and constant concentrations of a chosen natural oil.

Sambemana, H.; Siadat, M.; Lumbreras, M.

2009-05-01

407

Porous Silicon-Based Gas Sensors and Miniature Hydrogen Cells  

NASA Astrophysics Data System (ADS)

The current-voltage (I-V) characteristics of Au/porous silicon (PS)/Si Schottky-type structures in humid, CO, and H2S gas atmospheres were investigated. It was found that the gas atmosphere influences the I-V characteristics, particularly the reverse current in Au/PS/Si and Au/PS structures. The reverse current in the H2S atmosphere was 103 times larger than that in room-temperature (300 K) air [45% relative humidity (RH)]. The generation of an open-circuit voltage (up to 480 mV) at the Au/PS interface in humid, CO, and H2S atmospheres was detected. The humidity- and gas-stimulated effect of voltage generation in the Au/PS/Si structures was reversible with a response time of 60 s. The quite high sensitivities to humidity, CO, and H2S (about 9 mV/RH, 4 mV/ppm, and 2 mV/ppm, respectively) indicate the possibility of using the obtained Au/PS/Si structures as both gas sensors and miniature hydrogen fuel cells. The mechanism for the gas-stimulated generation of electricity in the Au/PS structures is discussed and is considered to be similar to that of the proton exchange membrane in hydrogen fuel cells.

Dzhafarov, Tayyar; Yuksel, Sureyya Aydin; Lus, Cigdem Oruc

2008-10-01

408

Sensors  

NSDL National Science Digital Library

Electronic sensors exist in many facets of our lives, from measuring operating conditions of our vehicles to adjusting the temperature of our homes. They can even mean the difference between life and death when used to monitor patients in emergency rooms. Even though sensors work transparently in their multitude of functions, their importance cannot be understated.Sensorland (1) has basic descriptions of a wide variety of sensors and related concepts. Out of the 50 items in the list, some have full technical reports that explain physical processes, while others consist of succinct explanations of a device's operation. The site covers sensors that measure everything from atmospheric pressure to the pH value of liquid solutions. In September 2002, the US Army conducted exercises using the zNose, a sensor that can quickly and quantitatively analyze any smell or vapor. This paper (2) provides a complete technical description of the zNose. Several more documents, including the press release of the Army's use of the device, can be found on the Electronic Sensor Technology homepage. In a related story from Sandia National Laboratories, the SnifferSTAR (3) could be especially useful in case of a terrorist gas attack. The short article briefly discusses how the invention works, with an emphasis on its characteristics of low power consumption and rapid analysis. Environmental Research Aircraft and Sensor Technology (4) is a NASA program to develop unmanned aerial vehicles capable of conducting advanced scientific studies. A number of aircraft are highlighted on the program's Web site, many of which are designed for long-term flights or potentially dangerous missions. The February 2003 cover story of Sensors magazine (5) is inertial sensing technology made from microelectromechanical systems (MEMS). The article discusses the applications of MEMS in accelerometers and gyroscopes, as well as explaining some of the theory behind these devices. A streaming video presentation, given in May 2002, can be viewed from this site (6). The hour-long talk introduces Sensor Webs, a network of tiny sensors connected by wireless technology that can be scattered over a large area to gather scientific data. Sensors can even be used in performing arts, as is shown in this paper from the Massachusetts Institute of Technology Media Lab (7). The authors propose using motion sensors to monitor hundreds of performers simultaneously, thereby allowing for much improved lighting and music responses. In the wake of the Space Shuttle Columbia tragedy, a great deal of attention was given to the intermittent and failing sensors on the shuttle minutes before it broke apart. This document from NASA shows the status of several sensors at various intervals in the shuttle's decent (8).

Leske, Cavin.

2003-01-01

409

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

410

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

411

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.

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

2013-01-01

412

Gas-leak localization using distributed ultrasonic sensors  

NASA Astrophysics Data System (ADS)

We propose an ultrasonic gas leak localization system based on a distributed network of sensors. The system deploys highly sensitive miniature Micro-Electro-Mechanical Systems (MEMS) microphones and uses a suite of energy-decay (ED) and time-delay of arrival (TDOA) algorithms for localizing a source of a gas leak. Statistical tools such as the maximum likelihood (ML) and the least squares (LS) estimators are used for approximating the source location when closed-form solutions fail in the presence of ambient background nuisance and inherent electronic noise. The proposed localization algorithms were implemented and tested using a Java-based simulation platform connected to four or more distributed MEMS microphones observing a broadband nitrogen leak from an orifice. The performance of centralized and decentralized algorithms under ED and TDOA schemes is analyzed and compared in terms of communication overhead and accuracy in presence of additive white Gaussian noise (AWGN).

Huseynov, Javid; Baliga, Shankar; Dillencourt, Michael; Bic, Lubomir; Bagherzadeh, Nader

2009-03-01

413

TiO(2)/LiCl-based nanostructured thin film for humidity sensor applications.  

PubMed

A simple and straightforward method of depositing nanostructured thin films, based on LiCl-doped TiO(2), on glass and LiNbO(3) sensor substrates is demonstrated. A spin-coating technique is employed to transfer a polymer-assisted precursor solution onto substrate surfaces, followed by annealing at 520°C to remove organic components and drive nanostructure formation. The sensor material obtained consists of coin-shaped nanoparticles several hundred nanometers in diameter and less than 50 nm thick. The average thickness of the film was estimated by atomic force microscopy (AFM) to be 140 nm. Humidity sensing properties of the nanostructured material and sensor response times were studied using conductometric and surface acoustic wave (SAW) sensor techniques, revealing reversible signals with good reproducibility and fast response times of about 0.75 s. The applicability of this nanostructured film for construction of rapid humidity sensors was demonstrated. Compared with known complex and expensive methods of synthesizing sophisticated nanostructures for sensor applications, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), this work presents a relatively simple and inexpensive technique to produce SAW humidity sensor devices with competitive performance characteristics. PMID:21284374

Buvailo, Andrii I; Xing, Yangjun; Hines, Jacqueline; Dollahon, Norman; Borguet, Eric

2011-02-01

414

Study of the discharge gas trapping during thin film growth  

Microsoft Academic Search

Discharge gas trapping in thin films produced by sputtering is known to be due to high energy neutrals bouncing back from the cathode. Qualitatively, the phenomenon is enhanced by raising the discharge voltage and is strongly dependent on the atomic masses of the discharge gas and of the cathode material. In addition to these known effects it is shown that,

Sergio Calatroni; S Amorosi; M Anderle; Cristoforo Benvenuti; J Carver; P Chiggiato; H Neupert; W Vollenberg

1999-01-01

415

Gas-jet synthesis of silver-polymer films  

NASA Astrophysics Data System (ADS)

A new method of gas-jet deposition of metal-polymer composites with simultaneous deposition of polymer matrices and silver clusters from two gas-dynamic sources is presented. Specific features of cluster deposition and the properties of composite films are described. Results on the antibacterial effect of silver-polymer composites on stock cultures of various bacteria are reported.

Rebrov, A. K.; Safonov, A. I.; Timoshenko, N. I.; Varnek, V. A.; Oglezneva, I. M.; Kosolobov, S. S.

2010-07-01

416

Optical waveguide sensor based on a porous anodic alumina/aluminum multilayer film.  

PubMed

An optical waveguide sensor was fabricated by forming a multilayer film made by porous anodic alumina (PAA) and Al layers on a glass substrate. The fabricated sensor system was based on the monitoring of a waveguide coupling mode, which is sensitive to the change in the refractive index of the PAA layer caused by collection of target molecules into the pores of the PAA layer. The PAA/Al multilayer film was formed by partial anodization of an Al film deposited on the glass substrate, and the waveguide coupling mode was examined by measuring angular spectra (reflectivity dependence on the incident angle of monitoring light; green He-Ne laser, 534.5 nm). A deep and sharp waveguide coupling dip was obtained for the PAA/Al multilayer system where the thicknesses of the PAA and Al layers were 200 and 17 nm, respectively. The optical sensor response of the PAA/Al multilayer system was compared to the responses of a surface plasmon resonance (SPR) sensor made by a Au thin film on a SF10 glass substrate. It was inferred that the optical waveguide sensor made by the PAA/Al multilayer could detect a smaller change in the refractive index of a solution, and it provided higher resolution than the SPR sensor. The sensor response for a change in the complex refractive index of the PAA layer was examined next, and it was found that the optical waveguide sensor was sensitive to the change in the imaginary part of the complex refractive index rather than the change in the real part. This result indicated that the sensitivity of the optical waveguide sensor could be improved by using the light absorption of a target compound. PMID:19049367

Yamaguchi, Akira; Hotta, Kazuhiro; Teramae, Norio

2009-01-01

417

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

418

TOPICAL REVIEW: Nitride and oxide semiconductor nanostructured hydrogen gas sensors  

NASA Astrophysics Data System (ADS)

In this paper, we discuss the progress of nitride and oxide semiconductor nanostructures for hydrogen gas sensing. The use of catalyst metal coatings on GaN, InN and ZnO nanowires is found to greatly enhance the detection sensitivity. Pt- and Pd-coated GaN nanowires biased at small voltages show large changes in currents upon exposure to H2 gas at concentrations in the ppm range. Improvements in growth techniques for InN nanostructures have produced nanobelts and nanorods capable of hydrogen detection down to 20 ppm after catalyst coating. Functionalized ZnO nanorods were also investigated for hydrogen detection, but did not generate a relative response as high as that for the nitride-based sensors. All sensors tested exhibited no response at room temperature upon exposure to various other gases including O2, C2H5, N2O and CO2. The high surface-to-volume ratio of nanowires and the ability to use simple contact fabrication schemes make them attractive for hydrogen sensing applications.

Wright, J. S.; Lim, Wantae; Norton, D. P.; Pearton, S. J.; Ren, F.; Johnson, Jason L.; Ural, Ant

2010-02-01

419

Infrared sensor for CVD deposition of dielectric films.  

National Technical Information Service (NTIS)

Infrared emission (IRE) spectra were obtained from two borophosphosilicate glass (BPSG) thin-film sample sets. The first set consisted of 21 films deposited on undoped silicon wafers, and the second set consisted of 9 films deposited on patterned and dope...

T. M. Niemczyk J. E. Franke S. Zhang D. M. Haaland

1994-01-01

420

Gas sensors development using supercritical fluid technology to detect the ripeness of bananas  

Microsoft Academic Search

This work reports the development of gas sensors with three different techniques applied to sensor coating with conducting polymer polyaniline (PANI) by: in situ polymerization, RESS (rapid expansion of supercritical solutions) of polyaniline doped with dodecyl benzene sulphonic acid (DBSA) in pressurized fluid, and precipitation. The two latter sensors were obtained through micro\\/nanoparticle deposition onto interdigitated line patterns of graphite

C. Steffens; E. Franceschi; F. C. Corazza; P. S. P. Herrmann Jr.; J. Vladimir Oliveira

2010-01-01

421

A Bio-Inspired Pattern Recognition System for Tin-Oxide Gas Sensor Applications  

Microsoft Academic Search

In this paper, a bio-inspired pattern recognition system for tin-oxide gas sensor applications is proposed. To mimic the biological olfactory system, temperature modulation is first used to virtually increase the number of sensors by periodically sampling the sensors' response at different temperatures. A convex microhotplate is used in order to improve the thermal properties of the structure enabling efficient temperature

Aicha Beya Far; Farid Flitti; Bin Guo; Amine Bermak

2009-01-01

422

New miniaturized SAW-sensor array for organic gas detection driven by multiplexed oscillators  

Microsoft Academic Search

The use of sensor arrays with polymer-coated surface acoustic wave (SAW) devices as the key element for analytical sensor systems is a very promising technique for organic gas detection in process or quality control. In this work we present a new improved array of eight SAW sensors showing up reduced size, sampling volume and assembling costs. Moreover, its most important

M Rapp; J Reibel; A Voigt; M Balzer; O Bülow

2000-01-01

423

Three-Axis Acceleration Sensor Using Polyurea Films  

NASA Astrophysics Data System (ADS)

Focusing on the possibilities of polyurea as an acceleration sensor with characteristics such as flexibility, durability against large deformation, good linearity, and capability of deposition in dryprocess and insolubility in organic solvent, we first fabricated a cantilever acceleration sensor and a three-axis acceleration sensor. The output voltage in the large-strain region is measured using a polyurea cantilever sensor attached to a beryllium copper substrate. The results show that output voltages have good linearity for large strains up to 1%. This value is much larger than the breakdown limit of lead zirconate titanate. Second, we fabricated a polyurea three-axis acceleration sensor. The sensor consists of an insulation layer of polyurea on the cross beam substrate of phosphor bronze, a bottom aluminum electrode, a polyurea active layer, and four top aluminum electrodes. The experimental results for harmonic acceleration show that the sensor works as expected. The cross-axis sensitivity of the polyurea sensor was less than 8%, which is close to that of conventional microelectromechanical system sensors.

Tabaru, Masaya; Nakazawa, Marie; Nakamura, Kentaro; Ueha, Sadayuki

2008-05-01

424

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

425

Development of backscattering sensor for gas distribution pipes. Final report, November 1990-September 1992  

SciTech Connect

A breadboard gamma backscattering sensor for measuring the wall thickness of gas distribution pipes has been developed. The sensor was originally intended to be mounted on an internal inspection system separately developed for GRI. Two prototypes of the sensor, and a computer controlled miniaturized electronic board, were constructed and tested. The first prototype was a low resolution sensor intended to obtain information averaged over a relatively large area of the pipe surface. The second prototype allows more detailed scans, at a sacrifice in speed. Both sensors were intended to provide information on the wall thickness of gas distribution pipes 4 to 6 inches in diameter.

Borgonovi, G.M.

1993-02-01

426

In situ measurement of gas composition changes in radio frequency plasmas using a quartz sensor  

NASA Astrophysics Data System (ADS)

A simple method using a quartz sensor (Q-sensor) was developed to observe gas composition changes in radio frequency (rf) plasmas. The output depends on the gases' absolute pressure, molecular weight, and viscosity. The pressure-normalized quartz sensor output depends only on the molecular weight and viscosity of the gas. Consequently, gas composition changes can be detected in the plasmas if a sensor can be used in the plasmas. Influences imparted by the plasmas on the sensor, such as those by reactive particles (e.g., radicals and ions), excited species, electrons, temperature, and electric potentials during measurements were investigated to test the applicability of this quartz sensor measurement to plasma. The Q-sensor measurement results for rf plasmas with argon, hydrogen, and their mixtures are reproducible, demonstrating that the Q-sensor measurement is applicable for plasmas. In this work, pressure- and temperature-normalized Q-sensor output (NQO) were used to obtain the gas composition information of plasma. Temperature-normalization of the Q-sensor output enabled quartz sensor measurements near plasma electrodes, where the quartz sensor temperature increases. The changes in NQO agreed with results obtained by gas analysis using a quadrupole mass spectrometer. Results confirmed that the change in NQO is mainly attributable to changes in the densities and kinds of gas molecules in the plasma gas phase, not by other extrinsic influences of plasma. For argon, hydrogen, and argon-hydrogen plasmas, these changes correspond to reduction in nitrogen, production of carbon monoxide, and dissociation of hydrogen molecules, respectively. These changes in NQO qualitatively and somewhat quantitatively agreed with results obtained using gas analysis, indicting that the measurement has a potential application to obtain the gas composition in plasmas without disturbing industrial plasma processes.

Suzuki, Atsushi; Nonaka, Hidehiko

2009-09-01

427

In situ measurement of gas composition changes in radio frequency plasmas using a quartz sensor.  

PubMed

A simple method using a quartz sensor (Q-sensor) was developed to observe gas composition changes in radio frequency (rf) plasmas. The output depends on the gases' absolute pressure, molecular weight, and viscosity. The pressure-normalized quartz sensor output depends only on the molecular weight and viscosity of the gas. Consequently, gas composition changes can be detected in the plasmas if a sensor can be used in the plasmas. Influences imparted by the plasmas on the sensor, such as those by reactive particles (e.g., radicals and ions), excited species, electrons, temperature, and electric potentials during measurements were investigated to test the applicability of this quartz sensor measurement to plasma. The Q-sensor measurement results for rf plasmas with argon, hydrogen, and their mixtures are reproducible, demonstrating that the Q-sensor measurement is applicable for plasmas. In this work, pressure- and temperature-normalized Q-sensor output (NQO) were used to obtain the gas composition information of plasma. Temperature-normalization of the Q-sensor output enabled quartz sensor measurements near plasma electrodes, where the quartz sensor temperature increases. The changes in NQO agreed with results obtained by gas analysis using a quadrupole mass spectrometer. Results confirmed that the change in NQO is mainly attributable to changes in the densities and kinds of gas molecules in the plasma gas phase, not by other extrinsic influences of plasma. For argon, hydrogen, and argon-hydrogen plasmas, these changes correspond to reduction in nitrogen, production of carbon monoxide, and dissociation of hydrogen molecules, respectively. These changes in NQO qualitatively and somewhat quantitatively agreed with results obtained using gas analysis, indicting that the measurement has a potential application to obtain the gas composition in plasmas without disturbing industrial plasma processes. PMID:19791966

Suzuki, Atsushi; Nonaka, Hidehiko

2009-09-01

428

Studies of thin film chemical sensors using the quartz crystal microbalance  

NASA Astrophysics Data System (ADS)

The quartz crystal microbalance (QCM) is emerging as a powerful new tool in sensor technology. In the course of this work, the QCM is used to study solvent and ion transport in poly(vinyl chloride) (PVC) ion-selective electrode (ISE) membranes and as a base for thin film analytical sensors for specific ionic species in solution. Thin (approximately 1.5 micrometer) PVC-based ISE membranes swell in solution due to solvent and/or ion uptake, the resultant mass change in the film causes the resonant frequency of the quartz crystal to decrease. The frequency measurements obtained when exposing ISE-type membranes containing neutral carrier type ionophores to analyte-containing solutions allow one to approximate the mass of solvent and analyte ions that entered the films during sensor operation.

Meyer, Howard R., Jr.

1990-08-01

429

Transient response of piezoelectric thin-film vibration sensor under pulse excitation  

NASA Astrophysics Data System (ADS)

We present an analytical model to describe the transient response of a piezoelectric thin-film vibration sensor under pulse excitation. The structure of the thin-film vibration sensor consists of four suspended flexural piezoelectric lead zirconate titanate-on-silicon beam transducers and a central seismic mass. The model takes into account the effect of device geometry and materials properties of the piezoelectric thin film. The relationships between the dynamic behavior and voltage sensitivity with the device's structure are established. It is found that with the increase of initial vibration magnitude U0 and reciprocal time constant ? (?=1/?) of the excitation, the maximum voltage sensitivity increases, and the maximum output voltage decreases with the increase of the resonance frequency. When damping is taken into account, the output voltage of the device under pulse excitation is simply an exponentially decaying function of time. The results can be readily applied for design and fabrication of the on-chip vibration sensor or accelerometer.

Yang, Zhaochun; Wang, Qing-Ming

2006-01-01

430

Wet Chemical Synthesis and Screening of Thick Porous Oxide Films for Resistive Gas Sensing Applications  

Microsoft Academic Search

A method of wet chemical synthesis suitable for high throughput and combinatorial applications has been developed for the synthesis of porous resistive thick- film gas sensors. This method is based on the robot-controlled application of unstable metal oxide suspensions on an array of 64 inter-digital electrodes positioned on an Al2O3 substrate. SnO2, WO3, ZrO2, TiO2, CeO2, In2O3 and Bi2O3 were

Gerald Frenzer; Andreas Frantzen; Daniel Sanders; Ulrich Simon; Wilhelm F. Maier

2006-01-01

431

Enhanced gas sensing of Au nanocluster-doped or -coated zinc oxide thin films  

NASA Astrophysics Data System (ADS)

We demonstrated that doping or covering with Au nanoclusters boosts gas sensing effectiveness of optical metal oxide sensors. The sensing response of pulsed laser deposited ZnO films as sensing element was tested by m-line technique for low concentration (1000 ppm) of butane in environmental N2. The optical interrogation was performed for three types of coatings: undoped ZnO, undoped ZnO structures partially covered with Au nanoclusters, or obtained from Au (0.5 wt %) doped ZnO targets. Nanocluster coating tripled the sensitivity, while doping resulted in an increase of up to 45% as compared with simple structures.

Socol, G.; Axente, E.; Ristoscu, C.; Sima, F.; Popescu, A.; Stefan, N.; Mihailescu, I. N.; Escoubas, L.; Ferreira, J.; Bakalova, S.; Szekeres, A.

2007-10-01

432

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

PubMed Central

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

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

2010-01-01

433

Thin film heat flux sensors for accurate transient and unidirectional heat transfer analysis  

NASA Astrophysics Data System (ADS)

Heat flux measurement is needed in many heat transfer studies. For the best unbiased heat flux sensors (HFS), the heat flux is obtained using temperature measurements at different locations and also an inverse heat conduction method (function specification...) in order to calculate the heat flux. Systematic errors can come from the uncertainty in the wire thermocouples locations and from errors in the knowledge of distances between two consecutive wire thermocouples. The main idea in this work is to use thin film thermoresistances deposited on a flexible thin polymer substrate instead of wire thermocouples welded on metallic sample. The interest of using thin film thermoresistances instead of wire thermocouples is a lower disturbance due to the smaller thickness of the thin film sensors (typically less than 1?m) and a much better knowledge of the distances between the different thin film thermoresistances which are precisely defined in the mask used for the metallic thin film pattern fabrication. In this paper, we present the fabrication of the new heat flux sensor with thin film thermoresistances, the study of the effect of the self heating (due to Joule effect in thermoresistances) and the performances of this new HFS with the comparison with classical HFS using wire thermocouples. For this study, a symmetric experimental setup is used with metallic samples equipped with an etched foil heater and both classical and new HFS. For several heating conditions, it appears that a better accuracy is always obtained with the new HFS using thin film thermoresistances.

Azerou, B.; Garnier, B.; Lahmar, J.

2012-11-01

434

Comparison of potentiometric enzyme sensors for urea and penicillin-G: differential thick-film sensors versus classical electrodes  

Microsoft Academic Search

A comparative study of urease and penicillinase biosensors was performed in which different transducers were compared, i.e. pH glass electrodes, macroscopic ion-selective electrodes and thick-film transducers. For enzyme immobilization onto the transducers aqueous dispersion polymers were used in all cases in this work. Since these sensors are based on potentiometric measurements the lack of a classical reference electrode when solid

Christian Eppelsheim; Ralph Aubeck; Norbert Hampp

1995-01-01

435

Laboratory Connections: Gas Monitoring Transducers: Relative Humidity Sensors.  

ERIC Educational Resources Information Center

Explains the operation of five relative humidity sensors: psychrometer, hair hygrometer, resistance hygrometer, capacitance hygrometer, and resistance-capacitance hygrometer. Outlines the theory behind the electronic sensors and gives computer interfacing information. Lists sensor responses for calibration. (MVL)

Powers, Michael H.; Hull, Stacey E.

1988-01-01

436

A MEMS Complete Blood Count Sensor with Vanes for Reduction in Influence of Electrolysis Gas  

NASA Astrophysics Data System (ADS)

To develop a miniature complete blood count (CBC) analyzer for point-of-care testing (POCT), a MEMS CBC sensor based on the impedance method is discussed. A novel MEMS CBC sensor that is fabricated through a simple photolithography process using SU-8 is realized. However, the fabricated sensor exhibits a noisy output signal due to electrolysis gas. The relationship between the noise and the gas is revealed through microscopic observation and finite element method (FEM) simulation. To solve the problem of electrolysis gas, an improved MEMS CBC sensor with vanes is developed. The improved sensor is unaffected by electrolysis gas. Moreover, the signal stability of the sensor and the signals detected for latex particles are successfully evaluated.

Tanabe, Rikiya; Hata, Seiichi; Shimokohbe, Akira

437

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

438

Hydrogen sensor based on side-polished fiber Bragg gratings coated with thin palladium film  

Microsoft Academic Search

A new type of hydrogen sensor based on a side-polished fiber Bragg grating (FBG) coated with thin palladium film was demonstrated experimentally. The used FBG with the reflectivity of 90% is fabricated in a hydrogen-loaded single-mode fiber (SMF-28) by using the phase mask writing technique of a KrF excimer laser. The experimental results show that proposed sensor can be applied

Chuen-Lin Tien; Hong-Wei Chen; Wen-Fung Liu; Shou-Shan Jyu; Shane-Wen Lin; Yung-Sen Lin

2008-01-01

439

Ultra-low-power polymer thin film encapsulated carbon nanotube thermal sensors  

Microsoft Academic Search

A novel polymer thin film embedded carbon nanotube (PECNT) sensor was developed for ultra-low-power micro thermal sensing. The basic fabrication process of this sensor includes AC electrophoretic manipulation of multi-walled carbon nanotubes (MWNT) bundles on a silicon substrate and embedding them inside parylene C layers to provide a robust protection for the bundled MWNTs. This encapsulation process ensures that the

Carmen K. M. Fung; Wen J. Li

2004-01-01

440

Development of techniques for fabrication of film probe sensor assembly. [PWR; BWR  

Microsoft Academic Search

Pulsed laser welding and brazing techniques were developed for fabrication of sensors designed to measure liquid film properties in out-of-reactor safety tests that simulate a loss-of-coolant accident in a pressurized-water nuclear reactor. These sensors were made possible by a unique ceramic-to-metal seal system based on a cermet insulator and a brazing filler metal, both developed at ORNL. This seal system

1982-01-01

441

Parametric Analysis of Acoustic Emission Signals for Evaluating Damage in Composites Using a PVDF Film Sensor  

Microsoft Academic Search

With the increased utilization of advanced composites in strategic industries, the concept of Structural Health Monitoring\\u000a (SHM) with its inherent advantages is gaining ground over the conventional methods of NDE and NDI. The most attractive feature\\u000a of this concept is on-line evaluation using embedded sensors. Consequently, development of methodologies with identification\\u000a of appropriate sensors such as PVDF films becomes the

H. N. Bar; M. R. Bhat; C. R. L. Murthy

2005-01-01

442

Breath-by-breath measurement of carbon dioxide using a plastic film optical sensor  

Microsoft Academic Search

An optical sensor has been developed for breath-by-breath gaseous CO2 analysis. The detector is based on a general formulation described in previous work where a phase-transfer agent, tetraoctyl ammonium hydroxide, is used to incorporate a hydrophilic pH-sensitive dye into a hydrophobic plastic film to create an effectively solid-state colorimetric sensor. In this work the formulation has been modified to yield

Andrew Mills; Anne Lepre; Lorraine Wild

1997-01-01

443

Embedding of micro thin film strain sensors in sapphire by diffusion bonding  

Microsoft Academic Search

Advanced ceramics have been increasingly used for various manufacturing processes. The current sensors used in ceramic tools are difficult to reliably provide thermomechanical measurements in or near the ceramic tool-workpiece interface. Thin film micro sensors could be embedded---thus avoiding direct contact with workpieces---at critical locations without interfering with normal manufacturing operation of the ceramic tool. However, little research has been

Hongseok Choi; Hiromi Konishi; Huifang Xu; Xiaochun Li

2007-01-01

444

Optofluidic glucose sensor utilizing an epoxy-based, transparent dry film resist  

Microsoft Academic Search

An enzymatic, fluorescent glucose sensor was constructed with a novel epoxy-based, optically-transparent dry film resist (PerMX 3000 series, DuPont). This material was utilized as the main active material for fluidic structure and optical interrogation. This sensor was based on the enzymatic reaction of glucose oxidase (GOD) and utilized a ruthenium complex fluorophore as the reporting agent. Both the oxygen-sensitive ruthenium

Zhan Gao; Sijia Gong; Chang-Soo Kim; David B. Henthorn

2011-01-01

445

Acoustic sensor technology  

Microsoft Academic Search

The recent development in monolithic devices has enabled a breakthrough in the applications of acoustic sensors in navigation and communications signal processing. A piezoelectric thin film material, such as ZnO, AlN or PZT, permits both acoustoelectric SAW and semiconductor electronic device components to be fabricated on the same monolithic substrate. Here, we discuss acoustic sensor applications such as pressure, gas

M. E. Motamedi

1994-01-01

446

A preliminary study on detection of muscle activity using a flexible AlN piezoelectric thin film sensor  

Microsoft Academic Search

Muscle activity can be used to generate control signals for prosthetic devices and human-assisting manipulators. Recently, a novel method has been developed to measure muscle movement using a flexible piezoelectric thin film sensor, which is made of oriented aluminum nitride (AlN) film. However, rigorous relationship between muscle activity and the sensor's output has not been clarified. As a preliminary study,

Nan Bu; Osamu Fukuda; Naohiro Ueno; Masahiro Inoue

2009-01-01

447

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

448

Solid State Sensors for Selective Gas Detection at High Temperatures—Principles and Challenges  

Microsoft Academic Search

To satisfy demands for in-situ monitoring of high-temperature processes, ever more sophisticated sensors are required. Advances in achieving improved sensitivity and selectivity are expected from miniaturization and integration of active electronic components thereby enabling new sensor principles or simultaneous application of different sensor principles.First, conventional resistive and potentiometric sensors are reviewed with respect to their stability and gas selectivity at

Michal Schulz; Denny Richter; Jan Sauerwald; Holger Fritze

2010-01-01

449

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

450

A combinatorial technique for the search of solid state gas sensor materials  

Microsoft Academic Search

A complete high throughput assembly for the search for electrochemical sensor materials is described. It is a primary screening device, whose sole purpose is to locate most efficiently new materials with potential sensor properties. The set-up consists of a gas tight reactor for the sensor libraries, an IR-camera, a switching multimeter for dc-resistance measurements, a test gas supply array for

Jens Scheidtmann; Andreas Frantzen; Gerald Frenzer; Wilhelm F. Maier

2005-01-01

451

Solid electrolyte gas sensors based on cyclic voltammetry with one active electrode  

NASA Astrophysics Data System (ADS)

Solid state gas sensors are cost effective, small, rugged and reliable. Typically electrochemical solid state sensors operate in either potentiometric or amperometric mode. However, a lack of selectivity is sometimes a shortcoming of such sensors. It seems that improvements of selectivity can be obtained in case of the electrocatalytic sensors, which operate in cyclic voltammetry mode. Their working principle is based on acquisition of an electric current, while voltage ramp is applied to the sensor. The current-voltage response depends in a unique way on the type and concentration of ambient gas. Most electrocatalytic sensors have symmetrical structure. They are in a form of pellets with two electrodes placed on their opposite sides. Electrochemical reactions occur simultaneously on both electrodes. In this paper results for sensors with only one active electrode exposed to ambient gas are presented. The other electrode was isolated from ambient gas with dielectric sealing. This sensor construction allows application of advanced measuring procedures, which permit sensor regeneration acceleration. Experiments were conducted on Nasicon sensors. Properties of two sensors, one with one active electrode and second with symmetrical structure, used for the detection of mixtures of NO2 and synthetic air are compared.

Jasinski, G.; Jasinski, P.

2011-10-01

452

The Role of a Photoresist Film on Reverse Gas Plasma Etching of Chromium Films  

NASA Astrophysics Data System (ADS)

The role of a photoresist film on reverse gas plasma etching of chromium photomask plates has been studied. The variation of etching profiles has been observed using SEM techniques. It is speculated that a WO3 layer on the chromium film forms a masking layer to the etching and that the WO3 layer can be removed by decomposition of the photoresist film in the plasma. A study of the relation between photoresist thickness and etching time has shown that there is an optimum photoresist thickness for each WO3 concentration in the chromium film.

Yamazaki, Teruhiko; Suzuki, Yoshiki; Uno, Jun; Nakata, Hidefumi

1980-07-01

453

Infrared sensor for CVD deposition of dielectric films  

SciTech Connect

Infrared emission (IRE) spectra were obtained from two borophosphosilicate glass (BPSG) thin-film sample sets. The first set consisted of 21 films deposited on undoped silicon wafers, and the second set consisted of 9 films deposited on patterned and doped (product) wafers. The IRE data were empirically modeled using partial least-squares calibration to simultaneously quantify four BPSG thin-film properties. The standard errors of the determinations when modeling the 21 monitor wafers were film thickness, and 1.9{degree}C for temperature. The standard errors of the determinations based on the product wafers were 0.13 wt % each for B and P content, 120 {angstrom} for film thickness, and 5.9 C for temperature.

Niemczyk, T.M.; Franke, J.E.; Zhang, S. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Chemistry; Haaland, D.M. [Sandia National Labs., Albuquerque, NM (United States)

1994-06-01

454

Glassy spectral gas sensors based on the immobilized indicators  

NASA Astrophysics Data System (ADS)

A number of color absorption and luminescence indicators being dispersed within a porous matrix have been investigated by means of spectral techniques. As a support for the indicator molecules served a mesoporous silica glass of Vycor type (pore size of 7.5 nm) which was transparent to the light and permeable to the ambient gases and vapors. The selected immobilized indicators have revealed the well-defined spectral sensitivity to certain components of an atmosphere or other gas mixture. After a proper chemical and thermal treatment these indicators have gained high selectivity of spectral response on an individual gas appearing in the ambients, the observed spectral changes have demonstrated its reversibility. The indicators immobilized within the porous glass turned out to be mostly advantageous as applied in the colorimetric sensors and anlyzyers, sepcifically in the automated remote air monitoring systems. Some of the essential parameters of the developed portable individual gas analyzers and remote multicomponent monitoring systems with use of fiber optic guides are reported.

Novikov, Alexander G.; Zemskii, Vladimir I.

1995-09-01

455

Detection of dilute nitrogen dioxide and thickness effect of tungsten oxide thin film sensors  

Microsoft Academic Search

WO3 thin film sensors have been fabricated by suspension dropping on SiO2\\/Si substrate equipped with Au microelectrodes, and subjected to the detection of dilute NO2 less than ppm level. The WO3 thin film with the thickness of ca. 0.6?m showed the extremely high sensitivity to dilute NO2 at 200°C (for example, S=9.4 to 0.2ppm NO2). The Au electrodes were visible

Jun Tamaki; Atsushi Hayashi; Yoshifumi Yamamoto; Masao Matsuoka

2003-01-01

456

Ceramic thin films by sol-gel processing as novel materials for integrated humidity sensors  

Microsoft Academic Search

Thin films based on 10 at% alkali-doped TiO2 and on iron with very large humidity sensitivity were prepared using a sol-gel technique. Prototype humidity sensors were prepared by depositing metal alkoxide solutions onto Al2O3 substrates with comb-type Au electrodes, by dip-coating and heating in air. Heating to 300°C produces continuous films, free of porosity, which appear as layers covering the

Enrico Traversa; Guglielmina Gnappi; Angelo Montenero; Gualtiero Gusmano

1996-01-01

457

Polyimide membrane with ZnO piezoelectric thin film pressure transducers as a differential pressure liquid flow sensor  

Microsoft Academic Search

Fabrication and characterization of ZnO thin film piezoelectric sensors on a polyimide membrane is presented in this paper. As a test device a differential pressure liquid flow sensor has been fabricated. We discuss new material combinations for the fabrication of the test devices. The pressure sensor membrane is a thin polyimide sheet bonded to a silicon wafer and the sensing

Andreas Kuoni; Raphaël Holzherr; Marc Boillat; Nico F. de Rooij

2003-01-01

458

Assessment of the wall shear stress measurement with arrayed micro hot-film sensors in a turbulent channel flow  

Microsoft Academic Search

Arrayed micro hot-film sensors for the measure- ment of the streamwise and spanwise wall shear stresses were developed and evaluated in a turbulent channel flow. The bandwidth of the sensor is found to be much narrower than previous estimates in the lit- erature. A numerical analysis of the unsteady thermal field around the sensor chip is made in order to

Takashi Yoshino; Yuji Suzuki; Nobuhide Kasagi; Shoji Kamiunten

2001-01-01

459

Dual-tier thin film polymer polarization imaging sensor.  

PubMed

Traditional imaging systems capture and replicate the imaged environment in terms of color and intensity. One important property of light, which the human eye is blind to and is ignored by traditional imaging systems, is polarization. In this paper we present a novel, low power imaging sensor capable of recording the optical properties of partially linearly polarized light in real-time. The imaging sensor combines polymer polarization filters with a CMOS image sensor in order to compute the first three Stokes parameters at the focal plane. The imaging array contains 100 x 100 pixels and consumes 48 mW at 30 fps. PMID:20940825

Gruev, Viktor; Van der Spiegel, Jan; Engheta, Nader

2010-08-30

460

Ultrasonic Measurements on Quench—Condensed Noble Gas Films  

Microsoft Academic Search

Quench–condensed noble gas films are a simple model system for studying the elastic properties of polycrystalline or amorphous solids at low temperatures. We have investigated the temperature dependence of the sound velocity dv\\/v and attenuation a of quench–condensed polycrystalline Ar, Ne, and HD films using surface acoustic waves at 800 MHz. Up to 0.7 K the sound velocity of all

G. Weiss; K. Eschenröder; J. Classen; S. Hunklinger

1998-01-01