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Sample records for ammonia gas sensing

  1. Room Temperature Ammonia Gas Sensing Characteristics of Co3O4

    Directory of Open Access Journals (Sweden)

    P.N. Shelke

    2011-01-01

    Full Text Available Room temperature ammonia gas-sensing characteristics of Co3O4 pellet sensor are reported in this paper. For this purpose, Co3O4 powder is prepared by a route of simple precipitation + heating at 800 °C/2 hr. The as-prepared powder is characterized by using X-ray diffraction and scanning electron microscopy. The ammonia gas-sensing properties of Co3O4 pellets made at various loads of 3, 5, 7 & 9 ton and at constant time = 4 min. are measured using home-built static gas sensing system. The characterization studies revealed that the cobalt oxide particles formed are cubic spinel Co3O4, highly pure and spherical in shape. The particle size distribution is found to be nearly uniform with average particle size ~ 1 µm. The ammonia gas sensing properties of Co3O4 pellet sensor are found to be good. The highest sensitivities – S.F. = 175 and 358 are found at ~ 25 ppm and 250 ppm concentrations of ammonia gas respectively for the Co3O4 pellet sensor made at the load = 3 ton. Further, an admirable repeatability and reversibility in the ammonia gas sensing characteristics are observed for all the Co3O4 pellet sensors. The average response time of 4.0 min. and recovery time of 3.0 min. are obtained for all the Co3O4 pellet sensors.

  2. Spectroscopic and electrical sensing mechanism in oxidant-mediated polypyrrole nanofibers/nanoparticles for ammonia gas

    Science.gov (United States)

    Ishpal; Kaur, Amarjeet

    2013-05-01

    Ammonia gas sensing mechanism in oxidant-mediated polypyrrole (PPy) nanofibers/nanoparticles has been studied through spectroscopic and electrical investigations. PPy nanofibers/nanoparticles have been synthesized by chemical oxidation method in the presence of various oxidizing agents such as ammonium persulfate (APS), potassium persulfate (PPS), vanadium pentoxide (V2O5), and iron chloride (FeCl3). Scanning electron microscopy study revealed that PPy nanofibers of about 63, 71 and 79 nm diameters were formed in the presence of APS, PPS, V2O5, respectively, while PPy nanoparticles of about 100-110 nm size were obtained in the presence of FeCl3 as an oxidant. The structural investigations and confirmation of synthesis of PPy were established through Fourier transform infrared and Raman spectroscopy. The gas sensing behavior of the prepared PPy samples is investigated by measuring the electrical resistance in ammonia environment. The observed gas sensing response ( δR R × 100 ) at 100 ppm level of ammonia is 4.5 and 18 % for the samples prepared with oxidizing agents FeCl3 and APS, respectively, and by changing the ammonia level from 50 to 300 ppm, the sensing response varies from 4.5 to 11 % and 10 to 39 %, respectively. Out of all four samples, the PPy nanofibers prepared in the presence of APS have shown the best sensing response. The mechanism of gas sensing response of the PPy samples has been investigated through Raman spectroscopy study. The decrease of charge carrier concentration through reduction of polymeric chains has been recognized through Raman spectroscopic measurements recorded in ammonia environment.

  3. Spectroscopic and electrical sensing mechanism in oxidant-mediated polypyrrole nanofibers/nanoparticles for ammonia gas

    Energy Technology Data Exchange (ETDEWEB)

    Ishpal; Kaur, Amarjeet, E-mail: amarkaur@physics.du.ac.in [University of Delhi, Department of Physics and Astrophysics (India)

    2013-05-15

    Ammonia gas sensing mechanism in oxidant-mediated polypyrrole (PPy) nanofibers/nanoparticles has been studied through spectroscopic and electrical investigations. PPy nanofibers/nanoparticles have been synthesized by chemical oxidation method in the presence of various oxidizing agents such as ammonium persulfate (APS), potassium persulfate (PPS), vanadium pentoxide (V{sub 2}O{sub 5}), and iron chloride (FeCl{sub 3}). Scanning electron microscopy study revealed that PPy nanofibers of about 63, 71 and 79 nm diameters were formed in the presence of APS, PPS, V{sub 2}O{sub 5}, respectively, while PPy nanoparticles of about 100-110 nm size were obtained in the presence of FeCl{sub 3} as an oxidant. The structural investigations and confirmation of synthesis of PPy were established through Fourier transform infrared and Raman spectroscopy. The gas sensing behavior of the prepared PPy samples is investigated by measuring the electrical resistance in ammonia environment. The observed gas sensing response ({Delta}R/Rx100) at 100 ppm level of ammonia is {approx}4.5 and 18 % for the samples prepared with oxidizing agents FeCl{sub 3} and APS, respectively, and by changing the ammonia level from 50 to 300 ppm, the sensing response varies from {approx}4.5 to 11 % and {approx}10 to 39 %, respectively. Out of all four samples, the PPy nanofibers prepared in the presence of APS have shown the best sensing response. The mechanism of gas sensing response of the PPy samples has been investigated through Raman spectroscopy study. The decrease of charge carrier concentration through reduction of polymeric chains has been recognized through Raman spectroscopic measurements recorded in ammonia environment.

  4. Ammonia Gas Sensing Behavior of Tanninsulfonic Acid Doped Polyaniline-TiO2 Composite

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    Venu Gopal Bairi

    2015-10-01

    Full Text Available A highly active tannin doped polyaniline-TiO2 composite ammonia gas sensor was developed and the mechanism behind the gas sensing activity was reported for the first time. A tanninsulfonic acid doped polyaniline (TANIPANI-titanium dioxide nanocomposite was synthesized by an in situ polymerization of aniline in the presence of tanninsulfonic acid and titanium dioxide nanoparticles. X-ray diffraction and thermogravimetric analysis were utilized to determine the incorporation of TiO2 in TANIPANI matrix. UV-Visible and infrared spectroscopy studies provided information about the electronic interactions among tannin, polyaniline, and TiO2. Scanning electron microscopy (SEM along with energy dispersive X-ray spectroscopy (EDS and atomic force microscopy (AFM surface analysis techniques were used to investigate the metal oxide dispersions inside polyaniline matrix. Gas sensors were prepared by spin coating solutions of TANIPANI-TiO2 and TANIPANI composites onto glass slides. Sensors were tested at three different concentrations (20 ppm, 40 ppm, and 60 ppm of ammonia gas at ambient temperature conditions by measuring the changes in surface resistivity of the films with respect to time. Ammonia gas sensing plots are presented showing the response values, response times and recovery times. The TANIPANI-TiO2 composite exhibited better response and shorter recovery times when compared to TANIPANI control and other polyaniline composites that have been reported in the literature. For the first time a proposed mechanism of gas sensing basing on the polaron band localization and its effects on the gas sensing behavior of polyaniline are reported.

  5. Investigation of Pristine Graphite Oxide as Room-Temperature Chemiresistive Ammonia Gas Sensing Material

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    Alexander G. Bannov

    2017-02-01

    Full Text Available Graphite oxide has been investigated as a possible room-temperature chemiresistive sensor of ammonia in a gas phase. Graphite oxide was synthesized from high purity graphite using the modified Hummers method. The graphite oxide sample was investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetry and differential scanning calorimetry. Sensing properties were tested in a wide range of ammonia concentrations in air (10–1000 ppm and under different relative humidity levels (3%–65%. It was concluded that the graphite oxide–based sensor possessed a good response to NH3 in dry synthetic air (ΔR/R0 ranged from 2.5% to 7.4% for concentrations of 100–500 ppm and 3% relative humidity with negligible cross-sensitivity towards H2 and CH4. It was determined that the sensor recovery rate was improved with ammonia concentration growth. Increasing the ambient relative humidity led to an increase of the sensor response. The highest response of 22.2% for 100 ppm of ammonia was achieved at a 65% relative humidity level.

  6. Thiourea-treated graphene aerogel as a highly selective gas sensor for sensing of trace level of ammonia

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    Alizadeh, Taher, E-mail: talizadeh@ut.ac.ir [Department of Analytical Chemistry, Faculty of Chemistry, University College of Science, University of Tehran, P.O. Box 14155-6455, Tehran (Iran, Islamic Republic of); Ahmadian, Farzaneh [Department of Applied Chemistry, Faculty of Science, University of Mohaghegh Ardabili, Daneshgah Street, P.B179, 56199-11367 Ardabil (Iran, Islamic Republic of)

    2015-10-15

    As a result of this study, a new and simple method was proposed for the fabrication of an ultra sensitive, robust and reversible ammonia gas sensor. The sensing mechanism was based upon the change in electrical resistance of a graphene aerogel as a result of sensor exposing to ammonia. Three-dimensional graphene hydrogel was first synthesized via hydrothermal method in the absence or presence of various amounts of thiourea. The obtained material was heated to obtain aerogel and then it was used as ammonia gas sensor. The materials obtained were characterized using different techniques such as Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thiourea-treated graphene aerogel was more porous (389 m{sup 2} g{sup −1}) and thermally unstable and exhibited higher sensitivity, shorter response time and better selectivity toward ammonia gas, compared to the aerogel produced in the absence of thiourea. Thiourea amount, involved in the hydrogel synthesis step, was found to be highly effective factor in the sensing properties of finally obtained aerogel. The sensor response time to ammonia was short (100 s) and completely reversible (recovery time of about 500 s) in ambient temperature. The sensor response to ammonia was linear between 0.02 and 85 ppm and its detection limit was found to be 10 ppb (3S/N). - Highlights: • An ammonia gas sensor with ppb level determination capability was proposed. • A new procedure has been introduced for gas sensor fabrication by graphene hydrogel. • Thiourea-treated graphene aerogel was used as excellent ammonia gas sensor.

  7. Influence of dielectric constant of polymerization medium on processability and ammonia gas sensing properties of polyaniline

    Indian Academy of Sciences (India)

    Partha Pratim Sengupta; Pradip Kar; Basudam Adhikari

    2011-04-01

    Polyaniline (PANI) was synthesized by the oxidation of aniline hydrochloride in the presence of ammonium persulphate and hydrochloric acid. The polymerization reaction was carried out in several batches in different solvent media by changing the volume ratio of ,-dimethyl formamide (DMF) and water as binary solvent mixture. The dielectric constant of the polymerizationmedium for each batch reaction was determined by measuring the capacitance with change in frequency. The UV spectra of the synthesized polyaniline solutions helped us to optimize the ratio of the binary solvent to get sufficient polymer growth and processability. Thin film of processable polyaniline was then deposited on glass slides coated with polyvinyl alcohol (PVA) crosslinked with maleic anhydride (MA). FTIR and XRD studies of the coated film were also done. AFM studies further helped in the morphological study of the film deposited. Finally, conductivity and ammonia gas-sensing property of the polyaniline film were also studied.

  8. Thiourea-treated graphene aerogel as a highly selective gas sensor for sensing of trace level of ammonia.

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    Alizadeh, Taher; Ahmadian, Farzaneh

    2015-10-15

    As a result of this study, a new and simple method was proposed for the fabrication of an ultra sensitive, robust and reversible ammonia gas sensor. The sensing mechanism was based upon the change in electrical resistance of a graphene aerogel as a result of sensor exposing to ammonia. Three-dimensional graphene hydrogel was first synthesized via hydrothermal method in the absence or presence of various amounts of thiourea. The obtained material was heated to obtain aerogel and then it was used as ammonia gas sensor. The materials obtained were characterized using different techniques such as Fourier transform infra red spectroscopy (FT-IR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thiourea-treated graphene aerogel was more porous (389 m(2) g(-1)) and thermally unstable and exhibited higher sensitivity, shorter response time and better selectivity toward ammonia gas, compared to the aerogel produced in the absence of thiourea. Thiourea amount, involved in the hydrogel synthesis step, was found to be highly effective factor in the sensing properties of finally obtained aerogel. The sensor response time to ammonia was short (100 s) and completely reversible (recovery time of about 500 s) in ambient temperature. The sensor response to ammonia was linear between 0.02 and 85 ppm and its detection limit was found to be 10 ppb (3S/N).

  9. LPG ammonia and nitrogen dioxide gas sensing properties of nanostructured polypyrrole thin film

    Energy Technology Data Exchange (ETDEWEB)

    Bagul, Sagar B., E-mail: nano.sbbagul@gmail.com; Upadhye, Deepak S.; Sharma, Ramphal, E-mail: rps.phy@gmail.com [Thin Film and Nanotechnology Laboratory, Department of Nanotechnology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad (India)

    2016-05-06

    Nanostructured Polypyrrole thin film was synthesized by easy and economic chemical oxidative polymerization technique on glass at room temperature. The prepared thin film of Polypyrrole was characterized by optical absorbance study by UV-visible spectroscopy and electrical study by I-V measurement system. The optical absorbance spectrum of Polypyrrole shows two fundamental peaks in region of 420 and 890 nm, which confirms the formation of Polypyrrole on glass substrate. The I-V graph of nanostructured Polypyrrole represents the Ohmic nature. Furthermore, the thin film of Polypyrrole was investigated by Scanning electron microscopy for surface morphology study. The SEM micrograph represents spherical nanostructured morphology of Polypyrrole on glass substrate. In order to investigate gas sensing properties, 100 ppm of LPG, Ammonia and Nitrogen Dioxide were injected in the gas chamber and magnitude of resistance has been recorded as a function of time in second. It was observed that nanostructured Polypyrrole thin film shows good sensing behavior at room temperature.

  10. Temperature Optimized Ammonia and Ethanol Sensing Using Ce Doped Tin Oxide Thin Films in a Novel Flow Metric Gas Sensing Chamber

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    K. Govardhan

    2016-01-01

    Full Text Available A simple process of gas sensing is represented here using Ce doped tin oxide nanomaterial based thin film sensor. A novel flow metric gas chamber has been designed and utilized for gas sensing. Doping plays a vital role in enhancing the sensing properties of nanomaterials. Ce doped tin oxide was prepared by hydrothermal method and the same has been used to fabricate a thin film for sensing. The microstructure and morphology of the prepared materials were analysed by SEM, XRD, and FTIR analysis. The SEM images clearly show that doping can clamp down the growth of the large crystallites and can lead to large agglomeration spheres. Thin film gas sensors were formed from undoped pure SnO2 and Ce doped SnO2. The sensors were exposed to ammonia and ethanol gases. The responses of the sensors to different concentrations (50–500 ppm of ammonia and ethanol at different operating temperatures (225°C–500°C were studied. Results show that a good sensitivity towards ammonia was obtained with Ce doped SnO2 thin film sensor at an optimal operating temperature of 325°C. The Ce doped sensor also showed good selectivity towards ammonia when compared with ethanol. Pure SnO2 showed good sensitivity with ethanol when compared with Ce doped SnO2 thin film sensor. Response time of the sensor and its stability were also studied.

  11. An in-line Mach-Zehnder Interferometer Using Thin-core Fiber for Ammonia Gas Sensing With High Sensitivity

    Science.gov (United States)

    Huang, Xinyue; Li, Xueming; Yang, Jianchun; Tao, Chuanyi; Guo, Xiaogang; Bao, Hebin; Yin, Yanjun; Chen, Huifei; Zhu, Yuhua

    2017-01-01

    Ammonia is an important indicator among environmental monitoring parameters. In this work, thin-core fiber Mach-Zehnder interferometer deposited with poly (acrylic acid) (PAA), poly (allyamine hydrochloride) (PAH) and single-walled carbon nanotubes (SWCNTs-COOH) sensing film for the detection of ammonia gas has been presented. The thin-core fiber modal interferometer was made by fusion splicing a small section of thin-core fiber (TCF) between two standard single mode fibers (SMF). A beam propagation method (BPM) is employed for the design of proposed interferometer and numerical simulation. Based on the simulation results, interferometer with a length of 2 cm of thin-core fiber is fabricated and experimentally studied. (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film is deposited on the outer surface of thin-core fiber via layer-by-layer (LbL) self-assembly technique. The gas sensor coated with (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film towards NH3 gas exposure at concentrations range from 1 to 960 ppm are analyzed and the sensing capability is demonstrated by optical spectrum analyzer (OSA). Experimental results show that the characteristic wavelength shift has an approximately linear relationship in the range 1–20 ppm, which is in accordance with the numerical simulation. Thus, this paper reveals the potential application of this sensor in monitoring low concentration NH3 gas. PMID:28378783

  12. An in-line Mach-Zehnder Interferometer Using Thin-core Fiber for Ammonia Gas Sensing With High Sensitivity

    Science.gov (United States)

    Huang, Xinyue; Li, Xueming; Yang, Jianchun; Tao, Chuanyi; Guo, Xiaogang; Bao, Hebin; Yin, Yanjun; Chen, Huifei; Zhu, Yuhua

    2017-04-01

    Ammonia is an important indicator among environmental monitoring parameters. In this work, thin-core fiber Mach-Zehnder interferometer deposited with poly (acrylic acid) (PAA), poly (allyamine hydrochloride) (PAH) and single-walled carbon nanotubes (SWCNTs-COOH) sensing film for the detection of ammonia gas has been presented. The thin-core fiber modal interferometer was made by fusion splicing a small section of thin-core fiber (TCF) between two standard single mode fibers (SMF). A beam propagation method (BPM) is employed for the design of proposed interferometer and numerical simulation. Based on the simulation results, interferometer with a length of 2 cm of thin-core fiber is fabricated and experimentally studied. (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film is deposited on the outer surface of thin-core fiber via layer-by-layer (LbL) self-assembly technique. The gas sensor coated with (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film towards NH3 gas exposure at concentrations range from 1 to 960 ppm are analyzed and the sensing capability is demonstrated by optical spectrum analyzer (OSA). Experimental results show that the characteristic wavelength shift has an approximately linear relationship in the range 1-20 ppm, which is in accordance with the numerical simulation. Thus, this paper reveals the potential application of this sensor in monitoring low concentration NH3 gas.

  13. Gas-Sensing Devices Based on Zn-Doped NiO Two-Dimensional Grainy Films with Fast Response and Recovery for Ammonia Molecule Detection.

    Science.gov (United States)

    Wang, Jian; Wei, Xiaowei; Wangyang, Peihua

    2015-12-01

    Zn-doped NiO two-dimensional grainy films on glass substrates are shown to be an ammonia-sensing material with excellent comprehensive performance, which could real-time detect and monitor ammonia (NH3) in the surrounding environment. The morphology and structure analysis indicated that the as-fabricated semiconductor films were composed of particles with diameters ranging from 80 to 160 nm, and each particle was composed of small crystalline grain with a narrow size about 20 nm, which was the face-centered cubic single crystal structure. X-ray diffraction peaks shifted toward lower angle, and the size of the lattice increased compared with undoped NiO, which demonstrated that zinc ions have been successfully doped into the NiO host structure. Simultaneously, we systematically investigated the gas-sensing properties of the Zn-doped NiO sensors for NH3 detection at room temperature. The sensor based on doped NiO sensing films gave four to nine times faster response and four to six times faster recovery speeds than those of sensor with undoped NiO films, which is important for the NiO sensor practical applications. Moreover, we found that the doped NiO sensors owned outstanding selectivity toward ammonia.

  14. Excellent ammonia sensing performance of gas sensor based on graphene/titanium dioxide hybrid with improved morphology

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    Ye, Zongbiao; Tai, Huiling; Guo, Rui; Yuan, Zhen; Liu, Chunhua; Su, Yuanjie; Chen, Zhi; Jiang, Yadong

    2017-10-01

    Reduced graphene oxide (rGO)-titanium dioxide (TiO2) hybrid material has been prepared through a facile hydrothermal method for ammonia detection at room temperature. The combined characterizations including X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis) and scanning electron microscopy (SEM) indicated the successful formation of rGO-TiO2 hybrid. It also showed that the morphology of graphene sheets was greatly improved to become porous and undulating due to introduction of synthetic titanium dioxide. Accordingly, the hybrid-based sensor showed much more excellent sensing properties in comparison to that of bare graphene film sensor. The mechanism for the improvement could be ascribed to the synergetic effect between rGO sheets and TiO2 nanospheres, specifically, the enrichment of active adsorption sites on account of the supporting function of TiO2 nanospheres.

  15. Optical Gas Sensing of Ammonia and Amines Based on Protonated Porphyrin/TiO2 Composite Thin Films

    Science.gov (United States)

    Castillero, Pedro; Roales, Javier; Lopes-Costa, Tânia; Sánchez-Valencia, Juan R.; Barranco, Angel; González-Elipe, Agustín R.; Pedrosa, José M.

    2016-01-01

    Open porous and transparent microcolumnar structures of TiO2 prepared by physical vapour deposition in glancing angle configuration (GLAD-PVD) have been used as host matrices for two different fluorescent cationic porphyrins, 5-(N-methyl 4-pyridyl)-10,15,20-triphenyl porphine chloride (MMPyP) and meso-tetra (N-methyl 4-pyridyl) porphine tetrachloride (TMPyP). The porphyrins have been anchored by electrostatic interactions to the microcolumns by self-assembly through the dip-coating method. These porphyrin/TiO2 composites have been used as gas sensors for ammonia and amines through previous protonation of the porphyrin with HCl followed by subsequent exposure to the basic analyte. UV–vis absorption, emission, and time-resolved spectroscopies have been used to confirm the protonation–deprotonation of the two porphyrins and to follow their spectral changes in the presence of the analytes. The monocationic porphyrin has been found to be more sensible (up to 10 times) than its tetracationic counterpart. This result has been attributed to the different anchoring arrangements of the two porphyrins to the TiO2 surface and their different states of aggregation within the film. Finally, there was an observed decrease of the emission fluorescence intensity in consecutive cycles of exposure and recovery due to the formation of ammonium chloride inside the film. PMID:28025570

  16. Ammonia Optical Sensing by Microring Resonators

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    Passaro, Vittorio M. N.; Dell'Olio, Francesco; De Leonardis, Francesco

    2007-01-01

    A very compact (device area around 40 μm2) optical ammonia sensor based on a microring resonator is presented in this work. Silicon-on-insulator technology is used in sensor design and a dye doped polymer is adopted as sensing material. The sensor exhibits a very good linearity and a minimum detectable refractive index shift of sensing material as low as 8×10-5, with a detection limit around 4 ‰.

  17. Design Ammonia Gas Detection System by Using Optical Fiber Sensor

    Directory of Open Access Journals (Sweden)

    Dr. Bushra. R. Mhdi

    2013-07-01

    Full Text Available Design study and construction of Ammonia gas detection using a fiber as a sensor to based on evanescent wave sensing technique was investigated. Multi-mode fiber type (PCS with core diameter (600μm and (50cm length used where plastic clad was removed by chemical etching for effective sensing area which coated with sol-gel film to enhance its absorption characteristics to evanescent wave around the optical spectrum emitted from halogen lamp measurements through different temperature rang (25-60oc with and without air using as a carrier to ammonia molecules are investigated. Finally sensing efficiency are monitored to ammonia gas it affected to different temperature and environmental condition are studied and our result are compatible to scientific publishes

  18. Nitrocarburizing in ammonia-hydrocarbon gas mixtures

    DEFF Research Database (Denmark)

    Pedersen, Hanne; Christiansen, Thomas; Somers, Marcel A. J.

    2011-01-01

    The present work investigates the possibility of nitrocarburising in ammonia-acetylene-hydrogen and ammonia-propene-hydrogen gas mixtures, where unsaturated hydrocarbon gas is the carbon source during nitrocarburising. Consequently, nitrocarburising is carried out in a reducing atmosphere...... microscopy and X-ray diffraction analysis. It is shown that the use of unsaturated hydrocarbon gas in nitrocarburising processes is a viable alternative to traditional nitrocarburising methods....

  19. Ammonia gas permeability of meat packaging materials.

    Science.gov (United States)

    Karim, Faris; Hijaz, Faraj; Kastner, Curtis L; Smith, J Scott

    2011-03-01

    Meat products are packaged in polymer films designed to protect the product from exterior contaminants such as light, humidity, and harmful chemicals. Unfortunately, there is almost no data on ammonia permeability of packaging films. We investigated ammonia permeability of common meat packaging films: low-density polyethylene (LDPE; 2.2 mil), multilayer polyolefin (MLP; 3 mil), and vacuum (V-PA/PE; 3 mil, 0.6 mil polyamide/2.4 mil polyethylene). The films were fabricated into 10 × 5 cm pouches and filled with 50 mL deionized water. Pouches were placed in a plexiglass enclosure in a freezer and exposed to 50, 100, 250, or 500 ppm ammonia gas for 6, 12, 24, and 48 h at -17 ± 3 °C and 21 ± 3 °C. At freezing temperatures, no ammonia residues were detected and no differences in pH were found in the water. At room temperature, ammonia levels and pH of the water increased significantly (P packaging materials have low ammonia permeability and protect meat products exposed to ammonia leaks during frozen storage.

  20. Nitrocarburising in ammonia-hydrocarbon gas mixtures

    DEFF Research Database (Denmark)

    Pedersen, Hanne; Christiansen, Thomas; Somers, Marcel A. J.

    2010-01-01

    The present work investigates the possibility of nitrocarburising in ammonia-acetylene-hydrogen and ammoniapropene- hydrogen gas mixtures, where unsaturated hydrocarbon gas is the carbon source during nitrocarburising. Consequently, nitrocarburising is carried out in a reducing atmosphere...... microscopy and X-ray diffraction analysis. It is shown that the use of unsaturated hydrocarbon gas in nitrocarburising processes is a viable alternative to traditional nitrocarburising methods....

  1. Development of Ammonia Gas Sensor Using Optimized Organometallic Reagent

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    J. Aubrecht

    2016-01-01

    Full Text Available Reliable, continuous, and spatially distributed monitoring of dangerous or irritating chemical substances belongs to standard functions of contemporary industrial and public security systems. Fiber-optic-based detection provides feasible platform to fulfill such aims. This paper deals with characterization of ammonia sensing elements based on multimode polysiloxane-clad silica-core optical fibers sensitized with 5-(4′-dioctylamino phenylimino quinoline-8-1 cobalt bromide complex reagent immobilized into the cross-linked polymer matrix from a proper mixture of organic solvents and a radical scavenger contributing to the desired long-term stability of optical properties. The applied sensing mechanism combines optical detection principle with chemical reaction of the reagent and ammonia resulting in changes in the visible near-infrared optical absorption spectrum of the cladding layer, influencing via evanescent optical field interactions the spectral distribution of the guided light intensity. Reaction kinetics of short fiber sections exposed to ammonia/nitrogen mixture of various ammonia concentrations is tested and evaluated. The obtained sensitivity, limit of detection, and forward response time of the prepared sensors amount to 1.52⁎10-5 ppm−1, 31 ppm, and 25 s, respectively. The obtained results are promising for fabrication of distributed fiber-optic sensors applicable to detection and location of ammonia gas leaks in industrial as well as general public premises.

  2. Ammonia Sensing Behaviors of TiO2-PANI/PA6 Composite Nanofibers

    Science.gov (United States)

    Wang, Qingqing; Dong, Xianjun; Pang, Zengyuan; Du, Yuanzhi; Xia, Xin; Wei, Qufu; Huang, Fenglin

    2012-01-01

    Titanium dioxide-polyaniline/polyamide 6 (TiO2-PANI/PA6) composite nanofibers were prepared by in situ polymerization of aniline in the presence of PA6 nanofibers and a sputtering-deposition process with a high purity titanium sputtering target. TiO2-PANI/PA6 composite nanofibers and PANI/PA6 composite nanofibers were fabricated for ammonia gas sensing. The ammonia sensing behaviors of the sensors were examined at room temperature. All the results indicated that the ammonia sensing property of TiO2-PANI/PA6 composite nanofibers was superior to that of PANI/PA6 composite nanofibers. TiO2-PANI/PA6 composite nanofibers had good selectivity to ammonia. It was also found that the content of TiO2 had a great influence on both the morphology and the sensing property of TiO2-PANI/PA6 composite nanofibers. PMID:23235446

  3. Ammonia Sensing Behaviors of TiO2-PANI/PA6 Composite Nanofibers

    Directory of Open Access Journals (Sweden)

    Fenglin Huang

    2012-12-01

    Full Text Available Titanium dioxide-polyaniline/polyamide 6 (TiO2-PANI/PA6 composite nanofibers were prepared by in situ polymerization of aniline in the presence of PA6 nanofibers and a sputtering-deposition process with a high purity titanium sputtering target. TiO2-PANI/PA6 composite nanofibers and PANI/PA6 composite nanofibers were fabricated for ammonia gas sensing. The ammonia sensing behaviors of the sensors were examined at room temperature. All the results indicated that the ammonia sensing property of TiO2-PANI/PA6 composite nanofibers was superior to that of PANI/PA6 composite nanofibers. TiO2-PANI/PA6 composite nanofibers had good selectivity to ammonia. It was also found that the content of TiO2 had a great influence on both the morphology and the sensing property of TiO2-PANI/PA6 composite nanofibers.

  4. Fiber Optic Detection of Ammonia Gas

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    L. Kalvoda

    2006-01-01

    Full Text Available Bathochromic shifts accompanying the formation of several bivalent metallic complexes containing 5-(4’-dimethylaminophenylimino quinolin-8-one (L1, and 7-chlore-5(4’-diethylamino-2-methylphenylimino quinolin-8-one (L2 ligands in ethanol solutions were evaluated by VIS-NIR spectroscopy. The [L1-Cu-L1] sulphide complex was selected as a reagent for further tests on optical fibres. Samples of multimode siloxane-clad fused-silica fibre were sensitized by diffusing an ethanol/chloroform solution of the dye into the cladding polymer, and tested by VIS-NIR optical spectroscopy (12 cm long fibre sections, and optical time domain reflectometry (OTDR; 20 ns laser pulses, wavelength 850 nm, 120 m long fibre sensitized within the interval 104–110 m. A well-resolved absorption band of the reagent could be identified in the absorption spectra of the fibres. After exposure to dry ammonia/nitrogen gas with increasing ammonia concentration (0–4000 ppm, the short fibre samples showed subsequent decay of NIR optical absorption; saturation was observed for higher ammonia levels. The concentration resolution r ? 50 ppm and forward response time t90 ? 30 sec were obtained within the interval 0–1000 ppm. The OTDR courses showed an enhancement of the back-scattered light intensity coming from the sensitized region after diffusion of the initial reagent, and decay after exposure to concentrated ammonia/nitrogen gas (10000 ppm.

  5. Ammonia detection of 1-D ZnO/polypyrrole nanocomposite: Effect of CSA doping and their structural, chemical, thermal and gas sensing behavior

    Science.gov (United States)

    Jain, Shilpa; Karmakar, Narayan; Shah, Akshara; Kothari, D. C.; Mishra, Satyendra; Shimpi, Navinchandra G.

    2017-02-01

    Nanocomposites of polypyrrole (PPy) with varying concentration of ZnO nanorods (ZnO NRs) were synthesized using in-situ oxidative polymerization technique. The prepared nanocomposites (PPy, PPy-ZnO and CSA doped PPy-ZnO) were studied for various oxidizing and reducing gases at room temperature and found to be more selective towards ammonia gas. Various concentrations of ZnO NRs in Ppy matrix were studied and 15% was found to be optimum in terms of sensor response (66% towards 120 ppm NH3). Further, with 15% doping of camphor sulphonic acid (CSA) in PPy-ZnO nanocomposite for 15% ZnO NRs in Ppy matrix, sensor response increased from 66 to 79% towards 120 ppm of NH3. Structural, Optical and thermal behavior of nanocomposites were studied using powder X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), UV-vis (UV-vis) absorption spectroscopy, room temperature Photoluminescence (PL) Spectroscopy, Thermo-gravimetric analysis (TGA) and Field Emission Scanning Electron Microscopy (FESEM). ZnO has been completely embedded inside the polymeric chains as observed from in SEM. Meanwhile, FT-IR spectra indicate better conjugation and interaction in nanocomposites. With CSA doping interaction grows stronger due to extended delocalization over π electrons leading to higher sensor response and with response time and recovery time of 24 s and 34 s respectively. CSA doped PPy-ZnO (15%) nanocomposites observed to be a potential candidate for ammonia detection at lower ppm level.

  6. Ammonia sensing system based on wavelength modulation spectroscopy

    Science.gov (United States)

    Viveiros, Duarte; Ferreira, João; Silva, Susana O.; Ribeiro, Joana; Flores, Deolinda; Santos, José L.; Frazão, Orlando; Baptista, José M.

    2015-06-01

    A sensing system in the near infrared region has been developed for ammonia sensing based on the wavelength modulation spectroscopy (WMS) principle. The WMS is a rather sensitive technique for detecting atomic/molecular species, presenting the advantage that it can be used in the near-infrared region by using the optical telecommunications technology. In this technique, the laser wavelength and intensity were modulated by applying a sine wave signal through the injection current, which allowed the shift of the detection bandwidth to higher frequencies where laser intensity noise was typically lower. Two multi-pass cells based on free space light propagation with 160 cm and 16 cm of optical path length were used, allowing the redundancy operation and technology validation. This system used a diode laser with an emission wavelength at 1512.21 nm, where NH3 has a strong absorption line. The control of the NH3 gas sensing system, as well as acquisition, processing and data presentation was performed.

  7. Biofilter Treating Ammonia Gas Using Agricultural Residues Media

    Directory of Open Access Journals (Sweden)

    Thaniya Kaosol

    2012-01-01

    Full Text Available Problem statement: Agricultural residues such as manure and sugarcane bagasse are wastes from agro-industry which has low value and requires some sustainable waste management method. In this research, a mixture of manure fertilizer and sugarcane bagasse is used as a biofilter media for an ammonia gas removal application. The aim of this research is to study the ammonia gas removal efficiency of such media. Approach: The experiments were conducted in laboratory-scale biofilters. Two inlet ammonia gas concentrations were used which are 500 and 1,000 ppm. Three ratios of manure fertilizer and sugarcane bagasse were studied including 1:3, 1:5 and 1:7 by volume. All experiments were conducted for a period of 40 days. Two Empty Bed Retention Time (EBRT of these experiments were used which is 39s and 78s. The moisture content of the biofilter media was maintained at 45-60% by adding water. Results: The maximum ammonia gas removal efficiency at 89.93% is observed from the following conditions: 500 ppm of the inlet ammonia gas concentration, the manure fertilizer and sugarcane bagasse mixture ratio of 1:5 and the EBRT of 78s. The important factors of the ammonia gas removal in biofiltration process are the inlet ammonia gas concentration and the EBRT. Conclusion: The experimental results showed that the mixture of manure fertilizer and sugarcane bagasse is an effective biofilter media for ammonia gas removal applications. However, the biofilter is more effective at low inlet ammonia gas concentration, while the ratio of manure fertilizer and sugarcane bagasse has no significant effect on the ammonia gas removal efficiency. Therefore, using both residues as biofilter media for ammonia gas removal application is an alternative sustainable way to such manage argo-industry waste.

  8. A Cyanine Dye Encapsulated Porous Fibrous Mat for Naked-Eye Ammonia Sensing.

    Science.gov (United States)

    Ji, Chendong; Ma, Lijing; Yin, Meizhen; Yang, Wantai; Pan, Kai

    2016-08-19

    Electrospun ultrathin fiber-based sensors are desirable because of their practicality and sensitivity. Ammonia-detection systems are in high demand in different areas, including the industrial and agricultural fields. However, current technologies rely on large and complex instruments that restrict their actual utilization. Herein, we report a flexible naked-eye ammonia sensor, the polylactic acid-cyanine (PLA-Cy) fibrous mat, which was fabricated by blending a carboxyl-functionalized cyanine dye (D1) into electospun PLA porous fibers. The sensing mat was shown to undergo a naked-eye-detectable color change from white to blue upon exposure to ammonia vapor. The mat showed high selectivity to ammonia gas with a detection limit of 3.3 ppm. Aggregated D1 was first encapsulated by PLA and was then ionized by NH3 . These mechanisms were examined by photophysical studies and scanning electron microscopy. The aggregation-deaggregation process of D1 in the PLA-Cy fibrous mat led to the color change. This work provides a facile method for the naked-eye detection of ammonia and a novel strategy for the use of organic dyes in ammonia sensing.

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

    Science.gov (United States)

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

    2013-12-15

    The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix. © 2013 Elsevier B.V. All rights reserved.

  10. The determination of ammonium in Kjeldahl digests using the gas-sensing ammonia electrode. Comparison of the direct method with the known-addition method.

    Science.gov (United States)

    Nubé, M; Van den Aarsen, C P; Giliams, J P; Hekkens, W T

    1980-01-31

    The efficacy of the ammonia electrode for analysis of the nitrogen content of a large series of Kjeldahl digests was investigated. By using this electrode, two methods for the measurement of ammonium concentrations were compared, the direct method and the known-addition method. When the direct method was used, a marked shift in the electrode potential occurred within a few hours, causing errors of 9-17% in the results. When the ammonium concentrations were calculated from the difference in electrode potential before and after addition of a known amount of an ammonium standard solution (known-addition method), it was possible to carry out reproducible measurements and the shift in the electrode potential did not influence the results. In two series of identical samples the coefficient of variation was respectively 1.45% and 0.80%.

  11. A spherical-structure based fiber sensor for simultaneous measurement of ammonia gas concentration and temperature

    Science.gov (United States)

    Han, Wei; Liu, Dejun; Lian, Xiaokang; Mallik, Arun Kumar; Wei, Fangfang; Sun, Lei; Farrell, Gerald; Semenova, Yuliya; Wu, Qiang

    2016-11-01

    A novel fiber sensor for simultaneous measurement of ammonia gas concentration and temperature is proposed. The sensor is fabricated from two sections of single-mode fiber which are cleaved and then a fusion splicer and which is then used to fabricate spherically shaped structures at the end facets. The fusion arc is used to soften the glass which naturally assumes a spherical shape due to surface tension. A short section of multimode fiber is then fusion spliced with the two spherical-shaped ends of the single mode fibers so both the core modes and the cladding modes of the multimode fiber are excited to create two kinds of interference dips: One is created by core modes only which is not sensitive to ammonia gas since the core is isolated by the cladding so the effective refractive index of the core does not change when the refractive index of the environment changes, The other dip is created by the coupling of the core mode and cladding mod, which with a suitable coating is sensitive to ammonia gas. Silica sol-gel was prepared and coated on the fiber surface as a sensing layer for detecting ammonia gas concentration. The experimental results show that the two dips have linear wavelength shift responses but with different sensitivities to ammonia gas concentration (5.03×10-4nm/ppm for dip1 and -2.5×10- 5nm/ppm for dip2) and temperature (0.0067 nm/ºC for dip1 and 0.0149 nm/ºC for dip2. By constructing a wavelength shifts matrix for the two dips vs. ammonia gas concentration and temperature, both the ammonia gas concentration and temperature can be measured simultaneously.

  12. Flame Spray Synthesis and Ammonia Sensing Properties of Pure α-MoO3 Nanosheets

    Directory of Open Access Journals (Sweden)

    Gagan Jodhani

    2016-01-01

    Full Text Available This paper highlights the flame spray synthesis of α-MoO3 using ammonium molybdate as precursor. The as-synthesized particles obtained were found to be ammonium molybdenum oxide and belonged to the triclinic crystal system. The particles crystallized to α-MoO3 upon thermal treatment at 500°C. Sensors were prepared by drop coating the powders onto alumina substrates coated with platinum electrodes and sensing tests were conducted evaluating the detection of ammonia concentrations down to ppb level concentration in air. The flame synthesized α-MoO3 based sensors show high sensitivity towards ammonia and may potentially be used in breath ammonia gas diagnostics.

  13. Ice nucleation of ammonia gas exposed montmorillonite mineral dust particles

    Directory of Open Access Journals (Sweden)

    A. Salam

    2007-01-01

    Full Text Available The ice nucleation characteristics of montmorillonite mineral dust aerosols with and without exposure to ammonia gas were measured at different atmospheric temperatures and relative humidities with a continuous flow diffusion chamber. The montmorillonite particles were exposed to pure (100% and diluted ammonia gas (25 ppm at room temperature in a stainless steel chamber. There was no significant change in the mineral dust particle size distribution due to the ammonia gas exposure. 100% pure ammonia gas exposure enhanced the ice nucleating fraction of montmorillonite mineral dust particles 3 to 8 times at 90% relative humidity with respect to water (RHw and 5 to 8 times at 100% RHw for 120 min exposure time within our experimental conditions. The percentages of active ice nuclei were 2 to 9 times higher at 90% RHw and 2 to 13 times higher at 100% RHw in 25 ppm ammonia exposed montmorillonite compared to unexposed montmorillonite. All montmorillonite particles are more efficient as ice nuclei with increasing relative humidities and decreasing temperatures. The activation temperature of montmorillonite exposed to 100% pure ammonia was 12°C higher than for unexposed montmorillonite particles at 90% RHw and 10°C higher at 100% RHw. In the 25 ppm ammonia exposed montmorillonite experiments, the activation temperature was 7°C warmer than unexposed montmorillonite at 100% RHw. Degassing does not reverse the ice nucleating ability of ammonia exposed montmorillonite mineral dust particles. This is the first experimental evidence that ammonia gas exposed montmorillonite mineral dust particles can enhance its activation as ice nuclei and that the activation can occur at temperatures warmer than –10°C where natural atmospheric ice nuclei are very scarce.

  14. Indium oxide thin film based ammonia gas and ethanol vapour sensor

    Indian Academy of Sciences (India)

    K K Makhija; Arabinda Ray; R M Patel; U B Trivedi; H N Kapse

    2005-02-01

    A sensor for ammonia gas and ethanol vapour has been fabricated using indium oxide thin film as sensing layer and indium tin oxide thin film encapsulated in poly(methyl methacrylate) (PMMA) as a miniature heater. For the fabrication of miniature heater indium tin oxide thin film was grown on special high temperature corning glass substrate by flash evaporation method. Gold was deposited on the film using thermal evaporation technique under high vacuum. The film was then annealed at 700 K for an hour. The thermocouple attached on sensing surface measures the appropriate operating temperature. The thin film gas sensor for ammonia was operated at different concentrations in the temperature range 323–493 K. At 473 K the sensitivity of the sensor was found to be saturate. The detrimental effect of humidity on ammonia sensing is removed by intermittent periodic heating of the sensor at the two temperatures 323K and 448 K, respectively. The indium oxide ethanol vapour sensor operated at fixed concentration of 400 ppm in the temperature range 293–393 K. Above 373 K, the sensor conductance was found to be saturate. With various thicknesses from 150–300 nm of indium oxide sensor there was no variation in the sensitivity measurements of ethanol vapour. The block diagram of circuits for detecting the ammonia gas and ethanol vapour has been included in this paper.

  15. Multilayer films of layered double hydroxide/polyaniline and their ammonia sensing behavior

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Dong-Mei; Guan, Mei-Yu; Xu, Qing-Hong; Guo, Ying, E-mail: guoying@mail.buct.edu.cn

    2013-11-15

    Highlights: • (ZnAl-LDH/PANI){sub n} multilayer films have been fabricated via a layer-by-layer assembly way. • The multilayer films have relatively ordered morphology and controllable thickness. • The multilayer films show extremely high selectivity to ammonia at room temperature. -- Abstract: This paper reports the fabrication of layered double hydroxide (LDH)/conductive polymer multilayer films by alternate assembly of exfoliated ZnAl-LDH nanosheets and polyaniline (PANI) on silicon wafer substrates using the layer-by-layer (LBL) deposition technology. UV–vis absorption spectroscopy indicates a stepwise and regular growth of the (LDH/PANI){sub n} multilayer films upon increasing deposition cycles. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrate that the surfaces of the films are microscopy smooth and uniform with a thickness of 2 nm per bilayer. Furthermore, the resulting (LDH/PANI){sub n} multilayer films possess high selectively response to ammonia at room temperature. The presence of LDH nanosheets plays a critical role on the gas sensing for the pure PANI film has very low response to ammonia. The LBL assembly process based on LDH combines the conducting polymer and nano-inorganic material, which provides opportunities to develop new inorganic–organic films for gas sensing.

  16. Capacitive Structures for Gas and Biological Sensing

    KAUST Repository

    Sapsanis, Christos

    2015-04-01

    The semiconductor industry was benefited by the advances in technology in the last decades. This fact has an impact on the sensors field, where the simple transducer was evolved into smart miniaturized multi-functional microsystems. However, commercially available gas and biological sensors are mostly bulky, expensive, and power-hungry, which act as obstacles to mass use. The aim of this work is gas and biological sensing using capacitive structures. Capacitive sensors were selected due to its design simplicity, low fabrication cost, and no DC power consumption. In the first part, the dominant structure among interdigitated electrodes (IDEs), fractal curves (Peano and Hilbert) and Archimedean spiral was investigated from capacitance density perspective. The investigation consists of geometrical formula calculations, COMSOL Multiphysics simulations and cleanroom fabrication of the capacitors on a silicon substrate. Moreover, low-cost fabrication on flexible plastic PET substrate was conducted outside cleanroom with rapid prototyping using a maskless laser etching. The second part contains the humidity, Volatile Organic compounds (VOCs) and Ammonia sensing of polymers, Polyimide and Nafion, and metal-organic framework (MOF), Cu(bdc)2.xH2O using IDEs and tested in an automated gas setup for experiment control and data extraction. The last part includes the biological sensing of C - reactive protein (CRP) quantification, which is considered as a biomarker of being prone to cardiac diseases and Bovine serum albumin (BSA) protein quantification, which is used as a reference for quantifying unknown proteins.

  17. Mitigating Greenhouse Gas and Ammonia Emissions from Swine Manure Management

    NARCIS (Netherlands)

    Wang, Yue; Dong, Hongmin; Zhu, Zhiping; Gerber, Pierre J.; Xin, Hongwei; Smith, Pete; Opio, Carolyn; Steinfeld, Henning; Chadwick, Dave

    2017-01-01

    Gaseous emissions from animal manure are considerable contributor to global ammonia (NH3) and agriculture greenhouse gas (GHG) emissions. Given the demand to promote mitigation of GHGs while fostering sustainable development of the Paris Agreement, an improvement of management systems

  18. Effect of CSA Concentration on the Ammonia Sensing Properties of CSA-Doped PA6/PANI Composite Nanofibers

    Directory of Open Access Journals (Sweden)

    Zengyuan Pang

    2014-11-01

    Full Text Available Camphor sulfonic acid (CSA-doped polyamide 6/polyaniline (PA6/PANI composite nanofibers were fabricated using in situ polymerization of aniline under different CSA concentrations (0.02, 0.04, 0.06, 0.08 and 0.10 M with electrospun PA6 nanofibers as templates. The structural, morphological and ammonia sensing properties of the prepared composite nanofibers were studied using scanning electron microscopy (SEM, Fourier transform infrared spectroscopy (FT-IR, four-point probe techniques, X-ray diffraction (XRD and a home-made gas sensing test system. All the results indicated that the CSA concentration had a great influence on the sensing properties of CSA-doped PA6/PANI composite nanofibers. The composite nanofibers doped with 0.02 M CSA showed the best ammonia sensing properties, with a significant sensitivity toward ammonia (NH3 at room temperature, superior to that of the composite nanofibers doped with 0.04–0.10 mol/L CSA. It was found that for high concentrations of CSA, the number of PANI–H+ reacted with NH3 would not make up a high proportion of all PANI–H+ within certain limits. As a result, within a certain range even though higher CSA-doped PA6/PANI nanofibers had better conductivity, their ammonia sensing performance would degrade.

  19. Nanostructured ZnO Films for Room Temperature Ammonia Sensing

    Science.gov (United States)

    Dhivya Ponnusamy; Sridharan Madanagurusamy

    2014-09-01

    Zinc oxide (ZnO) thin films have been deposited by a reactive dc magnetron sputtering technique onto a thoroughly cleaned glass substrate at room temperature. X-ray diffraction revealed that the deposited film was polycrystalline in nature. The field emission scanning electron micrograph (FE-SEM) showed the uniform formation of a rugby ball-shaped ZnO nanostructure. Energy dispersive x-ray analysis (EDX) confirmed that the film was stoichiometric and the direct band gap of the film, determined using UV-Vis spectroscopy, was 3.29 eV. The ZnO nanostructured film exhibited better sensing towards ammonia (NH3) at room temperature (˜30°C). The fabricated ZnO film based sensor was capable of detecting NH3 at as low as 5 ppm, and its parameters, such as response, selectivity, stability, and response/recovery time, were also investigated.

  20. Multilayer films of layered double hydroxide/polyaniline and their ammonia sensing behavior.

    Science.gov (United States)

    Xu, Dong-Mei; Guan, Mei-Yu; Xu, Qing-Hong; Guo, Ying

    2013-11-15

    This paper reports the fabrication of layered double hydroxide (LDH)/conductive polymer multilayer films by alternate assembly of exfoliated ZnAl-LDH nanosheets and polyaniline (PANI) on silicon wafer substrates using the layer-by-layer (LBL) deposition technology. UV-vis absorption spectroscopy indicates a stepwise and regular growth of the (LDH/PANI)n multilayer films upon increasing deposition cycles. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrate that the surfaces of the films are microscopy smooth and uniform with a thickness of 2 nm per bilayer. Furthermore, the resulting (LDH/PANI)n multilayer films possess high selectively response to ammonia at room temperature. The presence of LDH nanosheets plays a critical role on the gas sensing for the pure PANI film has very low response to ammonia. The LBL assembly process based on LDH combines the conducting polymer and nano-inorganic material, which provides opportunities to develop new inorganic-organic films for gas sensing.

  1. Decoration of vertical graphene with aerosol nanoparticles for gas sensing

    Science.gov (United States)

    Cui, Shumao; Guo, Xiaoru; Ren, Ren; Zhou, Guihua; Chen, Junhong

    2015-08-01

    A facile method was demonstrated to decorate aerosol Ag nanoparticles onto vertical graphene surfaces using a mini-arc plasma reactor. The vertical graphene was directly grown on a sensor electrode using a plasma-enhanced chemical vapor deposition (PECVD) method. The aerosol Ag nanoparticles were synthesized by a simple vapor condensation process using a mini-arc plasma source. Then, the nanoparticles were assembled on the surface of vertical graphene through the assistance of an electric field. Based on our observation, nonagglomerated Ag nanoparticles formed in the gas phase and were assembled onto vertical graphene sheets. Nanohybrids of Ag nanoparticle-decorated vertical graphene were characterized for ammonia gas detection at room temperature. The vertical graphene served as the conductance channel, and the conductance change upon exposure to ammonia was used as the sensing signal. The sensing results show that Ag nanoparticles significantly improve the sensitivity, response time, and recovery time of the sensor.

  2. Palladium Decorated Graphene-Nanoribbon Network for Enhanced Gas Sensing.

    Science.gov (United States)

    Kuru, Cihan; Choi, Duyoung; Choi, Chulmin; Kim, Young Jin; Jin, Sungho

    2015-03-01

    The fabrication of large-scale graphene nanoribbon (GNR) network and its application for gas sensing are reported. A large area, nanoscale GNR network was produced by a facile approach of silver nanowires (Ag NWs) templated graphene masking and subsequent 02 plasma etching. GNR network shows significantly enhanced sensitivity to ammonia gas compared to pristine graphene layer. The gas detection sensitivity of the nanoscale GNR network is even further improved by decorating GNR network with palladium (Pd) or platinum (Pt) nanoparticles, which show a relative resistance response of 65% and 45%, respectively to 50 ppm (parts per million) of ammonia (NH3) in nitrogen (N2) at room temperature as well as good reversibility in air.

  3. Gas Turbine Combustion and Ammonia Removal Technology of Gasified Fuels

    Directory of Open Access Journals (Sweden)

    Takeharu Hasegawa

    2010-03-01

    Full Text Available From the viewpoints of securing a stable supply of energy and protecting our global environment in the future, the integrated gasification combined cycle (IGCC power generation of various gasifying methods has been introduced in the world. Gasified fuels are chiefly characterized by the gasifying agents and the synthetic gas cleanup methods and can be divided into four types. The calorific value of the gasified fuel varies according to the gasifying agents and feedstocks of various resources, and ammonia originating from nitrogenous compounds in the feedstocks depends on the synthetic gas clean-up methods. In particular, air-blown gasified fuels provide low calorific fuel of 4 MJ/m3 and it is necessary to stabilize combustion. In contrast, the flame temperature of oxygen-blown gasified fuel of medium calorie between approximately 9–13 MJ/m3 is much higher, so control of thermal-NOx emissions is necessary. Moreover, to improve the thermal efficiency of IGCC, hot/dry type synthetic gas clean-up is needed. However, ammonia in the fuel is not removed and is supplied into the gas turbine where fuel-NOx is formed in the combustor. For these reasons, suitable combustion technology for each gasified fuel is important. This paper outlines combustion technologies and combustor designs of the high temperature gas turbine for various IGCCs. Additionally, this paper confirms that further decreases in fuel-NOx emissions can be achieved by removing ammonia from gasified fuels through the application of selective, non-catalytic denitration. From these basic considerations, the performance of specifically designed combustors for each IGCC proved the proposed methods to be sufficiently effective. The combustors were able to achieve strong results, decreasing thermal-NOx emissions to 10 ppm (corrected at 16% oxygen or less, and fuel-NOx emissions by 60% or more, under conditions where ammonia concentration per fuel heating value in unit volume was 2.4 × 102 ppm

  4. Understanding Gas-Phase Ammonia Chemistry in Protoplanetary Disks

    Science.gov (United States)

    Chambers, Lauren; Oberg, Karin I.; Cleeves, Lauren Ilsedore

    2017-01-01

    Protoplanetary disks are dynamic regions of gas and dust around young stars, the remnants of star formation, that evolve and coagulate over millions of years in order to ultimately form planets. The chemical composition of protoplanetary disks is affected by both the chemical and physical conditions in which they develop, including the initial molecular abundances in the birth cloud, the spectrum and intensity of radiation from the host star and nearby systems, and mixing and turbulence within the disk. A more complete understanding of the chemical evolution of disks enables a more complete understanding of the chemical composition of planets that may form within them, and of their capability to support life. One element known to be essential for life on Earth is nitrogen, which often is present in the form of ammonia (NH3). Recent observations by Salinas et al. (2016) reveal a theoretical discrepancy in the gas-phase and ice-phase ammonia abundances in protoplanetary disks; while observations of comets and protostars estimate the ice-phase NH3/H2O ratio in disks to be 5%, Salinas reports a gas-phase NH3/H2O ratio of ~7-84% in the disk surrounding TW Hydra, a young nearby star. Through computational chemical modeling of the TW Hydra disk using a reaction network of over 5000 chemical reactions, I am investigating the possible sources of excess gas-phase NH3 by determining the primary reaction pathways of NH3 production; the downstream chemical effects of ionization by ultraviolet photons, X-rays, and cosmic rays; and the effects of altering the initial abundances of key molecules such as N and N2. Beyond providing a theoretical explanation for the NH3 ice/gas discrepancy, this new model may lead to fuller understanding of the gas-phase formation processes of all nitrogen hydrides (NHx), and thus fuller understanding of the nitrogen-bearing molecules that are fundamental for life as we know it.

  5. Ammonia vapor sensing properties of polyaniline-titanium(IV)phosphate cation exchange nanocomposite.

    Science.gov (United States)

    Khan, Asif Ali; Baig, Umair; Khalid, Mohd

    2011-02-28

    In this study, the electrically conducting polyaniline-titanium(IV)phosphate (PANI-TiP) cation exchange nanocomposite was synthesized by sol-gel method. The cation exchange nanocomposite based sensor for detection of ammonia vapors was developed at room temperature. It was revealed that the sensor showed good reversible response towards ammonia vapors ranging from 3 to 6%. It was found that the sensor with p-toluene sulphonic acid (p-TSA) doped exhibited higher sensing response than hydrochloric acid doped. This sensor has detection limit ≤1% ammonia. The response of resistivity changes of the cation exchange nanocomposite on exposure to different concentrations of ammonia vapors shows its utility as a sensing material. These studies suggest that the cation exchange nanocomposite could be a good material for ammonia sensor at room temperature.

  6. Catalysts for selective oxidation of ammonia in a gas containing hydrogen

    DEFF Research Database (Denmark)

    2014-01-01

    The invention contributes to a cost effective way to solve the problem of trace ammonia removal from hydrogen containing gas. The set of catalysts of the invention selectively oxidised ammonia in ppm concentration even in gas mixture containing hydrogen gas in concentration of three orders...

  7. Catalysts for selective oxidation of ammonia in a gas containing hydrogen

    DEFF Research Database (Denmark)

    2015-01-01

    The invention contributes to a cost effective way to solve the problem of trace ammonia removal from a hydrogen and nitrogen containing gas. The set of catalysts of the invention selectively oxidised ammonia in ppm concentration even in gas mixtures containing hydrogen gas in concentrations...

  8. Experimental study of separation of ammonia synthesis vent gas by hydrate formation

    Institute of Scientific and Technical Information of China (English)

    Dong Taibin; Wang Leiyan; Liu Aixian; Guo Xuqiang; Ma Qinglan; Li Guowen; Sun Qiang

    2009-01-01

    Termodynamic data on methane hydrate formation in the presence of ammonia are very important for upgrading of ammonia synthesis vent gas using hydrate formation.This paper is focused on the formation conditions of methane hydrate in the presence of ammonia and the effects of gas-liquid ratio and temperature on the separation of vent gas by hydrate formation.Equilibrium data for methane hydrate within an ammonia mole concentration range from 1% to 5 % were obtained.The experimental results indicated that ammonia has an inhibitive effect on hydrate formation.The higher the ammonia concentration, the higher is the pressure reguired for methane hydrate formation would be.The primary experimental results showed that when volume ratio of gas to liquid was 80:1 and temperature was 283.15 K, total mole fraction of (H2+N2) in gas phase could reach 96.9 %.

  9. Magnetron sputtered nanostructured cadmium oxide films for ammonia sensing

    Energy Technology Data Exchange (ETDEWEB)

    Dhivya, P. [Functional Nanomaterials and Devices Lab, Centre for Nanotechnology and Advanced Biomaterials and School of Electrical and Electronics Engineering, SASTRA University, Thanjavur-613 401 (India); Prasad, A.K. [Surface and Nanoscience Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102 (India); Sridharan, M., E-mail: m.sridharan@ece.sastra.edu [Functional Nanomaterials and Devices Lab, Centre for Nanotechnology and Advanced Biomaterials and School of Electrical and Electronics Engineering, SASTRA University, Thanjavur-613 401 (India)

    2014-06-01

    Nanostructured cadmium oxide (CdO) films were deposited on to glass substrates by reactive dc magnetron sputtering technique. The depositions were carried out for different deposition times in order to obtain films with varying thicknesses. The CdO films were polycrystalline in nature with cubic structure showing preferred orientation in (1 1 1) direction as observed by X-ray diffraction (XRD). Field-emission scanning electron microscope (FE-SEM) micrographs showed uniform distribution of grains of 30–35 nm size and change in morphology from spherical to elliptical structures upon increasing the film thickness. The optical band gap value of the CdO films decreased from 2.67 to 2.36 eV with increase in the thickness. CdO films were deposited on to interdigitated electrodes to be employed as ammonia (NH{sub 3}) gas sensor. The fabricated CdO sensor with thickness of 294 nm has a capacity to detect NH{sub 3} as low as 50 ppm at a relatively low operating temperature of 150 °C with quick response and recovery time. - Highlights: • Nanostructured CdO films were deposited on to glass substrates using magnetron sputtering. • Deposition time was varied in order to obtain films with different thicknesses. • The CdO films were polycrystalline in nature with preferred orientation along (1 1 1) direction. • The optical bandgap values of the films decreased on increasing the thickness of the films. • CdO films with different thickness such as 122, 204, 294 nm was capable to detect NH{sub 3} down to 50 ppm at operating temperature of 150 °C.

  10. A Survey on Gas Sensing Technology

    Directory of Open Access Journals (Sweden)

    Huansheng Ning

    2012-07-01

    Full Text Available Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different scenarios with enhanced gas sensor calibration. This paper reviews the descriptions, evaluation, comparison and recent developments in existing gas sensing technologies. A classification of sensing technologies is given, based on the variation of electrical and other properties. Detailed introduction to sensing methods based on electrical variation is discussed through further classification according to sensing materials, including metal oxide semiconductors, polymers, carbon nanotubes, and moisture absorbing materials. Methods based on other kinds of variations such as optical, calorimetric, acoustic and gas-chromatographic, are presented in a general way. Several suggestions related to future development are also discussed. Furthermore, this paper focuses on sensitivity and selectivity for performance indicators to compare different sensing technologies, analyzes the factors that influence these two indicators, and lists several corresponding improved approaches.

  11. Sampling small volumes of ambient ammonia using a miniaturized gas sampler

    NARCIS (Netherlands)

    Timmer, B.H.; Olthuis, Wouter; van den Berg, Albert

    2004-01-01

    The development of a gas sampler for a miniaturized ambient ammonia detector is described. A micromachined channel system is realized in glass and silicon using powder blasting and anodic bonding. The analyte gas is directly mixed with purified water, dissolving the ammonia that will dissociate into

  12. A Survey on Gas Sensing Technology

    CERN Document Server

    Liu, Xiao; Liu, Hong; Hu, Sha; Zhang, Daqiang; Ning, Huansheng

    2013-01-01

    Sensing technology has been widely investigated and utilized for gas detection. Due to the different applicability and inherent limitations of different gas sensing technologies, researchers have been working on different scenarios with enhanced gas sensor calibration. This paper reviews the descriptions, evaluation, comparison and recent developments in existing gas sensing technologies. A classification of sensing technologies is given, based on the variation of electrical and other properties. Detailed introduction to sensing methods based on electrical variation is discussed through further classification according to sensing materials, including metal oxide semiconductors, polymers, carbon nanotubes, and moisture absorbing materials. Methods based on other kinds of variations such as optical, calorimetric, acoustic and gas-chromatographic, are presented in a general way. Several suggestions related to future development are also discussed. Furthermore, this paper focuses on sensitivity and selectivity fo...

  13. Graphene Hybrid Materials in Gas Sensing Applications

    Directory of Open Access Journals (Sweden)

    Usman Latif

    2015-12-01

    Full Text Available Graphene, a two dimensional structure of carbon atoms, has been widely used as a material for gas sensing applications because of its large surface area, excellent conductivity, and ease of functionalization. This article reviews the most recent advances in graphene hybrid materials developed for gas sensing applications. In this review, synthetic approaches to fabricate graphene sensors, the nano structures of hybrid materials, and their sensing mechanism are presented. Future perspectives of this rapidly growing field are also discussed.

  14. Metal oxide nanostructures as gas sensing devices

    CERN Document Server

    Eranna, G

    2011-01-01

    Metal Oxide Nanostructures as Gas Sensing Devices explores the development of an integrated micro gas sensor that is based on advanced metal oxide nanostructures and is compatible with modern semiconductor fabrication technology. This sensor can then be used to create a compact, low-power, handheld device for analyzing air ambience. The book first covers current gas sensing tools and discusses the necessity for miniaturized sensors. It then focuses on the materials, devices, and techniques used for gas sensing applications, such as resistance and capacitance variations. The author addresses th

  15. Fabrication of interdigitated electrodes by inkjet printing technology for apllication in ammonia sensing

    Science.gov (United States)

    Dam Le, Duy; Nhien Nguyen, Thi Ngoc; Chanh Tin Doan, Duc; Dung Dang, Thi My; Chien Dang, Mau

    2016-06-01

    In this paper interdigitated electrodes for gas sensors were fabricated by inkjet printing technology. Silver electrodes were inkjet printed on Si/SiO2 substrates instead of traditional photolithography method. The inkjet printing parameters to obtain desired dimensions, thickness of the electrodes and distance between the interdigitated electrodes were optimized in this study. The fabricated interdigitated silver electrodes were tested for application in ammonia gas sensors. Conductive polyaniline (PANI) layer was coated on the silver interdigitated electrodes by drop-coating. Ammonia detection of the PANI-coated chips was characterized with a gas measurement system in which humidity and ammonia concentrations were well-controlled. The electrical conductivity of the PANI films coated on the electrodes was measured when the PANI films were exposed to nitrogen and ammonia. The conductivity of the PANI films decreased significantly due to the deprotonation process of PANI upon ammonia expodure. The recovery time was about 15 min by heating up the polymer chip at 60 °C. The results showed that the silver electrodes fabricated by inkjet printing technique could be used as a sensor platform for ammonia detection.

  16. A study on reduced chemical mechanisms of ammonia/methane combustion under gas turbine conditions

    OpenAIRE

    Xiao, Hua; Howard, Michael; Valera Medina, Agustin; Dooley, Stephen; Bowen, Philip John

    2016-01-01

    As an alternative fuel and hydrogen carrier, ammonia is believed to have good potential for future power generation. To explore the feasibility of co-firing ammonia with methane, studies involving robust numerical analyses with detailed chemistry are required to progress towards industrial implementation. Therefore, the objective of this study is to determine a reduced mechanism for simulation studies of ammonia/methane combustion in practical gas turbine combustor conditions. Firstly, five d...

  17. Catalytic decomposition of ammonia in a fuel gas at high temperature and pressure

    Energy Technology Data Exchange (ETDEWEB)

    Mojtahedi, W.; Abbasian, J. [Enviropower Inc., Espoo (Finland)

    1995-11-01

    In connection with the purification of fuel gas for gas turbines in the IGCC process to meet NO{sub x} standards and maintain the thermal efficiency of the process, tests were carried out with a 7.5 cm pressurized reactor to decompose ammonia at high temperature (700-900{degree}C) and pressure (2 MPa) using Ni-based catalysts. The effects of temperature, pressure, ammonia concentration and gas residence time were determined. The simulated coal gas composition was varied to allow assessment of the effect of contaminants (sulfur compounds and tars) on the ammonia decomposition efficiency of five catalysts under otherwise identical operating conditions. The results show that two of the catalysts tested are capable of efficiently reducing the concentration of ammonia in the gas. 12 refs., 13 figs.

  18. Recovery of ammonia from swine manure using gas-permeable membranes: Effect of aeration

    Science.gov (United States)

    Gas-permeable membranes can recover ammonia from manure, reducing pollution whilst converting ammonia into ammonium salt fertilizer. The process involves manure pH control to increase ammonium (NH4) recovery rate that is normally carried out using an alkali. In this study a new strategy to avoid the...

  19. Improved recovery of ammonia from swine manure using gas-permeable membrane technology and aeration

    Science.gov (United States)

    Significant efforts are required to abate ammonia emissions from livestock operations. In addition, the costs of fertilizers have rapidly increased in recent years, especially nitrogen fertilizer such as anhydrous ammonia which is made from natural gas. Thus, new technologies for abatement of ammoni...

  20. Enhancing recovery of ammonia from swine manure anaerobic digester effluent using gas-permeable membrane technology

    Science.gov (United States)

    Gas-permeable membrane technology is useful to recover ammonia from manure. In this study, the technology was enhanced using aeration instead of alkali chemicals to increase pH and the ammonia recovery rate. Digested effluents from covered anaerobic swine lagoons containing 1375 to 2089 milligram am...

  1. Removal and recovery of ammonia from livestock wastewater using hydrophobic gas-permeable membranes

    Science.gov (United States)

    The costs of fertilizers have rapidly increased in recent years, especially nitrogen fertilizer such as anhydrous ammonia which is made from natural gas. Thus, new treatment technologies for abatement of ammonia emissions in livestock operations are being focused on nitrogern (N) recovery in additio...

  2. High-Performance Wireless Ammonia Gas Sensors Based on Reduced Graphene Oxide and Nano-Silver Ink Hybrid Material Loaded on a Patch Antenna.

    Science.gov (United States)

    Wu, Bian; Zhang, Xingfei; Huang, Beiju; Zhao, Yutong; Cheng, Chuantong; Chen, Hongda

    2017-09-09

    Reduced graphene oxide (rGO) has been studied as a resistive ammonia gas sensor at room temperature. The sensitive hybrid material composed of rGO and nano-silver ink (Ag-ink) was loaded on a microstrip patch antenna to realize high-performance wireless ammonia sensors. The material was investigated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Firstly, interdigital electrodes (IDEs) printed on the polyethylene terephthalate (PET) by direct printing were employed to measure the variation of resistance of the sensitive material with the ammonia concentration. The results indicated the response of sensor varied from 4.25% to 14.7% under 15-200 ppm ammonia concentrations. Furthermore, the hybrid material was loaded on a microstrip patch antenna fabricated by a conventional printed circuit board (PCB) process, and a 10 MHz frequency shift of the sensor antenna could be observed for 200 ppm ammonia gas. Finally, the wireless sensing property of the sensor antenna was successfully tested using the same emitted antenna outside the gas chamber with a high gain of 5.48 dBi, and an increased reflection magnitude of the emitted antenna due to the frequency mismatch of the sensor antenna was observed. Therefore, wireless ammonia gas sensors loaded on a patch antenna have significant application prospects in the field of Internet of Things (IoTs).

  3. Effect of Ni7+ Ion Irradiation on Structure and Ammonia Sensing Properties of Thermally Oxidized Zinc and Indium Films

    Institute of Scientific and Technical Information of China (English)

    Amandeep Kaur Bal; Rafinder Singh; R.K. Bedi

    2012-01-01

    ZnO and In203 films were prepared by thermal oxidation of vacuum deposited zinc and indium films, respec- tively onto the glass substrate at 30 ℃. The fabricated films have been irradiated with 100-MeV Ni7+ ions at different fluences ranging from 5×1011 to 5×1013 ions/cm2. The structural and gas sensing properties of pristine and irradiated films have been discussed. X-ray diffraction (XRD) pattern of pristine and irradiated films reveal that the films are polycrystalline in nature and crystallinity increases after irradiation. In this study, highly porous In203 nanorods evolved when being irradiated at a fluence of 5×1013 ions/cm2 while ZnO film shows decrease in number of nanowires. The ammonia sensing performance of the Ni^7+ irradiated In203 films shows an improvement as compared to its pristine counterpart.

  4. Methanol Gas-Sensing Properties of SWCNT-MIP Composites

    Science.gov (United States)

    Zhang, Jin; Zhu, Qin; Zhang, Yumin; Zhu, Zhongqi; Liu, Qingju

    2016-11-01

    The single-walled carbon nanotube (SWCNT)-molecularly imprinted powder (MIP) composites in this paper were prepared by mixing SWCNTs with MIPs. The structure and micrograph of the as-prepared SWCNTs-MIPs samples were characterized by XRD and TEM. The gas-sensing properties were tested through indirect-heating sensors based on SWCNT-MIP composites fabricating on an alumina tube with Au electrodes and Pt wires. The results showed that the structure of SWCNTs-MIPs is of orthogonal perovskite and the average particle size of the SWCNTs-MIPs was in the range of 10-30 nm. SWCNTs-MIPs exhibit good methanol gas-sensitive properties. At 90 °C, the response to 1 ppm methanol is 19.7, and the response to the interferent is lower than 5 to the other interferent gases (ethanol, formaldehyde, toluene, acetone, ammonia, and gasoline). The response time and recovery time are 50 and 58 s, respectively.

  5. Gas sensing in 2D materials

    Science.gov (United States)

    Yang, Shengxue; Jiang, Chengbao; Wei, Su-huai

    2017-06-01

    Two-dimensional (2D) layered inorganic nanomaterials have attracted huge attention due to their unique electronic structures, as well as extraordinary physical and chemical properties for use in electronics, optoelectronics, spintronics, catalysts, energy generation and storage, and chemical sensors. Graphene and related layered inorganic analogues have shown great potential for gas-sensing applications because of their large specific surface areas and strong surface activities. This review aims to discuss the latest advancements in the 2D layered inorganic materials for gas sensors. We first elaborate the gas-sensing mechanisms and introduce various types of gas-sensing devices. Then, we describe the basic parameters and influence factors of the gas sensors to further enhance their performance. Moreover, we systematically present the current gas-sensing applications based on graphene, graphene oxide (GO), reduced graphene oxide (rGO), functionalized GO or rGO, transition metal dichalcogenides, layered III-VI semiconductors, layered metal oxides, phosphorene, hexagonal boron nitride, etc. Finally, we conclude the future prospects of these layered inorganic materials in gas-sensing applications.

  6. A Portable Array-Type Optical Fiber Sensing Instrument for Real-Time Gas Detection

    Directory of Open Access Journals (Sweden)

    San-Shan Hung

    2016-12-01

    Full Text Available A novel optical fiber array-type of sensing instrument with temperature compensation for real-time detection was developed to measure oxygen, carbon dioxide, and ammonia simultaneously. The proposed instrument is multi-sensing array integrated with real-time measurement module for portable applications. The sensing optical fibers were etched and polished before coating to increase sensitivities. The ammonia and temperature sensors were each composed of a dye-coated single-mode fiber with constructing a fiber Bragg grating and a long-period filter grating for detecting light intensity. Both carbon dioxide and oxygen sensing structures use multimode fibers where 1-hydroxy-3,6,8-pyrene trisulfonic acid trisodium salt is coated for carbon dioxide sensing and Tris(2,2′-bipyridyl dichlororuthenium(II hexahydrate and Tris(bipyridineruthenium(II chloride are coated for oxygen sensing. Gas-induced fluorescent light intensity variation was applied to detect gas concentration. The portable gas sensing array was set up by integrating with photo-electronic measurement modules and a human-machine interface to detect gases in real time. The measured data have been processed using piecewise-linear method. The sensitivity of the oxygen sensor were 1.54%/V and 9.62%/V for concentrations less than 1.5% and for concentrations between 1.5% and 6%, respectively. The sensitivity of the carbon dioxide sensor were 8.33%/V and 9.62%/V for concentrations less than 2% and for concentrations between 2% and 5%, respectively. For the ammonia sensor, the sensitivity was 27.78%/V, while ammonia concentration was less than 2%.

  7. A Portable Array-Type Optical Fiber Sensing Instrument for Real-Time Gas Detection.

    Science.gov (United States)

    Hung, San-Shan; Chang, Hsing-Cheng; Chang, I-Nan

    2016-12-08

    A novel optical fiber array-type of sensing instrument with temperature compensation for real-time detection was developed to measure oxygen, carbon dioxide, and ammonia simultaneously. The proposed instrument is multi-sensing array integrated with real-time measurement module for portable applications. The sensing optical fibers were etched and polished before coating to increase sensitivities. The ammonia and temperature sensors were each composed of a dye-coated single-mode fiber with constructing a fiber Bragg grating and a long-period filter grating for detecting light intensity. Both carbon dioxide and oxygen sensing structures use multimode fibers where 1-hydroxy-3,6,8-pyrene trisulfonic acid trisodium salt is coated for carbon dioxide sensing and Tris(2,2'-bipyridyl) dichlororuthenium(II) hexahydrate and Tris(bipyridine)ruthenium(II) chloride are coated for oxygen sensing. Gas-induced fluorescent light intensity variation was applied to detect gas concentration. The portable gas sensing array was set up by integrating with photo-electronic measurement modules and a human-machine interface to detect gases in real time. The measured data have been processed using piecewise-linear method. The sensitivity of the oxygen sensor were 1.54%/V and 9.62%/V for concentrations less than 1.5% and for concentrations between 1.5% and 6%, respectively. The sensitivity of the carbon dioxide sensor were 8.33%/V and 9.62%/V for concentrations less than 2% and for concentrations between 2% and 5%, respectively. For the ammonia sensor, the sensitivity was 27.78%/V, while ammonia concentration was less than 2%.

  8. Gas Sensing Performance of Pure and Modified BST Thick Film Resistor

    Directory of Open Access Journals (Sweden)

    G. H. JAIN

    2008-04-01

    Full Text Available Barium Strontium Titanate (BST-(Ba0.87Sr0.13TiO3 ceramic powder was prepared by mechanochemical process. The thick films of different thicknesses of BST were prepared by screen-printing technique and gas-sensing performance of these films was tested for various gases. The films showed highest response and selectivity to ammonia gas. The pure BST film was surface modified by surfactant CrO3 by using dipping technique. The surface modified film suppresses the response to ammonia and enhances to H2S gas. The surface modification of films changes the adsorption-desorption relationship with the target gas and shifts its selectivity. The gas response, selectivity, response and recovery time of the pure and modified films were measured and presented.

  9. Ultrathin Gas Permeable Oxide Membranes for Chemical Sensing: Nanoporous Ta2O5 Test Study

    Directory of Open Access Journals (Sweden)

    Alexander Imbault

    2015-09-01

    Full Text Available Conductometric gas sensors made of gas permeable metal oxide ultrathin membranes can combine the functions of a selective filter, preconcentrator, and sensing element and thus can be particularly promising for the active sampling of diluted analytes. Here we report a case study of the electron transport and gas sensing properties of such a membrane made of nanoporous Ta2O5. These membranes demonstrated a noticeable chemical sensitivity toward ammonia, ethanol, and acetone at high temperatures above 400 °C. Different from traditional thin films, such gas permeable, ultrathin gas sensing elements can be made suspended enabling advanced architectures of ultrasensitive analytical systems operating at high temperatures and in harsh environments.

  10. AMMONIA REMOVAL AND NITROUS OXIDE PRODUCTION IN GAS-PHASE COMPOST BIOFILTERS

    Science.gov (United States)

    Biofiltration technology is widely utilized for treating ammonia gas (NH3), with one of its potential detrimental by-products being nitrous oxide (N2O), a greenhouse gas approximately 300 times more reactive to infrared than CO2. The present work intends to provide the relation between NH3 removal d...

  11. Manufacture of a Polyaniline Nanofiber Ammonia Sensor Integrated with a Readout Circuit Using the CMOS-MEMS Technique

    Science.gov (United States)

    Liu, Mao-Chen; Dai, Ching-Liang; Chan, Chih-Hua; Wu, Chyan-Chyi

    2009-01-01

    This study presents the fabrication of a polyaniline nanofiber ammonia sensor integrated with a readout circuit on a chip using the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process. The micro ammonia sensor consists of a sensing resistor and an ammonia sensing film. Polyaniline prepared by a chemical polymerization method was adopted as the ammonia sensing film. The fabrication of the ammonia sensor needs a post-process to etch the sacrificial layers and to expose the sensing resistor, and then the ammonia sensing film is coated on the sensing resistor. The ammonia sensor, which is of resistive type, changes its resistance when the sensing film adsorbs or desorbs ammonia gas. A readout circuit is employed to convert the resistance of the ammonia sensor into the voltage output. Experimental results show that the sensitivity of the ammonia sensor is about 0.88 mV/ppm at room temperature. PMID:22399944

  12. Manufacture of a Polyaniline Nanofiber Ammonia Sensor Integrated with a Readout Circuit Using the CMOS-MEMS Technique

    Directory of Open Access Journals (Sweden)

    Chyan-Chyi Wu

    2009-02-01

    Full Text Available This study presents the fabrication of a polyaniline nanofiber ammonia sensor integrated with a readout circuit on a chip using the commercial 0.35 mm complementary metal oxide semiconductor (CMOS process and a post-process. The micro ammonia sensor consists of a sensing resistor and an ammonia sensing film. Polyaniline prepared by a chemical polymerization method was adopted as the ammonia sensing film. The fabrication of the ammonia sensor needs a post-process to etch the sacrificial layers and to expose the sensing resistor, and then the ammonia sensing film is coated on the sensing resistor. The ammonia sensor, which is of resistive type, changes its resistance when the sensing film adsorbs or desorbs ammonia gas. A readout circuit is employed to convert the resistance of the ammonia sensor into the voltage output. Experimental results show that the sensitivity of the ammonia sensor is about 0.88 mV/ppm at room temperature

  13. Nanocomposite thin films for optical gas sensing

    Science.gov (United States)

    Ohodnicki, Paul R; Brown, Thomas D

    2014-06-03

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

  14. Studies on gas sensing performance of pure and modified barium strontium titanate thick film resistors

    Indian Academy of Sciences (India)

    G H Jain; L A Patil; P P Patil; U P Mulik; K R Patil

    2007-02-01

    Barium strontium titanate ((Ba0.87Sr0.13)TiO3–BST) ceramic powder was prepared by mechanochemical process. The thick films of different thicknesses of BST were prepared by screen-printing technique and gas-sensing performance of these films was tested for various gases. The films showed highest response and selectivity to ammonia gas. The effect of film thickness on gas response was also studied. As prepared BST thick films were surface modified by dipping them into an aqueous solution of titanium chloride (TiCl3) for different intervals of time. Surface modification shifted response to H2S gas suppressing the responses to ammonia and other gases. The surface modification, using dipping process, altered the adsorbate–adsorbent interactions, which gave the unusual sensitivity and selectivity effect. Sensitivity, selectivity, thermal stability, response and recovery time of the sensor were measured and presented.

  15. Sampling small volumes of ambient ammonia using a miniaturized gas sampler.

    Science.gov (United States)

    Timmer, Björn; Olthuis, Wouter; van den Berg, Albert

    2004-06-01

    The development of a gas sampler for a miniaturized ambient ammonia detector is described. A micromachined channel system is realized in glass and silicon using powder blasting and anodic bonding. The analyte gas is directly mixed with purified water, dissolving the ammonia that will dissociate into ammonium ions. Carrier gas bubbles are subsequently removed from the liquid stream through a venting hole sealed with a microporous water repellent PTFE membrane. A flow restrictor is placed at the outlet of the sampler to create a small overpressure underneath the membrane, enabling the gas to leave through the membrane. Experiments with a gas flow of 1 ml min(-1), containing ammonia concentrations ranging from 9.4 ppm to 0.6 ppm in a nitrogen carrier flow have been carried out, at a water flow of 20 microl min(-1). The ammonium concentration in the sample solution is measured with an electrolyte conductivity detector. The measured values correspond with the concentration calculated from the initial ammonia concentration in the analyte gas, the fifty times concentration enhancement due to the gas-liquid volume difference and the theoretical dissociation equilibrium as a function of the resulting pH.

  16. Soft sensing for gas-lift wells

    NARCIS (Netherlands)

    Bloemen, H.H.J.; Belfroid, S.P.C.; Sturm, W.L.; Verhelst, F.J.P.C.M.G.

    2006-01-01

    This paper considers the use of extended Kalman filtering as a soft-sensing technique for gas lift wells. This technique is deployed for the estimation of dynamic variables that are not directly measured. Possible applications are the estimation of flow rates from surface and downhole pressure measu

  17. Nanostructure Sensing and Transmission of Gas Data

    Science.gov (United States)

    Li, Jing (Inventor)

    2011-01-01

    A system for receiving, analyzing and communicating results of sensing chemical and/or physical parameter values, using wireless transmission of the data. Presence or absence of one or more of a group of selected chemicals in a gas or vapor is determined, using suitably functionalized carbon nanostructures that are exposed to the gas. One or more physical parameter values, such as temperature, vapor pressure, relative humidity and distance from a reference location, are also sensed for the gas, using nanostructures and/or microstructures. All parameter values are transmitted wirelessly to a data processing site or to a control site, using an interleaving pattern for data received from different sensor groups, using I.E.E.E. 802.11 or 802.15 protocol, for example. Methods for estimating chemical concentration are discussed.

  18. Measurement of the orientation of buffer-gas-cooled, electrostatically-guided ammonia molecules

    Science.gov (United States)

    Steer, Edward W.; Petralia, Lorenzo S.; Western, Colin M.; Heazlewood, Brianna R.; Softley, Timothy P.

    2017-02-01

    The extent to which the spatial orientation of internally and translationally cold ammonia molecules can be controlled as molecules pass out of a quadrupole guide and through different electric field regions is examined. Ammonia molecules are collisionally cooled in a buffer gas cell, and are subsequently guided by a three-bend electrostatic quadrupole into a detection chamber. The orientation of ammonia molecules is probed using (2 + 1) resonance-enhanced multiphoton ionisation (REMPI), with the laser polarisation axis aligned both parallel and perpendicular to the time-of-flight axis. Even with the presence of a near-zero field region, the ammonia REMPI spectra indicate some retention of orientation. Monte Carlo simulations propagating the time-dependent Schrödinger equation in a full basis set including the hyperfine interaction enable the orientation of ammonia molecules to be calculated - with respect to both the local field direction and a space-fixed axis - as the molecules pass through different electric field regions. The simulations indicate that the orientation of ∼95% of ammonia molecules in JK =11 could be achieved with the application of a small bias voltage (17 V) to the mesh separating the quadrupole and detection regions. Following the recent combination of the buffer gas cell and quadrupole guide apparatus with a linear Paul ion trap, this result could enable one to examine the influence of molecular orientation on ion-molecule reaction dynamics and kinetics.

  19. Enhancement of Alkene Epoxidation Activity of Titanosilicates by Gas-Phase Ammonia Modification

    Institute of Scientific and Technical Information of China (English)

    张里艳; 徐乐; 孙晶晶; 蒋金刚; 刘月明; 吴海虹; 吴鹏

    2012-01-01

    Novel ammonia-treated titanosilicates have been prepared by heating the samples of Ti-MWW, TS-l and Ti-Beta under pure ammonia gas flow at 673 K for a period of time. The ammonia modification improved their catalytic performance in liquid-phase oxidations. Especially, the catalytic activities of ammonified Ti-MWW, N-Ti-MWW, were enhanced greatly in the epoxidation of 1-hexene with H2O2. The reason that the ammonia treat- ment played such an important role in post-modification of titanosilicate was investigated in details. In comparison to the parent Ti-MWW catalyst, N-Ti-MMW was more robust and produced less coke in oxidation reactions.

  20. Surface studies of gas sensing metal oxides.

    Science.gov (United States)

    Batzill, Matthias; Diebold, Ulrike

    2007-05-21

    The relation of surface science studies of single crystal metal oxides to gas sensing applications is reviewed. Most metal oxide gas sensors are used to detect oxidizing or reducing gases and therefore this article focuses on surface reduction processes and the interaction of oxygen with these surfaces. The systems that are discussed are: (i) the oxygen vacancy formation on the surface of the ion conductor CeO(2)(111); (ii) interaction of oxygen with TiO(2) (both adsorption processes and the incorporation of oxygen into the TiO(2)(110) lattice are discussed); (iii) the varying surface composition of SnO(2)(101) and its consequence for the adsorption of water; and (iv) Cu modified ZnO(0001)-Zn surfaces and its interaction with oxygen. These examples are chosen to give a comprehensive overview of surface science studies of different kinds of gas sensing materials and to illustrate the potential that surface science studies have to give fundamental insight into gas sensing phenomena.

  1. Viral-templated gold/polypyrrole nanopeapods for an ammonia gas sensor

    Science.gov (United States)

    Yan, Yiran; Zhang, Miluo; Moon, Chung Hee; Su, Heng-Chia; Myung, Nosang V.; Haberer, Elaine D.

    2016-08-01

    One-dimensional gold/polypyrrole (Au/PPy) nanopeapods were fabricated using a viral template: M13 bacteriophage. The genetically modified filamentous virus displayed gold-binding peptides along its length, allowing selective attachment of gold nanoparticles (Au NPs) under ambient conditions. A PPy shell was electropolymerized on the viral-templated Au NP chains forming nanopeapod structures. The PPy shell morphology and thickness were controlled through electrodeposition potential and time, resulting in an ultra-thin conductive polymer shell of 17.4 ± 3.3 nm. A post-electrodeposition acid treatment was used to modify the electrical properties of these hybrid materials. The electrical resistance of the nanopeapods was monitored at each assembly step. Chemiresistive ammonia (NH3) gas sensors were developed from networks of the hybrid Au/PPy nanostructures. Room temperature sensing performance was evaluated from 5 to 50 ppmv and a mixture of reversible and irreversible chemiresistive behavior was observed. A sensitivity of 0.30%/ppmv was found for NH3 concentrations of 10 ppmv or less, and a lowest detection limit (LDL) of 0.007 ppmv was calculated. Furthermore, acid-treated devices exhibited an enhanced sensitivity of 1.26%/ppmv within the same concentration range and a calculated LDL of 0.005 ppmv.

  2. Enhanced recovery of ammonia from swine manure anaerobic digester effluent using gas-permeable membranes and aeration

    Science.gov (United States)

    Atmospheric ammonia pollution from livestock wastes can be reduced using gas-permeable membrane technology by converting ammonia contained in the manure into ammonium salt for use in fertilizers. In this study, gas-permeable membrane technology was enhanced using aeration combined with nitrificatio...

  3. Tungsten sulfide nanoflakes. Synthesis by electrospinning and their gas sensing properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ke; Qin, Xiang; Deng, Da-Shen; Feng, Xu; Zhang, Chao [Chongqing Univ. of Technology, Chongqing (China). Dept. of Physics and Energy; Feng, Wen-Lin [Chongqing Univ. of Technology, Chongqing (China). Dept. of Physics and Energy; Chongqing Key Laboratory of Modern Photoelectric Detection Technology and Instrument, Chongqing (China).

    2017-07-01

    Tungsten sulfide (WS{sub 2}) nanoflakes were successfully prepared via electrospinning with polyvinylpyrrolidone (PVP) as organic solvent. In addition, Ag-deposited WS{sub 2} (Ag-WS{sub 2}) was obtained by chemical blending/calcination method. The structure and morphology of as-prepared materials were characterised by powder X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The XRD result shows that the prepared WS{sub 2} has a graphene-like structure with P{sub 63/mmc} space group symmetry. The SEM illuminates that the sensing samples have nanoflake appearance. Furthermore, heater-type gas sensors were fabricated based on WS{sub 2} and Ag-WS{sub 2} nanomaterials. The sensing responses of WS{sub 2} and Ag-WS{sub 2} on the ammonia (NH{sub 3}), ethanol (C{sub 2}H{sub 5}OH), and acetone (C{sub 3}H{sub 6}O) were investigated at about 220 C. The results indicate that gas sensor based on WS{sub 2} and Ag-WS{sub 2} nanoflakes has 60 ppm sensing threshold value for ammonia. One possible gas sensing mechanism of WS{sub 2} and Ag-WS{sub 2} gas sensors is surface control via charge transfer.

  4. Tungsten Sulfide Nanoflakes: Synthesis by Electrospinning and Their Gas Sensing Properties

    Science.gov (United States)

    Wang, Ke; Feng, Wen-Lin; Qin, Xiang; Deng, Da-Shen; Feng, Xu; Zhang, Chao

    2017-04-01

    Tungsten sulfide (WS2) nanoflakes were successfully prepared via electrospinning with polyvinylpyrrolidone (PVP) as organic solvent. In addition, Ag-deposited WS2 (Ag-WS2) was obtained by chemical blending/calcination method. The structure and morphology of as-prepared materials were characterised by powder X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The XRD result shows that the prepared WS2 has a graphene-like structure with P63/mmc space group symmetry. The SEM illuminates that the sensing samples have nanoflake appearance. Furthermore, heater-type gas sensors were fabricated based on WS2 and Ag-WS2 nanomaterials. The sensing responses of WS2 and Ag-WS2 on the ammonia (NH3), ethanol (C2H5OH), and acetone (C3H6O) were investigated at about 220°C. The results indicate that gas sensor based on WS2 and Ag-WS2 nanoflakes has 60 ppm sensing threshold value for ammonia. One possible gas sensing mechanism of WS2 and Ag-WS2 gas sensors is surface control via charge transfer.

  5. Gas Composition Sensing Using Carbon Nanotube Arrays

    Science.gov (United States)

    Li, Jing; Meyyappan, Meyya

    2012-01-01

    This innovation is a lightweight, small sensor for inert gases that consumes a relatively small amount of power and provides measurements that are as accurate as conventional approaches. The sensing approach is based on generating an electrical discharge and measuring the specific gas breakdown voltage associated with each gas present in a sample. An array of carbon nanotubes (CNTs) in a substrate is connected to a variable-pulse voltage source. The CNT tips are spaced appropriately from the second electrode maintained at a constant voltage. A sequence of voltage pulses is applied and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of the current-voltage characteristics. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas. The CNTs in the gas sensor have a sharp (low radius of curvature) tip; they are preferably multi-wall carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs), to generate high-strength electrical fields adjacent to the tips for breakdown of the gas components with lower voltage application and generation of high current. The sensor system can provide a high-sensitivity, low-power-consumption tool that is very specific for identification of one or more gas components. The sensor can be multiplexed to measure current from multiple CNT arrays for simultaneous detection of several gas components.

  6. Single Chip Sensing of Multiple Gas Flows

    CERN Document Server

    Bruschi, P; Piotto, M

    2008-01-01

    The fabrication and experimental characterization of a thermal flow meter, capable of detecting and measuring two independent gas flows with a single chip, is described. The device is based on a 4 x 4 mm2 silicon chip, where a series of differential micro-anemometers have been integrated together with standard electronic components by means of postprocessing techniques. The innovative aspect of the sensor is the use of a plastic adapter, thermally bonded to the chip, to convey the gas flow only to the areas where the sensors are located. The use of this inexpensive packaging procedure to include different sensing structures in distinct flow channels is demonstrated.

  7. Ammonia and greenhouse gas emissions from constructed wetlands treating swine wastewater

    Science.gov (United States)

    Ammonia and greenhouse gas emissions from marsh-pond-marsh constructed wetlands treating swine wastewater were measured with closed-chamber technique using a photoacoustic multigas analyzer. Theory behind the technique was discussed and the technique was demonstrated with actual field data. Nitrous ...

  8. Gas-permeable hydrophobic tubular membranes for ammonia recovery in bio-electrochemical systems

    NARCIS (Netherlands)

    Kuntke, P.; Zamora, P.; Saakes, M.; Buisman, C.J.N.; Hamelers, H.V.M.

    2016-01-01

    The application of a gas-permeable hydrophobic tubular membrane in bio-electrochemical systems enables efficient recovery of ammonia (NH3) from their cathode compartments. Due to a hydrogen evolution reaction at the cathode, no chemical addition was required to increase the pH for continuous NH3

  9. Effect and mechanism of coking residual ammonia water treating by flue gas

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The treatment of coking residual ammonia water has been a bigdifficult problem at home and abroad, and there is no breakthrough research achievement in the past. The invention patent "The method of treating all coking wastewater or treating coking residual ammonia water by flue gas" has been successfully used in Huaian Steel Works for high concentration and organic industry wastewater treatment. Not only can it realize the wastewater zero discharge, but also the wastewater treatment has an effect of de-sulfur and de-nitrogen for flue gas. So that the flue gas exhaustcan meet the requirement of emission standard. The mass transfer and heat transfer, fly ash absorption and coagulation, acid and alkali neutralization reaction, catalysis oxidation and reduction reaction in flue gas would be the major factors.

  10. SULFUR DIOXIDE AND AMMONIA GAS REDUCTION USING COCONUT CELLULOSE AND ACETYLATED CELLULOSE

    Directory of Open Access Journals (Sweden)

    SURJANI WONORAHARDJO

    2016-07-01

    Full Text Available Some adsorbent materials were employed to reduce ammonia and carbon dioxide gases. Cellulose materials from nata de coco and grated coconut meat were packed in a column to be used as gas adsorbent. The effect of surface modification of cellulose by acetylation in order to enhance the sorption ability and capacity was also studied. Another factor that was tested was the column length. The characteristics of cellulose materials were done by electron microscopy, infrared spectroscopy, and physical parameters such as water and ash contents as well as iodine sorption ability. The amount of ammonia and sulfur dioxide gases absorbed by the materials were analyzed by visible spectroscopy. The results showed that the cellulose material can be good adsorbent for basic gas like ammonia as well as acidic sulfur dioxide gases. Acetylation as a method of surface modification gave the proof of better sorption for both gases but was greater for ammonia. However, the column length gave greater impact in ammonia compared to sulfur dioxide. This study provides a better explanation of dynamics at surfaces, in the search for better adsorbents.

  11. Nanocrystalline Al Composites from Powder Milled under Ammonia Gas Flow

    Directory of Open Access Journals (Sweden)

    J. Cintas

    2014-01-01

    Full Text Available The production of high hardness and thermally stable nanocrystalline aluminium composites is described. Al powder was milled at room temperature in an ammonia flow for a period of less than 5 h. NH3 dissociation during milling provokes the absorption, at a high rate, of nitrogen into aluminium, hardening it by forming a solid solution. Controlled amounts of AlN and Al5O6N are formed during the subsequent sintering of milled powders for consolidation. The pinning action of these abundant dispersoids highly restrains aluminium grain growth during heating. The mean size of the Al grains remains below 45 nm and even after the milled powder is sintered at 650°C for 1 h.

  12. Surface Morphology Dependent Copper Sulphide Ammonia Gas Sensor Working at Room Temperature: Effect of SHI Irradiation

    Directory of Open Access Journals (Sweden)

    Ramphal Sharma

    2009-02-01

    Full Text Available We report the synthesis of copper sulphide (CuS nano-pillars on copper sulphide thin film surface by using swift heavy ion (SHI irradiation. Thin films of CuS are irradiated with 100 MeV gold ions at fluence varying from 1011 to 5 ´ 1012 ions/cm2. These nanostructures grown on the surface of copper sulphide has been used for the detection of ammonia gas at room temperature. The time dependent surface conductance measurements show the utility of copper sulphide for the detection of ammonia. It is observed that the response of the material is highly influenced by the irradiation fluence.

  13. Surface Morphology Dependent Copper Sulphide Ammonia Gas Sensor Working at Room Temperature: Effect of SHI Irradiation

    OpenAIRE

    Ramphal Sharma; Sagade, Abhay A.; J. C. Vyas; P. K. Nema; Anil Ghule; Sung-Hwan Han

    2009-01-01

    We report the synthesis of copper sulphide (CuS) nano-pillars on copper sulphide thin film surface by using swift heavy ion (SHI) irradiation. Thin films of CuS are irradiated with 100 MeV gold ions at fluence varying from 1011 to 5 ´ 1012 ions/cm2. These nanostructures grown on the surface of copper sulphide has been used for the detection of ammonia gas at room temperature. The time dependent surface conductance measurements show the utility of copper sulphide for the detection of ammonia. ...

  14. Efficient Total Nitrogen Removal in an Ammonia Gas Biofilter through High-Rate OLAND

    DEFF Research Database (Denmark)

    De Clippeleir, Haydée; Courtens, Emilie; Mosquera, Mariela

    2012-01-01

    .86 ± 0.04 kg N m–3 biofilter d–1 and an empty bed residence time of 14 s. After 45 days of operation a stable nitrogen removal rate of 0.67 ± 0.06 kg N m–3 biofilter d–1, an ammonia removal efficiency of 99%, a removal of 75–80% of the total nitrogen, and negligible NO/N2O productions were obtained......Ammonia gas is conventionally treated in nitrifying biofilters; however, addition of organic carbon to perform post-denitrification is required to obtain total nitrogen removal. Oxygen-limited autotrophic nitrification/denitrification (OLAND), applied in full-scale for wastewater treatment, can...... offer a cost-effective alternative for gas treatment. In this study, the OLAND application thus was broadened toward ammonia loaded gaseous streams. A down flow, oxygen-saturated biofilter (height of 1.5 m; diameter of 0.11 m) was fed with an ammonia gas stream (248 ± 10 ppmv) at a loading rate of 0...

  15. Ammonia sensors and their applications - a review

    NARCIS (Netherlands)

    Timmer, Björn; Olthuis, Wouter; Berg, van den Albert

    2005-01-01

    Many scientific papers have been written concerning gas sensors for different sensor applications using several sensing principles. This review focuses on sensors and sensor systems for gaseous ammonia. Apart from its natural origin, there are many sources of ammonia, like the chemical industry or i

  16. From the Solution Processing of Hydrophilic Molecules to Polymer-Phthalocyanine Hybrid Materials for Ammonia Sensing in High Humidity Atmospheres

    Science.gov (United States)

    Gaudillat, Pierre; Jurin, Florian; Lakard, Boris; Buron, Cédric; Suisse, Jean-Moïse; Bouvet, Marcel

    2014-01-01

    We have prepared different hybrid polymer-phthalocyanine materials by solution processing, starting from two sulfonated phthalocyanines, s-CoPc and CuTsPc, and polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), poly(acrylic acid-co-acrylamide) (PAA-AM), poly(diallyldimethylammonium chloride) (PDDA) and polyaniline (PANI) as polymers. We also studied the response to ammonia (NH3) of resistors prepared from these sensing materials. The solvent casted films, prepared from s-CoPc and PVP, PEG and PAA-AM, were highly insulating and very sensitive to the relative humidity (RH) variation. The incorporation of s-CoPc in PDDA by means of layer-by-layer (LBL) technique allowed to stabilize the film, but was too insulating to be interesting. We also prepared PANI-CuTsPc hybrid films by LBL technique. It allowed a regular deposition as evidenced by the linear increase of the absorbance at 688 nm as a function of the number of bilayers. The sensitivity to ammonia (NH3) of PANi-CuTsPc resistors was very high compared to that of individual materials, giving up to 80% of current decrease when exposed to 30 ppm NH3. Contrarily to what happens with neutral polymers, in PANI, CuTsPc was stabilized by strong electrostatic interactions, leading to a stable response to NH3, whatever the relative humidity in the range 10%–70%. Thus, the synergy of PANI with ionic macrocycles used as counteranions combined with their simple aqueous solution processing opens the way to the development of new gas sensors capable of operating in real world conditions. PMID:25061841

  17. From the solution processing of hydrophilic molecules to polymer-phthalocyanine hybrid materials for ammonia sensing in high humidity atmospheres.

    Science.gov (United States)

    Gaudillat, Pierre; Jurin, Florian; Lakard, Boris; Buron, Cédric; Suisse, Jean-Moïse; Bouvet, Marcel

    2014-07-24

    We have prepared different hybrid polymer-phthalocyanine materials by solution processing, starting from two sulfonated phthalocyanines, s-CoPc and CuTsPc, and polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), poly(acrylic acid-co-acrylamide) (PAA-AM), poly(diallyldimethylammonium chloride) (PDDA) and polyaniline (PANI) as polymers. We also studied the response to ammonia (NH3) of resistors prepared from these sensing materials. The solvent casted films, prepared from s-CoPc and PVP, PEG and PAA-AM, were highly insulating and very sensitive to the relative humidity (RH) variation. The incorporation of s-CoPc in PDDA by means of layer-by-layer (LBL) technique allowed to stabilize the film, but was too insulating to be interesting. We also prepared PANI-CuTsPc hybrid films by LBL technique. It allowed a regular deposition as evidenced by the linear increase of the absorbance at 688 nm as a function of the number of bilayers. The sensitivity to ammonia (NH3) of PANi-CuTsPc resistors was very high compared to that of individual materials, giving up to 80% of current decrease when exposed to 30 ppm NH3. Contrarily to what happens with neutral polymers, in PANI, CuTsPc was stabilized by strong electrostatic interactions, leading to a stable response to NH3, whatever the relative humidity in the range 10%-70%. Thus, the synergy of PANI with ionic macrocycles used as counteranions combined with their simple aqueous solution processing opens the way to the development of new gas sensors capable of operating in real world conditions.

  18. From the Solution Processing of Hydrophilic Molecules to Polymer-Phthalocyanine Hybrid Materials for Ammonia Sensing in High Humidity Atmospheres

    Directory of Open Access Journals (Sweden)

    Pierre Gaudillat

    2014-07-01

    Full Text Available We have prepared different hybrid polymer-phthalocyanine materials by solution processing, starting from two sulfonated phthalocyanines, s-CoPc and CuTsPc, and polyvinylpyrrolidone (PVP, polyethylene glycol (PEG, poly(acrylic acid-co-acrylamide (PAA-AM, poly(diallyldimethylammonium chloride (PDDA and polyaniline (PANI as polymers. We also studied the response to ammonia (NH3 of resistors prepared from these sensing materials. The solvent casted films, prepared from s-CoPc and PVP, PEG and PAA-AM, were highly insulating and very sensitive to the relative humidity (RH variation. The incorporation of s-CoPc in PDDA by means of layer-by-layer (LBL technique allowed to stabilize the film, but was too insulating to be interesting. We also prepared PANI-CuTsPc hybrid films by LBL technique. It allowed a regular deposition as evidenced by the linear increase of the absorbance at 688 nm as a function of the number of bilayers. The sensitivity to ammonia (NH3 of PANi-CuTsPc resistors was very high compared to that of individual materials, giving up to 80% of current decrease when exposed to 30 ppm NH3. Contrarily to what happens with neutral polymers, in PANI, CuTsPc was stabilized by strong electrostatic interactions, leading to a stable response to NH3, whatever the relative humidity in the range 10%–70%. Thus, the synergy of PANI with ionic macrocycles used as counteranions combined with their simple aqueous solution processing opens the way to the development of new gas sensors capable of operating in real world conditions.

  19. Method 349.0 Determination of Ammonia in Estuarine and Coastal Waters by Gas Segmented Continuous Flow Colorimetric Analysis

    Science.gov (United States)

    This method provides a procedure for the determination of ammonia in estuarine and coastal waters. The method is based upon the indophenol reaction,1-5 here adapted to automated gas-segmented continuous flow analysis.

  20. Resonance Based Micromechanical Cantilever for Gas Sensing

    Directory of Open Access Journals (Sweden)

    Subhashini. S

    2013-04-01

    Full Text Available Our world is facing some drastic changes in the climatic conditions due to the heating effect caused by various greenhouse gases. The most harmful gas among them is Carbon dioxide and is increasing at anuncontrolled rate.This paper aims in finding out the quantity of the major polluting gas carbon dioxide. The gravimetric sensor works by adsorbing the CO2 molecules on ZnO sensing layer, which alters the overall mass of the sensor. The mechanical structure is a cantilever, having its own resonant frequency. To selectively adsorbCO2 molecules from the mixture of gaseous molecules, ZnO at a specific temperature is used. As the gas molecules are adsorbed the mass increases and hence there is a change in resonant frequency. This change in frequency gives the measure of the quantity of CO2 molecules present in that environment. The major expected advantage of this technique would be the repeatability of the sensor that is used. This Quantitative analysis of CO2 would be helpful for mankind by alerting them about the environment in which they work,by proper conditioning and networking

  1. Unregulated greenhouse gas and ammonia emissions from current technology heavy-duty vehicles.

    Science.gov (United States)

    Thiruvengadam, Arvind; Besch, Marc; Carder, Daniel; Oshinuga, Adewale; Pasek, Randall; Hogo, Henry; Gautam, Mridul

    2016-11-01

    The study presents the measurement of carbonyl, BTEX (benzene, toluene, ethyl benzene, and xylene), ammonia, elemental/organic carbon (EC/OC), and greenhouse gas emissions from modern heavy-duty diesel and natural gas vehicles. Vehicles from different vocations that included goods movement, refuse trucks, and transit buses were tested on driving cycles representative of their duty cycle. The natural gas vehicle technologies included the stoichiometric engine platform equipped with a three-way catalyst and a diesel-like dual-fuel high-pressure direct-injection technology equipped with a diesel particulate filter (DPF) and a selective catalytic reduction (SCR). The diesel vehicles were equipped with a DPF and SCR. Results of the study show that the BTEX emissions were below detection limits for both diesel and natural gas vehicles, while carbonyl emissions were observed during cold start and low-temperature operations of the natural gas vehicles. Ammonia emissions of about 1 g/mile were observed from the stoichiometric natural gas vehicles equipped with TWC over all the driving cycles. The tailpipe GWP of the stoichiometric natural gas goods movement application was 7% lower than DPF and SCR equipped diesel. In the case of a refuse truck application the stoichiometric natural gas engine exhibited 22% lower GWP than a diesel vehicle. Tailpipe methane emissions contribute to less than 6% of the total GHG emissions. Modern heavy-duty diesel and natural gas engines are equipped with multiple after-treatment systems and complex control strategies aimed at meeting both the performance standards for the end user and meeting stringent U.S. Environmental Protection Agency (EPA) emissions regulation. Compared to older technology diesel and natural gas engines, modern engines and after-treatment technology have reduced unregulated emissions to levels close to detection limits. However, brief periods of inefficiencies related to low exhaust thermal energy have been shown to

  2. Methods for Gas Sensing with Single-Walled Carbon Nanotubes

    Science.gov (United States)

    Kaul, Anupama B. (Inventor)

    2013-01-01

    Methods for gas sensing with single-walled carbon nanotubes are described. The methods comprise biasing at least one carbon nanotube and exposing to a gas environment to detect variation in temperature as an electrical response.

  3. Catalytic decomposition of ammonia in fuel gas produced in pilot-scale pressurized fluidized-bed gasifier

    Energy Technology Data Exchange (ETDEWEB)

    Mojtahedi, W.; Ylitalo, M.; Maunula, T.; Abbasian, J. [Enviropower Inc., Tampere (Finland)

    1995-12-01

    Integrated Gasification Combined Cycle (IGCC) process, incorporating pressurized gasification of solid fuels (coal, peat, biomass) and hot gas cleanup, is being developed worldwide to generate power with high efficiency and in an environmentally acceptable manner. The gasifier product gas contains, among others, ammonia and to a lesser extent hydrogen cyanide (HCN) which are converted to oxides of nitrogen (NO{sub x}) when the gas is combusted in the gas turbine. Several nickel-based catalysts were developed and evaluated for decomposition of ammonia present in the gasifier product gas, at Enviropower`s 15 MW{sub th} pilot plant in coal- and biomass-gasification tests. Up to 75% of ammonia in the product gas was decomposed at 800-900{degree}C temperature range and 12-22 bar pressure. 11 refs., 12 figs., 4 tabs.

  4. Nanoscale Metal Oxide Semiconductors for Gas Sensing

    Science.gov (United States)

    Hunter, Gary W.; Evans, Laura; Xu, Jennifer C.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Michael J.

    2011-01-01

    A report describes the fabrication and testing of nanoscale metal oxide semiconductors (MOSs) for gas and chemical sensing. This document examines the relationship between processing approaches and resulting sensor behavior. This is a core question related to a range of applications of nanotechnology and a number of different synthesis methods are discussed: thermal evaporation- condensation (TEC), controlled oxidation, and electrospinning. Advantages and limitations of each technique are listed, providing a processing overview to developers of nanotechnology- based systems. The results of a significant amount of testing and comparison are also described. A comparison is made between SnO2, ZnO, and TiO2 single-crystal nanowires and SnO2 polycrystalline nanofibers for gas sensing. The TECsynthesized single-crystal nanowires offer uniform crystal surfaces, resistance to sintering, and their synthesis may be done apart from the substrate. The TECproduced nanowire response is very low, even at the operating temperature of 200 C. In contrast, the electrospun polycrystalline nanofiber response is high, suggesting that junction potentials are superior to a continuous surface depletion layer as a transduction mechanism for chemisorption. Using a catalyst deposited upon the surface in the form of nanoparticles yields dramatic gains in sensitivity for both nanostructured, one-dimensional forms. For the nanowire materials, the response magnitude and response rate uniformly increase with increasing operating temperature. Such changes are interpreted in terms of accelerated surface diffusional processes, yielding greater access to chemisorbed oxygen species and faster dissociative chemisorption, respectively. Regardless of operating temperature, sensitivity of the nanofibers is a factor of 10 to 100 greater than that of nanowires with the same catalyst for the same test condition. In summary, nanostructure appears critical to governing the reactivity, as measured by electrical

  5. First detection of gas-phase ammonia in a planet-forming disk

    CERN Document Server

    Salinas, Vachail N; Bergin, Edwin A; Cleeves, L Ilsedore; Brinch, Christian; Blake, Geoffrey A; Lis, Dariusz C; Melnick, Gary J; Panić, Olja; Pearson, John C; Kristensen, Lars; Yıldız, Umut A; van Dishoeck, Ewine F

    2016-01-01

    Nitrogen chemistry in protoplanetary disks and the freeze-out on dust particles is key to understand the formation of nitrogen bearing species in early solar system analogs. So far, ammonia has not been detected beyond the snowline in protoplanetary disks. We aim to find gas-phase ammonia in a protoplanetary disk and characterize its abundance with respect to water vapor. Using HIFI on the Herschel Space Observatory we detect, for the first time, the ground-state rotational emission of ortho-NH$_3$ in a protoplanetary disk, around TW Hya. We use detailed models of the disk's physical structure and the chemistry of ammonia and water to infer the amounts of gas-phase molecules of these species. We explore two radial distributions ( confined to $<$60 au like the millimeter-sized grains) and two vertical distributions (near the midplane where water is expected to photodesorb off icy grains) to describe the (unknown) location of the molecules. These distributions capture the effects of radial drift and vertical...

  6. Trace level analysis of mercury using urease in combination with an ammonia gas sensitive semiconductor structure

    Energy Technology Data Exchange (ETDEWEB)

    Winquist, F.; Lundstroem, I.; Danielsson, B.

    1988-10-01

    A method for the determination of mercury(II)ions at trace levels is described. The method is based on the profound inhibitory effect of mercury on the enzyme urease. The activity of the enzyme was determined by the rate of ammonia produced from urea as followed by an ammonia gas sensitive iridium thin metal film-oxide-semiconductor (IrTMOS) structure. Two systems were investigated. For the initial urease activity studies, a simple microcell was used. Also a test plate, containing dry reagent strips with all necessary chemicals was developed, making the analytical procedure very simple to perform. The test volume applied was 2 ..mu..l and the sensitivity to standard of mercury(II) ions is at least 0.005..mu..M (1.0 ng/ml). One sample could be analyzed in less than 8 minutes. Furthermore, the kinetics of sensor response versus enzyme activity is discussed.

  7. A detailed investigation of proposed gas-phase syntheses of ammonia in dense interstellar clouds

    Science.gov (United States)

    Herbst, Eric; Defrees, D. J.; Mclean, A. D.

    1987-01-01

    The initial reactions of the Herbst and Klemperer (1973) and the Dalgarno (1974) schemes (I and II, respectively) for the gas-phase synthesis of ammonia in dense interstellar clouds were investigated. The rate of the slightly endothermic reaction between N(+) and H2 to yield NH(+) and H (scheme I) under interstellar conditions was reinvestigated under thermal and nonthermal conditions based on laboratory data. It was found that the relative importance of this reaction in synthesizing ammonia is determined by how the laboratory data at low temperature are interpreted. On the other hand, the exothermic reaction between N and H3(+) to form NH2(+) + H (scheme II) was calculated to possess significant activation energy and, therefore, to have a negligible rate coefficient under interstellar conditions. Consequently, this reaction cannot take place appreciably in interstellar clouds.

  8. Hot gas stripping of ammonia and carbon dioxide from simulated and actual in situ retort waters

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, C.L.

    1979-01-01

    This study proved that ammonia and carbon dioxide could be removed from retort water by hot gas stripping and that overall transfer rates were slower than for physical desorption alone. The ammonia in solution complexed with the carbonate species with the result that the CO/sub 2/ transfer rates were linked to the relatively slower desorption of NH/sub 3/ from solution. Ionic reactions in the liquid phase limited the quantity of free NH/sub 3/ and CO/sub 2/, thus decreasing the driving forces for mass transfer. The retort water exhibited foaming tendencies that affected the interfacial area which should be taken into account if a stripping tower is considered on a larger scale. Transfer unit heights were calculated for the process conditions studied and correlated such that scaleup to increased capacities is possible.

  9. NH3 gas sensing properties of nanocrystalline ZnO based thick films.

    Science.gov (United States)

    Devi, G Sarala; Subrahmanyam, V Bala; Gadkari, S C; Gupta, S K

    2006-05-24

    Zinc acetate derived precursor used in the present sol-gel synthesis of zinc oxide nanoparticles is described. The reaction product obtained before and after reflux of propanolic zinc acetate solution have been studied by UV-vis, photoluminescence and FT-IR studies which confirm the formation of oligomeric precursor Zn4O(Ac)6 (Ac=CH3COO). The formation of approximately 7 nm zinc oxide nanoparticles were confirmed by X-ray diffraction (XRD) and Transmission electron microscopic studies (TEM). The gaseous ammonia gas sensing characteristics of the nano-zinc oxide sensor showed high sensitivity compared to sensor fabricated with commercial zinc oxide powder.

  10. Dynamic Control of Adsorption Sensitivity for Photo-EMF-Based Ammonia Gas Sensors Using a Wireless Network

    Directory of Open Access Journals (Sweden)

    Yuriy Vashpanov

    2011-11-01

    Full Text Available This paper proposes an adsorption sensitivity control method that uses a wireless network and illumination light intensity in a photo-electromagnetic field (EMF-based gas sensor for measurements in real time of a wide range of ammonia concentrations. The minimum measurement error for a range of ammonia concentration from 3 to 800 ppm occurs when the gas concentration magnitude corresponds with the optimal intensity of the illumination light. A simulation with LabView-engineered modules for automatic control of a new intelligent computer system was conducted to improve measurement precision over a wide range of gas concentrations. This gas sensor computer system with wireless network technology could be useful in the chemical industry for automatic detection and measurement of hazardous ammonia gas levels in real time.

  11. Selective differential ammonia gas sensor based on N-doped SWCNT films

    Energy Technology Data Exchange (ETDEWEB)

    Battie, Yann; Loiseau, Annick [LEM ONERA-CNRS UMR 104, 29 Av. de la Division Leclerc, 92322 Chatillon (France); Ducloux, Olivier; Thobois, Philippe [ONERA - DMPH, 29 Av. de la Division Leclerc, 92322 Chatillon (France); Susi, Toma; Kauppinen, Esko I. [NanoMaterials Group, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, 00076 Aalto, Espoo (Finland)

    2011-11-15

    The sensing performance of a micro-sensor based on a thick film of nitrogen-doped single-walled carbon nanotube (SWCNTs) is compared to a pristine SWCNTs film. Transfer length method analysis is used to extract the film sheet resistance from electrical measurements and reveals that the gas sensing mechanism is mainly attributed to the charge transfer between gas molecules and SWCNTs. We demonstrate that the sensitivity to NH{sub 3} can be improved by using a sensor based N-doped SWCNTs films while the sensitivity to NO{sub 2} and water vapour is unmodified. These unique gas-sensing properties can be used to develop a new NH{sub 3}-selective differential gas sensor. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Remote sensing and in situ measurements of methane and ammonia emissions from a megacity dairy complex: Chino, CA.

    Science.gov (United States)

    Leifer, Ira; Melton, Christopher; Tratt, David M; Buckland, Kerry N; Clarisse, Lieven; Coheur, Pierre; Frash, Jason; Gupta, Manish; Johnson, Patrick D; Leen, J Brian; Van Damme, Martin; Whitburn, Simon; Yurganov, Leonid

    2017-02-01

    Methane (CH4) and ammonia (NH3) directly and indirectly affect the atmospheric radiative balance with the latter leading to aerosol generation. Both have important spectral features in the Thermal InfraRed (TIR) that can be studied by remote sensing, with NH3 allowing discrimination of husbandry from other CH4 sources. Airborne hyperspectral imagery was collected for the Chino Dairy Complex in the Los Angeles Basin as well as in situ CH4, carbon dioxide (CO2) and NH3 data. TIR data showed good spatial agreement with in situ measurements and showed significant emissions heterogeneity between dairies. Airborne remote sensing mapped plume transport for ∼20 km downwind, documenting topographic effects on plume advection. Repeated multiple gas in situ measurements showed that emissions were persistent on half-year timescales. Inversion of one dairy plume found annual emissions of 4.1 × 10(5) kg CH4, 2.2 × 10(5) kg NH3, and 2.3 × 10(7) kg CO2, suggesting 2300, 4000, and 2100 head of cattle, respectively, and Chino Dairy Complex emissions of 42 Gg CH4 and 8.4 Gg NH3 implying ∼200k cows, ∼30% more than Peischl et al. (2013) estimated for June 2010. Far-field data showed chemical conversion and/or deposition of Chino NH3 occurs within the confines of the Los Angeles Basin on a four to six h timescale, faster than most published rates, and likely from higher Los Angeles oxidant loads. Satellite observations from 2011 to 2014 confirmed that observed in situ transport patterns were representative and suggests much of the Chino Dairy Complex emissions are driven towards eastern Orange County, with a lesser amount transported to Palm Springs, CA. Given interest in mitigating husbandry health impacts from air pollution emissions, this study highlights how satellite observations can be leveraged to understand exposure and how multiple gas in situ emissions studies can inform on best practices given that emissions reduction of one gas could increase those of

  13. Impact of interfacial interactions on optical and ammonia sensing in zinc oxide/polyaniline structures

    Indian Academy of Sciences (India)

    Mansi Dhingra; Lalit Kumar; Sadhna Shrivastava; P Senthil Kumar; S Annapoorni

    2013-08-01

    Zinc oxide/polyaniline (ZnO/PANI) hybrid structures have been investigated for their optical and gas sensing properties. ZnO nanoparticles, prepared by the sol–gel method, pressed in the form of pellets were used for gas sensing. The hybrid ZnO/PANI structure was obtained by the addition of PANI on the surface of ZnO. The UV–Vis absorption of the modified pellets show band edge at 363 nm corresponding to ZnO, while a change in the absorption peaks for PANI was observed. The possible interaction between Zn2+ of ZnO and NH-group of PANI was confirmed using Raman spectroscopy studies. The results reveal that the hybrid structures exhibit much higher sensitivity to NH3 gas at room temperature than blank ZnO, which is sensitive to NH3 gas at higher temperature. This enhancement has been attributed to the creation of active sites on the ZnO surface due to the presence of PANI.

  14. Graphene Hybrid Materials in Gas Sensing Applications †

    Science.gov (United States)

    Latif, Usman; Dickert, Franz L.

    2015-01-01

    Graphene, a two dimensional structure of carbon atoms, has been widely used as a material for gas sensing applications because of its large surface area, excellent conductivity, and ease of functionalization. This article reviews the most recent advances in graphene hybrid materials developed for gas sensing applications. In this review, synthetic approaches to fabricate graphene sensors, the nano structures of hybrid materials, and their sensing mechanism are presented. Future perspectives of this rapidly growing field are also discussed. PMID:26690156

  15. Gas sensing based on detection of light radiation from a region of modified cladding (nanocrystalline ZnO) of an optical fiber

    Science.gov (United States)

    Devendiran, S.; Sastikumar, D.

    2017-03-01

    A new type of fiber optic gas sensor is proposed by detecting a light radiated from a region of cladding modified with metal oxide (nanocrystalline ZnO). The intensity of radiated light is found to vary with different gasses and concentrations. Sensing characteristics are studied for ammonia, methanol, ethanol and acetone gasses. Gas sensitivity of the proposed sensor is compared with clad-modified fiber optic gas sensor. The new sensor exhibits enhanced sensitivity. Time response characteristics of the sensor are reported.

  16. Individual hollow and mesoporous aero-graphitic microtube based devices for gas sensing applications

    Science.gov (United States)

    Lupan, Oleg; Postica, Vasile; Marx, Janik; Mecklenburg, Matthias; Mishra, Yogendra K.; Schulte, Karl; Fiedler, Bodo; Adelung, Rainer

    2017-06-01

    In this work, individual hollow and mesoporous graphitic microtubes were integrated into electronic devices using a FIB/SEM system and were investigated as gas and vapor sensors by applying different bias voltages (in the range of 10 mV-1 V). By increasing the bias voltage, a slight current enhancement is observed, which is mainly attributed to the self-heating effect. A different behavior of ammonia NH3 vapor sensing by increasing the applied bias voltage for hollow and mesoporous microtubes with diameters down to 300 nm is reported. In the case of the hollow microtube, an increase in the response was observed, while a reverse effect has been noticed for the mesoporous microtube. It might be explained on the basis of the higher specific surface area (SSA) of the mesoporous microtube compared to the hollow one. Thus, at room temperature when the surface chemical reaction rate (k) prevails on the gas diffusion rate (DK) the structures with a larger SSA possess a higher response. By increasing the bias voltage, i.e., the overall temperature of the structure, DK becomes a limiting step in the gas response. Therefore, at higher bias voltages the larger pores will facilitate an enhanced gas diffusion, i.e., a higher gas response. The present study demonstrates the importance of the material porosity towards gas sensing applications.

  17. SnO2 thin films used as ammonia sensing layers at room temperature

    Directory of Open Access Journals (Sweden)

    Gaddari A.

    2013-09-01

    Full Text Available Gas sensors based on the SnO2 thin films were prepared by dip-coating method starting from their corresponding sols. The as-elaborated thin coatings were afterwards annealed at different temperatures during various times. Their morphology, composition and microstructure were characterized by scanning electron microscopy (SEM, energy dispersive X-ray analysis (EDX and X-ray diffraction (XRD. The results of electrical and sensing measurements indicated that the sensor annealed at 300°C for 3 hours exhibited the best sensitivity towards the detection of NH3 at room temperature.

  18. CHARACTERIZATION OF SOL-GEL FILM FOR DISSOLVED AMMONIA SENSING%氨溶胶-凝胶传感膜的特性

    Institute of Scientific and Technical Information of China (English)

    蒋亚琪; 林玲; 陈曦

    2003-01-01

    Optical sensing films using organically modified silicates (ormosils) as a matrix for the determination of ammonia in water based on immobilized a fluorescent indicator aminofluorescein (AF) have been investigated. The sensing film was stability for 6 months. The detection limit of ammonia for different kind of ormosils precursors ranges from 0.01 to 0.5 μg*ml-1 (S/N 2). The response time was less than 10 min.

  19. Recovery of Hydrogen from Ammonia Plant Tail Gas by Absorption-Hydration Hybrid Method

    Institute of Scientific and Technical Information of China (English)

    刘蓓; 王秀林; 唐绪龙; 杨兰英; 孙长宇; 陈光进

    2011-01-01

    In this work, the absorption-hydration hybrid method was used to recover (hydrogen + nitrogen) from (hydrogen + nitrogen + methane + argon) tail gas mixtures of synthetic ammonia plant through hydrate formation/dissociation. A high-pressure reactor with magnetic stirrer was used to study the separation efficiency. The in-fluences of the concentration of anti-agglomerant, temperature, pressure, initial gas-liquid volume ratio, and oil-water volume ratio on the separation efficiency were systematically investigated in the presence of tetrahydro-furan (THF). Anti-agglomerant was used to disperse hydrate particles into the condensate phase for water-in-oil emulsion system. Since nitrogen is the material for ammonia production, the objective production in our separation process is (hydrogen + nitrogen). Our experimental results show that by adopting appropriate operating conditions, high concentration of (hydrogen + nitrogen) can be obtained using the proposed technology based on forming hydrate.

  20. Nitrogen alloying of steel powder using ammonia gas in the fluidised bed

    Energy Technology Data Exchange (ETDEWEB)

    Virta, J.; Hannula, S.-P. [VTT Manuf. Technol. (Finland)

    1999-07-01

    Powder nitriding method utilising ammonia gas and fluidised bed technique was developed. The expected advantages of this method are the short processing time, low processing temperature and homogeneous nitrogen content of the powder charge. The nitrogen content of 0.4 wt.-% was achieved in 10 minutes at the temperature of 570 C for AISI 316 L powder. The nitrogen content increased linearly with the nitriding time being 6.8 wt.-% after two hours. For the control of the nitrogen content the heating-up and cooling of the powder must occur in an inert atmosphere. Because of the low processing temperatures nitrogen gas could be used. The short processing times, low processing temperatures and the use of inexpensive processing gases makes the method economically very attractive. (orig.)

  1. Optical fiber gas sensing system based on FBG filtering

    Science.gov (United States)

    Wang, Shutao

    2008-10-01

    An optical fiber gas sensing system based on the law of Beer-Lambert is designed to determine the concentration of gas. This technique relies on the fact that the target gas has a unique, well-defined absorption characteristic within the infrared region of electromagnetic spectrum. The narrow-band filtering characteristic of optical fiber Bragg grating is used to produce the narrow spectrum light signal. An aspheric objective optical fiber collimator is used in the system as an optical fiber gas sensing detector to improve the sensitivity and stability. Experimental results show there is a high measuring sensitivity at 0.01%, and the measuring range goes beyond 5%.

  2. Gas sensor with multiple internal reference electrodes and sensing electrodes

    DEFF Research Database (Denmark)

    2016-01-01

    The invention relates to a potentiometric gas sensor, or potentiometric gas detection element, with multiple internal reference electrodes and multiple sensing electrodes for determining the concentrations of gas components in a gaseous mixture. The sensor for gas detection comprises: a solid...... electrolyte, at least two sensing electrodes (SEs) in solid contact with the electrolyte, and at least two internal reference electrodes (IREs) in solid contact with the electrolyte, wherein each IRE comprises a composite material, comprising a binary mixture of a metal and a metal oxide dispersed to form...

  3. Remediation of Uranium in the Hanford Vadose Zone Using Ammonia Gas: FY 2010 Laboratory-Scale Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Szecsody, James E.; Truex, Michael J.; Zhong, Lirong; Qafoku, Nikolla; Williams, Mark D.; McKinley, James P.; Wang, Zheming; Bargar, John; Faurie, Danielle K.; Resch, Charles T.; Phillips, Jerry L.

    2010-12-01

    This investigation is focused on refining an in situ technology for vadose zone remediation of uranium by the addition of ammonia (NH3) gas. Objectives are to: a) refine the technique of ammonia gas treatment of low water content sediments to minimize uranium mobility by changing uranium surface phases (or coat surface phases), b) identify the geochemical changes in uranium surface phases during ammonia gas treatment, c) identify broader geochemical changes that occur in sediment during ammonia gas treatment, and d) predict and test injection of ammonia gas for intermediate-scale systems to identify process interactions that occur at a larger scale and could impact field scale implementation.Overall, NH3 gas treatment of low-water content sediments appears quite effective at decreasing aqueous, adsorbed uranium concentrations. The NH3 gas treatment is also fairly effective for decreasing the mobility of U-carbonate coprecipitates, but shows mixed success for U present in Na-boltwoodite. There are some changes in U-carbonate surface phases that were identified by surface phase analysis, but no changes observed for Na-boltwoodite. It is likely that dissolution of sediment minerals (predominantly montmorillonite, muscovite, kaolinite) under the alkaline conditions created and subsequent precipitation as the pH returns to natural conditions coat some of the uranium surface phases, although a greater understanding of these processes is needed to predict the long term impact on uranium mobility. Injection of NH3 gas into sediments at low water content (1% to 16% water content) can effectively treat a large area without water addition, so there is little uranium mobilization (i.e., transport over cm or larger scale) during the injection phase.

  4. Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values

    Science.gov (United States)

    Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

    2017-06-01

    We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO2-SiO2) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO2-SiO2) composite nanofibers. Such flexible inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO2-SiO2/PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO2-SiO2/PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO2, and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO2-SiO2/PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

  5. Selective and uniform growth of single-wall carbon nanotubes (SWCNTs) for gas sensing application

    Science.gov (United States)

    Alvi, M. A.; Al-Ghamdi, A. A.; Khan, Shamshad A.

    2017-03-01

    In the present work, we have synthesized uniformly distributed single-wall carbon nanotube (SWCNT) networks with a selective diameter suitable for gas sensing device. The SWCNT networks have been synthesized on 2-nm-thick iron (Fe) catalyst-coated silicon (Si) substrates by Plasma-Enhanced Chemical Vapor Deposition (PECVD). The as-grown SWCNTs were characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy techniques. Using SWCNT network, the sensitivity of ammonia (NH3) gases/vapors was recognized by their surface adsorption and desorption responses. The response curve was observed from the SWCNT network, which is due to a change in the resistance upon exposure to NH3 gas.

  6. Kinetics of oxidation of total sulfite in the ammonia-based wet flue gas desulfurization process

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Y.; Zhong, Q.; Fan, X.Y.; Wang, X.R. [Nanjing University of Science & Technology, Nanjing (China). School of Chemical Engineering

    2010-10-15

    Using bubbling apparatus, the kinetics of oxidation of total sulfite in ammonia-based wet flue gas desulfurization (FGD) process was investigated by varying concentrations of SO{sub 3}{sup 2-} and SO{sub 4}{sup 2-}, pH, temperatures and air flow. The concentration range of sulfite is 0.0044-0.026 gmol L{sup -1} and that of sulfate is 0.5-2 gmol L{sup -1}. Experiments were conducted at pH level of 4.5-6.5 and air flow ranging from 50 to 200 L h{sup -1}. In the temperature range of 303.15-333.15K, the reaction was found to be -0.5 order with respect to sulfite. The experimental findings also showed that the bisulfite could be oxidized easier than sulfite. Thus, keeping the pH level of the solution low is conducive to the oxidation of total sulfite. The apparent activation energy for the overall oxidation was calculated to be 28.0 kJ mol{sup -1}. A kinetic model has been derived according to the experimental results. The developed kinetic model, including the operating parameters SO{sub 3}2- concentration, SO{sub 4}{sup 2-} concentration, pH, temperature and air flow, can be applied to simulate the oxidation of total sulfite. This model would be useful for the design of the ammonia-based wet FGD system.

  7. Selective gas sensing for photonic crystal lasers

    DEFF Research Database (Denmark)

    Smith, Cameron; Christiansen, Mads Brøkner; Buss, Thomas

    2011-01-01

    We facilitate photonic crystal lasers to sense gases via an additional swelling polymer film. We describe the transduction transfer function and experimentally demonstrate an enhanced ethanol vapor sensitivity over 15 dB with low humidity crosstalk.......We facilitate photonic crystal lasers to sense gases via an additional swelling polymer film. We describe the transduction transfer function and experimentally demonstrate an enhanced ethanol vapor sensitivity over 15 dB with low humidity crosstalk....

  8. Gas sensing using air-guiding photonic bandgap fibers

    DEFF Research Database (Denmark)

    Ritar, Tuomo; Tuominen, J.; Ludvigsen, Hanne

    2004-01-01

    We demonstrate the high sensitivity of gas sensing using a novel air-guiding photonic bandgap fiber. The bandgap fiber is spliced to a standard single-mode fiber at the input end for easy coupling and filled with gas through the other end placed in a vacuum chamber. The technique is applied...

  9. Enhanced Sensing Characteristics in MEMS-based Formaldehyde Gas Sensor

    CERN Document Server

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

    2008-01-01

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

  10. Hydrothermal Synthesis and Ammonia Sensing Properties of WO3/Fe2O3 Nanorod Composites

    Science.gov (United States)

    Dien, Nguyen Dac; Phuoc, Luong Huu; Hien, Vu Xuan; Vuong, Dang Duc; Chien, Nguyen Duc

    2017-01-01

    WO3 nanorods (NRs) and α-Fe2O3 NRs were fabricated by hydrothermal treatment. Composites of these materials were created by mixing with ratios of 1:2, 1:1 and 2:1 in weight. Morphology, structure and composition characteristics of the WO3/Fe2O3 NRs composites were characterized by scanning electron microscopy, x-ray diffraction and energy dispersive x-ray spectroscopy analyses. The results of sensing measurements indicated that the sensor based on WO3:Fe2O3 with the ratio of 2:1 exhibited fairly good sensitivity toward NH3 at 300°C and the sensor based on WO3:Fe2O3 with the ratio of 1:1 can be used as a NH3 sensor with an operating temperature of 350°C. Selectivity and response-recovery times are suitable for practical applications. Finally, the mechanism for the improvement in the gas-sensing property was discussed.

  11. Recovery of ammonia from poultry litter using flat gas permeable membranes.

    Science.gov (United States)

    Rothrock, M J; Szögi, A A; Vanotti, M B

    2013-06-01

    The use of flat gas-permeable membranes was investigated as components of a new process to capture and recover ammonia (NH3) in poultry houses. This process includes the passage of gaseous NH3 through a microporous hydrophobic membrane, capture with a circulating dilute acid on the other side of the membrane, and production of a concentrated ammonium (NH4) salt. Bench- and pilot-scale prototype systems using flat expanded polytetrafluoroethylene (ePTFE) membranes and a sulfuric acid solution consistently reduced headspace NH3 concentrations from 70% to 97% and recovered 88% to 100% of the NH3 volatilized from poultry litter. The potential benefits of this technology include cleaner air inside poultry houses, reduced ventilation costs, and a concentrated liquid ammonium salt that can be used as a plant nutrient solution. Published by Elsevier Ltd.

  12. Membrane-Based Gas Traps for Ammonia, Freon-21, and Water Systems to Simplify Ground Processing

    Science.gov (United States)

    Ritchie, Stephen M. C.

    2003-01-01

    is when particles adhere to the hydrophobic membrane, promoting formation of a water layer about it that can blind the membrane for gas transport (Figure 1). This mechanism is the most probable cause for observed failures with the existing design. The objective of this project was to devise a strategy for choosing new membrane materials (database development and procedure), redesign of the gas trap to mitigate blinding effects, and to develop a design that can be used in ammonia and Freon-21 coolant loops.

  13. Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review

    OpenAIRE

    Jin-Huai Liu; Ling-Tao Kong; Shao-Bo Liu; Fan-Li Meng; Jin-Yun Liu; Zhen Jin; Yu-Feng Sun

    2012-01-01

    Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have b...

  14. An Exploration on Greenhouse Gas and Ammonia Production by Insect Species Suitable for Animal or Human Consumption

    NARCIS (Netherlands)

    Oonincx, D.G.A.B.; Itterbeeck, Van J.; Heetkamp, M.J.W.; Brand, van den H.; Loon, van J.J.A.; Huis, van A.

    2010-01-01

    Greenhouse gas (GHG) production, as a cause of climate change, is considered as one of the biggest problems society is currently facing. The livestock sector is one of the large contributors of anthropogenic GHG emissions. Also, large amounts of ammonia (NH3), leading to soil nitrification and acidi

  15. Effect of ammonia gas etching on growth of vertically aligned carbon nanotubes/nanofibers

    Institute of Scientific and Technical Information of China (English)

    Sang-Gook KIM; Sooh-Yung KIM; Hytmg-Woo LEE

    2011-01-01

    The etching effect of ammonia (NH3) on the growth of vertically aligned nanotubes/nanofibers (CNTs) was investigated by direct-current plasma enhanced chemical vapor deposition (DC-PECVD). NH3 gas etches Ni catalyst layer to form nanoscale islands while NH3 plasma etches the deposited amorphous carbon. Based on the etching effect of NH3 gas on Ni catalyst, the differences of growing bundles of CNTs and single strand CNTs were discussed; specifically, the amount of optimal NH3 gas etchingis different between bundles of CNTs and single strand CNTs. In contrast to the CNT carpet growth. the single strand CNT growth requires shorter etching time (5 min) than large catalytic patterns (10 min) since nano dots already form catalyst islands for CNT growth. Through removing the plasma pretreatment process, the damage from being exposed at high temperature substrate occurring during the plasma generation time is minimized. High resolution transmission electron microscopy (HTEM) shows fishbone structure of CNTs grown by PECVD.

  16. The influence of gas-particle partitioning and surface-atmosphere exchange on ammonia during BAQS-Met

    Science.gov (United States)

    Ellis, R. A.; Murphy, J. G.; Markovic, M. Z.; Vandenboer, T. C.; Makar, P. A.; Brook, J.; Mihele, C.

    2011-01-01

    The Border Air Quality and Meteorology study (BAQS-Met) was an intensive field campaign conducted in Southwestern Ontario during the summer of 2007. The focus of BAQS-Met was determining the causes of the formation of ozone and fine particulate matter (PM2.5), and of the regional significance of trans-boundary transport and lake breeze circulations on that formation. Fast (1 Hz) measurements of ammonia were acquired using a Quantum Cascade Laser Tunable Infrared Differential Absorption Spectrometer (QC-TILDAS) at the Harrow supersite. Measurements of PM2.5 ammonium, sulfate and nitrate were made using an Ambient Ion Monitor Ion Chromatograph (AIM-IC) with hourly time resolution. The median mixing ratio of ammonia was 2.5 ppb, with occasional high spikes at night resulting from local emissions. Measurements were used to assess major local emissions of NH3, diurnal profiles and gas-particle partitioning. The measurements were compared with results from A Unified Regional Air-quality Modelling System (AURAMS). While the fraction of total ammonia (NHx≡NH3 + NH4+) observed in the gas phase peaks between 0.1 and 0.8, AURAMS tended to predict fractions of either less than 0.05 or greater than 0.8. The model frequently predicted acidic aerosol, in contrast with observations wherein NHx almost always exceeded the observed equivalents of sulfate. One explanation for our observations is that the net flux of ammonia from the land surface to the atmosphere increases when aerosol sulfate is present, effectively buffering the mixing ratio of gas phase ammonia, a process not included in the model. A simple representation of an offline bi-directional flux parameterization using the ISORROPIA thermodynamic model was successful at reducing the population of zero gas fraction points, but not the higher gas fraction points.

  17. Gas sensing with surface acoustic wave devices

    Science.gov (United States)

    Martin, S. J.; Schweizer, K. S.; Ricco, A. J.; Zipperian, T. E.

    1985-03-01

    The use of a ZnO-on-Si surface acoustic wave (SAW) resonator as a gas sensor is discussed. In particular, the sensitivity of the device to organic vapors is examined. The planar nature of the SAW device, in which the acoustic energy is confined to within roughly one acoustic wavelength of the surface, makes the device extremely sensitive to surface perturbations. This characteristic has been exploited in the construction of SAW gas sensors in which the surface wave propagation characteristics are altered by species adsorbed from the ambient gas. The porous nature of the sputtered ZnO film, in conjunction with the microbalance capability of the SAW device, gives the sensor the ability to distinguish molecules on the basis of both size and mass.

  18. The application of a cavity ring-down spectrometer to measurements of ambient ammonia using traceable primary standard gas mixtures

    Science.gov (United States)

    Martin, Nicholas A.; Ferracci, Valerio; Cassidy, Nathan; Hoffnagle, John A.

    2016-08-01

    A correction for the undesirable effects of direct and indirect cross-interference from water vapour on ammonia (NH3) measurements was developed using an optical laser sensor based on cavity ring-down spectroscopy. This correction relied on new measurements of the collisional broadening due to water vapour of two NH3 spectral lines in the near infra-red (6548.6 and 6548.8 cm-1), and on the development of novel stable primary standard gas mixtures (PSMs) of ammonia prepared by gravimetry in passivated gas cylinders at 100 μmol mol-1. The PSMs were diluted dynamically to provide calibration mixtures of dry and humidified ammonia atmospheres of known composition in the nmol mol-1 range and were employed as part of establishing a metrological traceability chain to improve the reliability and accuracy of ambient ammonia measurements. The successful implementation of this correction will allow the extension of this rapid on-line spectroscopic technique to exposure chamber validation tests under controlled conditions and ambient monitoring in the field.

  19. Ultra-sensitive and selective NH3 room temperature gas sensing induced by manganese-doped titanium dioxide nanoparticles.

    Science.gov (United States)

    Tshabalala, Zamaswazi P; Shingange, Katekani; Cummings, Franscious R; Ntwaeaborwa, Odireleng M; Mhlongo, Gugu H; Motaung, David E

    2017-10-15

    The study of the fabrication of ultra-high sensitive and selective room temperature ammonia (NH3) and nitrogen dioxide (NO2) gas sensors remains an important scientific challenge in the gas sensing field. This is motivated by their harmful impact on the human health and environment. Therefore, herein, we report for the first time on the gas sensing properties of TiO2 nanoparticles doped with various concentrations of manganese (Mn) (1.0, 1.5, 2.0, 2.5 and 3.0mol.% presented as S1, S2, S3, S4 and S5, respectively), synthesized using hydrothermal method. Structural analyses showed that both undoped and Mn-doped TiO2 crystallized in tetragonal phases. Optical studies revealed that the Mn doped TiO2 nanoparticles have enhanced UV→Vis emission with a broad shoulder at 540nm, signifying induced defects by substituting Ti(4+) ions with Mn(2+). The X-ray photoelectron spectroscopy and the electron paramagnetic resonance studies revealed the presence of Ti(3+) and singly ionized oxygen vacancies in both pure and Mn doped TiO2 nanoparticles. Additionally, a hyperfine split due to Mn(2+) ferromagnetic ordering was observed, confirming incorporation of Mn ions into the lattice sites. The sensitivity, selectivity, operating temperature, and response-recovery times were thoroughly evaluated according to the alteration in the materials electrical resistance in the presence of the target gases. Gas sensing studies showed that Mn(2+) doped on the TiO2 surface improved the NH3 sensing performance in terms of response, sensitivity and selectivity. The S1 sensing material revealed higher sensitivity of 127.39 at 20 ppm NH3 gas. The sensing mechanism towards NH3 gas is also proposed. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Receptors useful for gas phase chemical sensing

    Energy Technology Data Exchange (ETDEWEB)

    Jaworski, Justyn W; Lee, Seung-Wuk; Majumdar, Arunava; Raorane, Digvijay A

    2015-02-17

    The invention provides for a receptor, capable of binding to a target molecule, linked to a hygroscopic polymer or hydrogel; and the use of this receptor in a device for detecting the target molecule in a gaseous and/or liquid phase. The invention also provides for a method for detecting the presence of a target molecule in the gas phase using the device. In particular, the receptor can be a peptide capable of binding a 2,4,6-trinitrotoluene (TNT) or 2,4,-dinitrotoluene (DNT).

  1. Gas sensing method applicable to real conditions

    Science.gov (United States)

    Szczurek, A.; Maciejewska, M.

    2013-04-01

    In this work, we tested the influence of various sampling techniques and modes of operation on the response of sensor systems under real conditions. The first system was based on diffusive sampling. The second one used a dynamic method of sampling. In the third system, a stop flow mode of operation was applied. A considerable error of target gas concentration assessment was obtained in the first two cases. The error resulted from sensor signal fluctuations encountered during their exposure either to the air at the measurement point (diffusive sampling) or to the air drawn from the measurement point (dynamic sampling). The fluctuations could be attributed to the temporal variation of physical and chemical parameters of air. The main merit of the third method consists in utilizing sensor exposure under the conditions of stopped flow for the purpose of pollutant concentration assessment. While using this method, the accuracy of target gas quantification under real conditions was comparable to the one achieved when measuring standard gases. We think that the proposed method is a valuable contribution, which addresses the increasing demand for sensor systems that perform quantitative pollution assessment in workplace air, under real conditions. This paper was presented at the Conference on Optoelectronic and Electronic Sensors held in Karpacz, Poland, on 24-27 June 2012.

  2. Statistical modelling and optimization of hydrolysis of urea to generate ammonia for flue gas conditioning

    Energy Technology Data Exchange (ETDEWEB)

    Mahalik, K. [Department of Chemical Engineering, Indian Institute of Technology (IIT), Kharagpur, P.O. Kharagpur Technology, West Bengal 721302 (India); Department of Chemical Engineering, Gandhi Institute of Engineering and Technology, Gunupur, Orissa (India); Sahu, J.N., E-mail: jay_sahu@yahoo.co.in [Department of Chemical Engineering, Indian Institute of Technology (IIT), Kharagpur, P.O. Kharagpur Technology, West Bengal 721302 (India); Department of Chemical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Patwardhan, Anand V. [Department of Chemical Engineering, Institute of Chemical Technology (ICT), Mumbai 400019 (India); Meikap, B.C. [Department of Chemical Engineering, Indian Institute of Technology (IIT), Kharagpur, P.O. Kharagpur Technology, West Bengal 721302 (India); School of Chemical Engineering, University of KwaZulu-Natal, Howard College Campus, King George V. Avenue, Durban 4041 (South Africa)

    2010-10-15

    The present study is concerned with the technique of producing a relatively small quantity of ammonia which can be used safely in a coal-fired thermal power plant to improve the efficiency of electrostatic precipitator by removing the suspended particulate material mostly fly ash, from the flue gas. In this work hydrolysis of urea has been conducted in a batch reactor at atmospheric pressure to study the different reaction variables such as reaction temperature, initial concentration and stirring speed on the conversion by using design expert software. A 2{sup 3} full factorial central composite design (CCD) has been employed and a quadratic model equation has been developed. The study reveals that conversion increases exponentially with an increase in temperature, stirring speed and feed concentration. However the stirring speed has the greatest effect on the conversion with concentration and temperature exerting least and moderate effect respectively. The values of equilibrium conversion obtained through the developed models are found to agree well with their corresponding experimental counterparts with a satisfactory correlation coefficient of 93%. The developed quadratic model was optimized using quadratic programming to maximize conversion of urea within experimental range studied. The optimum production condition has been found to be at the temperature of 130 {sup o}C, feed concentration of 4.16 mol/l and stirring speed of 400 rpm and the corresponding conversion, 63.242%.

  3. Enhancing recovery of ammonia from swine manure anaerobic digester effluent using gas-permeable membrane technology.

    Science.gov (United States)

    Dube, P J; Vanotti, M B; Szogi, A A; García-González, M C

    2016-03-01

    Gas-permeable membrane technology is useful to recover ammonia from manure. In this study, the technology was enhanced using aeration instead of alkali chemicals to increase pH and the ammonium (NH4(+)) recovery rate. Digested effluents from covered anaerobic swine lagoons containing 1465-2097 mg NH4(+)-N L(-1) were treated using submerged membranes (0.13 cm(2) cm(-3)), low-rate aeration (120 mL air L-manure(-1) min(-1)) and nitrification inhibitor (22 mg L(-1)) to prevent nitrification. The experiment included a control without aeration. The pH of the manure with aeration rose from 8.6 to 9.2 while the manure without aeration decreased from 8.6 to 8.1. With aeration, 97-99% of the NH4(+) was removed in about 5 days of operation with 96-98% recovery efficiency. In contrast, without aeration it took 25 days to treat the NH4(+). Therefore, the recovery of NH4(+) was five times faster with the low-rate aeration treatment. This enhancement could reduce costs by 70%.

  4. Amperometric sensing in the gas-phase

    Energy Technology Data Exchange (ETDEWEB)

    Knake, Rene [University of Basel, Department of Chemistry, Spitalstrasse 51, 4004 Basel (Switzerland); Jacquinot, Patrick [University of Basel, Department of Chemistry, Spitalstrasse 51, 4004 Basel (Switzerland); Hodgson, Alexia W.E. [University of Basel, Department of Chemistry, Spitalstrasse 51, 4004 Basel (Switzerland); Hauser, Peter C. [University of Basel, Department of Chemistry, Spitalstrasse 51, 4004 Basel (Switzerland)]. E-mail: peter.hauser@unibas.ch

    2005-09-06

    The design of amperometric sensors for gaseous species presents a challenge as the gas phase has to be brought into contact with a solid electrode as well as an electrolyte phase which usually is liquid. However, many species of analytical interest are electroactive, such as SO{sub 2}, NO {sub x}, O{sub 3}, CO, formaldehyde or ethanol, and electrochemical means are always attractive in designing sensors because the electronic signal is obtained directly. Therefore, different approaches have been implemented and some types of such sensors have been available commercially for quite some time. Nevertheless, many new developments with regard to an improvement of sensitivity, selectivity and in the construction of these devices have been reported over the last few years, as well as approaches to miniaturization. In this review it is attempted to give an overview of the state of the art of this field, highlighting recent developments.

  5. An Exploration on Greenhouse Gas and Ammonia Production by Insect Species Suitable for Animal or Human Consumption

    OpenAIRE

    Oonincx, Dennis G. A. B.; Joost van Itterbeeck; Heetkamp, Marcel J. W.; Henry van den Brand; van Loon, Joop J. A.; Arnold van Huis

    2010-01-01

    BACKGROUND: Greenhouse gas (GHG) production, as a cause of climate change, is considered as one of the biggest problems society is currently facing. The livestock sector is one of the large contributors of anthropogenic GHG emissions. Also, large amounts of ammonia (NH(3)), leading to soil nitrification and acidification, are produced by livestock. Therefore other sources of animal protein, like edible insects, are currently being considered. METHODOLOGY/PRINCIPAL FINDINGS: An experiment was ...

  6. Development of Polymethylmethacrylate Based Composite for Gas Sensing Application

    Directory of Open Access Journals (Sweden)

    S. Devikala

    2011-01-01

    Full Text Available Gas detection instruments are increasingly needed for industrial health and safety, environmental monitoring and process control. Conductive polymer composites have various industrial applications. The composite prepared by mixing carbon black with polymethylmethacrylate (PMMA has very good gas sensing applications. The gas sensors based on carbon nanotube/polymer, ceramic and metal oxide composites such as epoxy, polyimide, PMMA / Barium titanate and tin oxide have also been developed. In the present work, a new composite has been prepared by using PMMA and ammonium dihydrogen phosphate (ADP. The PMMA/Ammonium dihydrogen phosphate (PMADP composites PMADP 1 and PMADP 2 were characterized by using Powder XRD. The thick films of the composite on glass plates were prepared by using a spin coating unit at 9000 rpm. The application of the thick film as gas sensor has been studied between 0 and 2000 seconds. The results reveal that the thick film of PMADP composite can function as a very good gas sensor.

  7. Distributed Fiber Optic Gas Sensing for Harsh Environment

    Energy Technology Data Exchange (ETDEWEB)

    Juntao Wu

    2008-03-14

    This report summarizes work to develop a novel distributed fiber-optic micro-sensor that is capable of detecting common fossil fuel gases in harsh environments. During the 32-month research and development (R&D) program, GE Global Research successfully synthesized sensing materials using two techniques: sol-gel based fiber surface coating and magnetron sputtering based fiber micro-sensor integration. Palladium nanocrystalline embedded silica matrix material (nc-Pd/Silica), nanocrystalline palladium oxides (nc-PdO{sub x}) and palladium alloy (nc-PdAuN{sub 1}), and nanocrystalline tungsten (nc-WO{sub x}) sensing materials were identified to have high sensitivity and selectivity to hydrogen; while the palladium doped and un-doped nanocrystalline tin oxide (nc-PdSnO{sub 2} and nc-SnO{sub 2}) materials were verified to have high sensitivity and selectivity to carbon monoxide. The fiber micro-sensor comprises an apodized long-period grating in a single-mode fiber, and the fiber grating cladding surface was functionalized by above sensing materials with a typical thickness ranging from a few tens of nanometers to a few hundred nanometers. GE found that the morphologies of such sensing nanomaterials are either nanoparticle film or nanoporous film with a typical size distribution from 5-10 nanometers. nc-PdO{sub x} and alloy sensing materials were found to be highly sensitive to hydrogen gas within the temperature range from ambient to 150 C, while nc-Pd/Silica and nc-WO{sub x} sensing materials were found to be suitable to be operated from 150 C to 500 C for hydrogen gas detection. The palladium doped and un-doped nc-SnO{sub 2} materials also demonstrated sensitivity to carbon monoxide gas at approximately 500 C. The prototyped fiber gas sensing system developed in this R&D program is based on wavelength-division-multiplexing technology in which each fiber sensor is identified according to its transmission spectra features within the guiding mode and cladding modes. The

  8. Development of gas sensing application for formaldehyde gas detection and characterization of tin dioxide

    Science.gov (United States)

    Zaki, M.; Hashim, U.; Arshad, M. K. Md; Nasir, M.

    2017-03-01

    This paper presents the development of sensor in ultrasensitive detection of formaldehyde gas. The chemical compound, tin dioxide (SnO2) thin film is deposited onto glass insulator. Next, the resistance and voltage of the sensing layer on the interdigitated electrodes (IDE) sensor's substrate is measured. The resistivity of sensor is changed by heat the sensing layer to 150 °C, 175 °C and 200 °C. When formaldehyde gas is supplied inside the test chamber, absorption process occurred at the surface of the heated SnO2 sensing layer. The experimental results show the sensor is capable of high sensitivity sensing of formaldehyde gas at 200 °C, repeatability, and capability detection as low as 11 ppm which produced 0.8 V on electronic reader. Characterization of surface morphological, temperature effect and electrical properties are demonstrated by various measurements.

  9. A novel approach to Lab-In-Syringe Head-Space Single-Drop Microextraction and on-drop sensing of ammonia.

    Science.gov (United States)

    Šrámková, Ivana; Horstkotte, Burkhard; Sklenářová, Hana; Solich, Petr; Kolev, Spas D

    2016-08-31

    A novel approach to the automation technique Lab-In-Syringe, also known as In-Syringe Analysis, is proposed which utilizes a secondary inlet into the syringe void, used as a size-adaptable reaction chamber, via a channel passing through the syringe piston. This innovative approach allows straightforward automation of head-space single-drop microextraction, involving accurately controlled drop formation and handling, and the possibility of on-drop analyte quantification. The syringe was used in upside-down orientation and in-syringe magnetic stirring was carried out, which allowed homogenous mixing of solutions, promotion of head-space analyte enrichment, and efficient syringe cleaning. The superior performance of the newly developed system was illustrated with the development of a sensitive method for total ammonia determination in surface waters. It is based on head-space extraction of ammonia into a single drop of bromothymol blue indicator created inside the syringe at the orifice of the syringe piston channel and on-drop sensing of the color change via fiber optics. The slope of the linear relationship between absorbance and time was used as the analytical signal. Drop formation and performance of on-drop monitoring was further studied with rhodamine B solution to give a better understanding of the system's performance. A repeatability of 6% RSD at 10 μmol L(-1) NH3, a linear range of up to 25 μmol L(-1) NH3, and a limit of detection of 1.8 μmol L(-1) NH3 were achieved. Study of interferences proved the high robustness of the method towards humic acids, high sample salinity, and the presence of detergents, thus demonstrating the method superiority compared to the state-of-the-art gas-diffusion methods. A mean analyte recovery of 101.8% was found in analyzing spiked environmental water samples.

  10. Suppression of Fusarium wilt of cucumber by ammonia gas fumigation via reduction of Fusarium population in the field

    Science.gov (United States)

    Zhao, Jun; Mei, Zhong; Zhang, Xu; Xue, Chao; Zhang, Chenzhi; Ma, Tengfei; Zhang, Shusheng

    2017-01-01

    Cucumber plants subjected to consecutive monoculture for 9 years were found to suffer from severe Fusarium wilt disease, caused by the soil-borne fungus Fusarium oxysporum f. sp. Cucumerinum J. H. Owen. In the present study, greenhouse experiments were performed to evaluate the influence of ammonia gas fumigation on Fusarium wilt suppression, fungal abundance and fungal community composition. Results showed that ammonia gas fumigation remarkably reduced disease incidence from 80% to 27%, resulting in a four-fold increase in yield, compared to the control. Total fungal abundance declined dramatically after fumigation and reached the lowest level at day 32, at 243 times lower than the control. Moreover, fumigation significantly increased soil fungal diversity, though it also decreased considerably coinciding with cucumber growth. Fumigation also significantly altered soil fungal community composition, relative to the control. Fusarium was strongly inhibited by fumigation in both relative abundance (3.8 times lower) and targeted quantification (a decrease of 167 fold). Collectively, the application of ammonia gas fumigation to control Fusarium wilt of cucumber resulted in a re-assembly of the fungal community to resemble that of a non-disease conducive consortium. Additional strategies, such as bioorganic fertilizer application, may still be required to develop sustainable disease suppression following fumigation. PMID:28230182

  11. Effect of H{sub 2}S on the catalytic decomposition of tar and ammonia with dolomite and sintered iron ore in synthetic gasification gas

    Energy Technology Data Exchange (ETDEWEB)

    Hepola, J. [VTT Energy, Espoo (Finland)

    1996-12-31

    The toluene-decomposing activity of calcined dolomite was not affected by the H{sub 2}S content of synthetic gasification gas. Iron was active with respect to toluene and ammonia at metallic state. The increase of the H{sub 2}S content of synthetic gasification gas (0 - 500 ppmv) decreased the tar-decomposing activity but not the ammonia- decomposing activity of sintered iron ore. (author) (12 refs.)

  12. Determination of carbon number distributions of complex phthalates by gas chromatography-mass spectrometry with ammonia chemical ionization.

    Science.gov (United States)

    Di Sanzo, Frank P; Lim, Peniel J; Han, Wenning W

    2015-01-01

    An assay method for phthalate esters with a complex mixture of isomer of varying carbon numbers, such as di-isononyl phthalate (DINP) and di-isodecyl phthalate (DIDP), using gas chromatography-mass spectrometry (GC-MS) positive chemical ionization (PCI) with 5% ammonia in methane is described. GC-MS-PCI-NH3, unlike GC-MS electron ionization (EI) (GC-MS-EI) that produces generally m/z 149 ion as the main base peak and low intensity M(+) peaks, produces higher intensity (M + 1) ions that allow the determination of total (R + R') carbon number distributions based on the various R and R' alkyl groups of the di-esters moiety. The technique allows distinguishing among the various commercial DINP and DIDP plasticizers. The carbon number distributions are determined in the acceptable range of 85 mole percent (m/m). Several examples of analysis made on commercial DINP and DIDP are presented. The use of only 5% instead of 100% ammonia simplifies use of GC-MS-PCI-NH3 but still produces sufficient M + 1 ion intensities that are appropriate for the assay. In addition, use of low concentrations of ammonia mitigates potential safety aspects related to use of ammonia and provides less corrosion for the instrument hardware.

  13. Synthesis, characterization and gas sensing performance of aluminosilicate azide cancrinite

    Indian Academy of Sciences (India)

    A V BORHADE; T A KSHIRSAGAR; S G WAKCHAURE; A G DHOLI

    2016-10-01

    The present investigation deals with synthesis and gas sensing performance of Na$_8$[AlSiO$_4$]$_6$(N$_3$)$_{2.4}$(H$_2$O)$_{4.6}$ cancrinite-based thick film. The product obtained was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, thermogravimetric analysis and magic-angle spin nuclear magneticresonance (MAS NMR). The crystal structure of the product was determined from X-ray powder diffraction data by applying Rietveld refinement. Refinement showed that azide cancrinite crystallize in the space group P6$_3$. Alternate arrangement of Si and Al atoms was confirmed by single intense peak of MAS NMR analysis. For the first time, this study reports the gas sensing performance of aluminosilicate azide cancrinite. The effect of annealing andoperating temperature on gas sensing characteristic of azide cancrinite thick film is investigated systematically for various gases at different operating temperatures. This sensor was observed to be highly sensitive and selective toammonia gas.

  14. Hematite nanoplates: Controllable synthesis, gas sensing, photocatalytic and magnetic properties.

    Science.gov (United States)

    Hao, Hongying; Sun, Dandan; Xu, Yanyan; Liu, Ping; Zhang, Guoying; Sun, Yaqiu; Gao, Dongzhao

    2016-01-15

    Uniform hematite (α-Fe2O3) nanoplates exposing {001} plane as basal planes have been prepared by a facile solvothermal method under the assistance of sodium acetate. The morphological evolution of the nanoplates was studied by adjusting the reaction parameters including the solvent and the amount of sodium acetate. The results indicated that both the adequate nucleation/growth rate and selective adsorption of alcohol molecules and acetate anions contribute to the formation of the plate-like morphology. In addition, the size of the nanoplates can be adjusted from ca. 180nm to 740nm by changing the reaction parameters. Three nanoplate samples with different size were selected to investigate the gas sensing performance, photocatalytic and magnetic properties. As gas sensing materials, all the α-Fe2O3 nanoplates exhibited high gas sensitivity and stability toward n-butanol. When applied as photocatalyst, the α-Fe2O3 nanoplates show high photodegradation efficiency towards RhB. Both the gas sensing performance and the photocatalytic property of the products exhibit obvious size-dependent effect. Magnetic measurements reveal that the plate-like α-Fe2O3 particles possess good room temperature magnetic properties.

  15. Gas-sensing properties of nanocomplex metal oxide

    Institute of Scientific and Technical Information of China (English)

    CHEN Liangyuan; HE Zhusheng; YAN Tao; BAI Shouli; CHEN Aifan; LIU Chung Chiun

    2005-01-01

    The development of CuO/CeO2 nanocomposites as the sensing material of semiconductor gas sensors is reported.CuO/CeO2 nanocomplex oxide is prepared by modified sol-gel method that uses copper nitrate, cerium nitrate and ethylene glycol as precursors. The optimized synthesis parameters and processing condition have been established. The particle size and distribution, phase morphology, specific surface, electronic states of atoms and gas sensing properties have been systematically characterized by Transmission Electron Microscope (TEM), Brunauer Emmett Teller (BET), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and gas sensitivity measurement. The results show that the sensor sensitivity depends on particle size, Cu/Ce cation ratio and calcination temperature. The effects of calcinations temperature and CuO loading on the gas sensitivity are also examined. The optimum calcination temperature and the CuO content for the highest sensitivity are 600 ℃ and 12%, respectively. The combination of excellent thermal stability.and tunable sensing properties through careful control of the processing parameters and selection of material composition gives rise to novel nanocomposites attractive to the sensitive and selective detection of a variety of toxic and combustible gases.

  16. The influence of gas-particle partitioning and surface-atmosphere exchange on ammonia during BAQS-Met

    Directory of Open Access Journals (Sweden)

    R. A. Ellis

    2011-01-01

    Full Text Available The Border Air Quality and Meteorology study (BAQS-Met was an intensive field campaign conducted in Southwestern Ontario during the summer of 2007. The focus of BAQS-Met was determining the causes of the formation of ozone and fine particulate matter (PM2.5, and of the regional significance of trans-boundary transport and lake breeze circulations on that formation. Fast (1 Hz measurements of ammonia were acquired using a Quantum Cascade Laser Tunable Infrared Differential Absorption Spectrometer (QC-TILDAS at the Harrow supersite. Measurements of PM2.5 ammonium, sulfate and nitrate were made using an Ambient Ion Monitor Ion Chromatograph (AIM-IC with hourly time resolution. The median mixing ratio of ammonia was 2.5 ppb, with occasional high spikes at night resulting from local emissions. Measurements were used to assess major local emissions of NH3, diurnal profiles and gas-particle partitioning. The measurements were compared with results from A Unified Regional Air-quality Modelling System (AURAMS. While the fraction of total ammonia (NHx≡NH3 + NH4+ observed in the gas phase peaks between 0.1 and 0.8, AURAMS tended to predict fractions of either less than 0.05 or greater than 0.8. The model frequently predicted acidic aerosol, in contrast with observations wherein NHx almost always exceeded the observed equivalents of sulfate. One explanation for our observations is that the net flux of ammonia from the land surface to the atmosphere increases when aerosol sulfate is present, effectively buffering the mixing ratio of gas phase ammonia, a process not included in the model. A simple representation of an offline bi-directional flux parameterization using the ISORROPIA thermodynamic model was successful at reducing the population of zero gas fraction points, but not the higher gas fraction points.

  17. Thermally reduced kaolin-graphene oxide nanocomposites for gas sensing

    Science.gov (United States)

    Zhang, Renyun; Alecrim, Viviane; Hummelgård, Magnus; Andres, Britta; Forsberg, Sven; Andersson, Mattias; Olin, Håkan

    2015-01-01

    Highly sensitive graphene-based gas sensors can be made using large-area single layer graphene, but the cost of large-area pure graphene is high, making the simpler reduced graphene oxide (rGO) an attractive alternative. To use rGO for gas sensing, however, require a high active surface area and slightly different approach is needed. Here, we report on a simple method to produce kaolin-graphene oxide (GO) nanocomposites and an application of this nanocomposite as a gas sensor. The nanocomposite was made by binding the GO flakes to kaolin with the help of 3-Aminopropyltriethoxysilane (APTES). The GO flakes in the nanocomposite were contacting neighboring GO flakes as observed by electron microscopy. After thermal annealing, the nanocomposite become conductive as showed by sheet resistance measurements. Based on the conductance changes of the nanocomposite films, electrical gas sensing devices were made for detecting NH3 and HNO3. These devices had a higher sensitivity than thermally annealed multilayer GO films. This kaolin-GO nanocomposite might be useful in applications that require a low-cost material with large conductive surface area including the demonstrated gas sensors.

  18. Cytochrome c biosensor--a model for gas sensing.

    Science.gov (United States)

    Hulko, Michael; Hospach, Ingeborg; Krasteva, Nadejda; Nelles, Gabriele

    2011-01-01

    This work is about gas biosensing with a cytochrome c biosensor. Emphasis is put on the analysis of the sensing process and a mathematical model to make predictions about the biosensor response. Reliable predictions about biosensor responses can provide valuable information and facilitate biosensor development, particularly at an early development stage. The sensing process comprises several individual steps, such as phase partition equilibrium, intermediate reactions, mass-transport, and reaction kinetics, which take place in and between the gas and liquid phases. A quantitative description of each step was worked out and finally combined into a mathematical model. The applicability of the model was demonstrated for a particular example of methanethiol gas detection by a cytochrome c biosensor. The model allowed us to predict the optical readout response of the biosensor from tabulated data and data obtained in simple liquid phase experiments. The prediction was experimentally verified with a planar three-electrode electro-optical cytochrome c biosensor in contact with methanethiol gas in a gas tight spectroelectrochemical measurement cell.

  19. Investigation of gas sensing properties of InN nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Madapu, Kishore K., E-mail: madupu@igcar.gov.in, E-mail: dhara@igcar.gov.in; Prasad, A. K.; Tyagi, A. K.; Dhara, S., E-mail: madupu@igcar.gov.in, E-mail: dhara@igcar.gov.in [Surface and Nanoscience Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India)

    2015-06-24

    InN nanoparticles were grown by chemical vapor deposition technique using In{sub 2}O{sub 3} as precursor material. Raman spectroscopic studies show the presence of the wurtzite phase of as-grown InN. Size of the nanoparticles were in range from quantum dot (<8 nm) to larger sized particles (100 nm). We studied the gas sensing properties of InN nanoparticles with CH{sub 4} gas. Sensors substrates were fabricated with interdigitated Au electrodes. InN nanoparticles show high response towards CH{sub 4} with minimum detectable concentration of 50 ppm at 200 °C.

  20. Silicon Nanowire‐Based Devices for Gas-Phase Sensing

    Directory of Open Access Journals (Sweden)

    Anping Cao

    2013-12-01

    Full Text Available Since their introduction in 2001, SiNW-based sensor devices have attracted considerable interest as a general platform for ultra-sensitive, electrical detection of biological and chemical species. Most studies focus on detecting, sensing and monitoring analytes in aqueous solution, but the number of studies on sensing gases and vapors using SiNW-based devices is increasing. This review gives an overview of selected research papers related to the application of electrical SiNW-based devices in the gas phase that have been reported over the past 10 years. Special attention is given to surface modification strategies and the sensing principles involved. In addition, future steps and technological challenges in this field are addressed.

  1. Validation of ammonia diffusive and active samplers in a controlled atmosphere test facility using traceable Primary Standard Gas Mixtures

    Science.gov (United States)

    Martin, Nicholas A.; Ferracci, Valerio; Cassidy, Nathan; Hook, Josh; Battersby, Ross M.; Tang, Yuk S.; Stevens, Amy C. M.; Jones, Matthew R.; Braban, Christine F.; Gates, Linda; Hangartner, Markus; Stoll, Jean-Marc; Sacco, Paolo; Pagani, Diego; Hoffnagle, John A.

    2017-04-01

    Intensive animal farming, the increased use of fertilizers, and certain industrial processes are believed to be responsible for the observed increases in the amount fraction of ammonia (NH3) found in Europe. NH3 contributes to eutrophication and acidification of land and freshwater, potentially leading to a loss of biodiversity and undesirable changes to the ecosystem. It also contributes to the formation of secondary particulate matter (PM) formation, which is associated with poor air quality and adverse health outcomes. Measurements of ambient ammonia are principally carried out with low-cost diffusive samplers or by active sampling with denuders, with each method delivering time-integrated values over the monitoring period. However, such techniques have not yet been extensively validated. The goal of this work was to provide improvements in the metrological traceability through the determination of NH3 diffusive sampling rates. Five different designs of commercial diffusive samplers (FSM Radiello radial sampler, Gradko diffusion tube, Gradko DIFRAM-400, Passam ammonia sampler, and CEH ALPHA sampler) were employed, together with a pumped denuder sampler (CEH DELTA denuder) for comparison. All devices were simultaneously exposed for either 28 days or 14 days (dependent on sampler type) in a controlled atmosphere test facility (CATFAC) containing traceable amount fractions of humidified ammonia using new stable ammonia Primary Standard Gas Mixtures developed by gravimetry at NPL, under a wide range of conditions that are relevant to ambient monitoring. Online continuous monitoring of the ammonia test atmospheres was carried out by extractive sampling, employing a calibrated cavity ring-down spectrometer, which had been modified to account for cross interference by water vapour. Each manufacturer extracted the captured ammonia on the exposed samplers in the form of ammonium (NH4+) using their own accredited traceable wet chemical techniques, and then reported data

  2. Nutritive value of wheat straw treated with gaseous or liquid ammonia trough nylon bag and in vitro gas production techniques

    Directory of Open Access Journals (Sweden)

    Samad Sadeghi

    2016-04-01

    Full Text Available Introduction Feed shortage is the most important characteristic of Iranian animal industry. Increased costs of livestock production have caused the Iranian producers to reduce feed costs mainly by inclusion low quality crop residues into ruminants diets. It is estimated that around 20 million tons wheat straw produced in Iran every year. Both the digestibility and crude protein content of wheat straw are typically low. Since 1900, a wide variety of chemical treatments have been tested for their potential to improve the feeding value of wheat straw. Upgrading of wheat straw by ammoniation has been known for a long time, but application of this method of wheat straw treatment has received the least attention in the area (Khorasan Province, Iran. Therefore, the object of the present study was to evaluate the effect of gaseous and liquid ammonia on nutritive value of wheat straw through in vitro techniques. Material and Methods One kg dry wheat straw was placed into the plastic cylinders with dimension of 1 m (diameter and 1.8 m (height and 0.8 mm (thickness. Gaseous and liquid commercial ammonia was injected or added to the wrapped straw at the rate of 2, 4 and 6 percent. The treatment time was 1 month at room temperature (20-25 ºC. At the end of treatment period the cylinders were opened and the ammoniated straw exposed to the air for 4 days. The treated straws were sampled for the subsequent analyses. Dry matter degradability of the samples was done by using nylon bags (10x20 cm with pore size of 40 micron. About 2 g ground samples (2 mm were placed into the nylon bags and incubated in rumen of 4 permanently fistulated steers for 3, 6, 12, 24, 36, 48, 72, 96 and 120 hrs. The experimental steers were fed by the ordinary diet containing 65% forage and 35% concentrate twice daily. The Menke and Steingass method was followed for the in vitro gas production method. Result and discussion Crude protein (CP content of the treated wheat straw samples

  3. Water-soluble copper phthalocyanine for optimization of gas-sensor characteristics of tin dioxide upon adsorption of ammonia

    Science.gov (United States)

    Komolov, A. S.; Lazneva, E. F.; Gerasimova, N. B.; Zimina, M. V.; Si, P.; Panina, Yu. A.

    2015-12-01

    This paper presents the results of the investigation into the electrical conductivity of thin films based on tin dioxide (SnO2) nanoparticles, a film consisting of copper phthalocyanine-3,4',4″,4‴-tetrasulfonic acid tetrasodium salt (CuPc-4SO3Na) molecules, and a composite film based on a mixture of equal parts by volume of the two materials upon adsorption of ammonia. The adsorption experiments have been carried out in a vacuum at room temperature with an increase in the ammonia pressure to 3 × 103 Pa from the residual gas base pressure of 5 × 10-1 Pa. It has been found that, in the case of a single-component film based on SnO2 nanoparticles, an increase in the electrical conductivity reaches 100% and is not completely reversible at room temperature after evacuation of the gas. For the single-component CuPc-4SO3Na film and the composite CuPc-4SO3Na/SnO2 film, the electrical conductivities increase by a factor of 400 and 150, respectively. Upon evacuation of ammonia to the base pressure, the electrical conductivity decreases to the initial values for 1 s. The mechanism of the influence of adsorbed ammonia molecules on the electrical conductivity of the composite material under investigation has been discussed using the model of the formation of the composite sample, according to which the organic component is located in voids between the SnO2 nanoparticles.

  4. Zinc oxide doped graphene oxide films for gas sensing applications

    Science.gov (United States)

    Chetna, Kumar, Shani; Garg, A.; Chowdhuri, A.; Dhingra, V.; Chaudhary, S.; Kapoor, A.

    2016-05-01

    Graphene Oxide (GO) is analogous to graphene, but presence of many functional groups makes its physical and chemical properties essentially different from those of graphene. GO is found to be a promising material for low cost fabrication of highly versatile and environment friendly gas sensors. Selectivity, reversibility and sensitivity of GO based gas sensor have been improved by hybridization with Zinc Oxide nanoparticles. The device is fabricated by spin coating of deionized water dispersed GO flakes (synthesized using traditional hummer's method) doped with Zinc Oxide on standard glass substrate. Since GO is an insulator and functional groups on GO nanosheets play vital role in adsorbing gas molecules, it is being used as an adsorber. Additionally, on being exposed to certain gases the electric and optical characteristics of GO material exhibit an alteration in behavior. For the conductivity, we use Zinc Oxide, as it displays a high sensitivity towards conduction. The effects of the compositions, structural defects and morphologies of graphene based sensing layers and the configurations of sensing devices on the performances of gas sensors were investigated by Raman Spectroscopy, X-ray diffraction(XRD) and Keithley Sourcemeter.

  5. Nanocasting synthesis and gas-sensing behavior of hematite nanowires

    Science.gov (United States)

    Li, Danping; Zhang, Y.; Xu, Jingcai; Jin, Hongxiao; Jin, Dingfeng; Hong, Bo; Peng, Xiaoling; Wang, Panfeng; Ge, Hongliang; Wang, Xinqing

    2016-10-01

    The dispersed and uniform hematite nanowires (α-Fe2O3 NWs) with the different diameter were synthesized using SBA-15 as hard templates by the nanocasting method, and the diameter of α-Fe2O3 NWs was about 4, 6 and 8 nm, respectively. The BET surface area of α-Fe2O3 NWs changed a little, while the bandgap decreased from 2.07, 2.03 to 1.91 eV with the increasing diameter according to quantum size effect. Compared all samples, the sensitivity of α-Fe2O3 NWs based gas-sensors increased from 10.64 to 11.43 with the bandgap and BET surface area α-Fe2O3 NWs in 100 ppm ethanol at 300 °C, and the response-recovery time was also improved for the good crystallinity. It's concluded that the surface area greatly affected the gas-sensing performance of α-Fe2O3 NWs based sensors, while the bandgap and crystallinity also influenced the gas-sensing behavior to some extent. The α-Fe2O3 NWs based gas-sensors exhibited the high sensitivity, fast response-recovery and good selectivity to ethanol.

  6. Microstructure actuation and gas sensing by the Knudsen thermal force

    Science.gov (United States)

    Strongrich, Andrew; Alexeenko, Alina

    2015-11-01

    The generation of forces and moments on structures immersed in rarefied non-isothermal gas flows has received limited practical implementation since first being discovered over a century ago. The formation of significant thermal stresses requires both large thermal gradients and characteristic dimensions which are comparable to the gas molecular mean free path. For macroscopic geometries, this necessitates impractically high temperatures and very low pressures. At the microscale, however, these conditions are easily achieved, allowing the effects to be exploited, namely, for gas-property sensing and microstructure actuation. In this letter, we introduce and experimentally evaluate performance of a microelectromechanical in-plane Knudsen radiometric actuator, a self-contained device having Knudsen thermal force generation, sensing, and tuning mechanisms integrated onto the same platform. Sensitivity to ambient pressure, temperature gradient, as well as gas composition is demonstrated. Results are presented in terms of a non-dimensional force coefficient, allowing measurements to be directly compared to the previous experimental and computational data on out-of-plane cantilevered configurations.

  7. Zinc oxide doped graphene oxide films for gas sensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Chetna,, E-mail: chetna2288@gmail.com; Kumar, Shani; Chaudhary, S.; Kapoor, A. [Department of Electronic Science, University of Delhi South Campus, Benito Juarez Road, New Delhi-110021 (India); Garg, A.; Chowdhuri, A.; Dhingra, V. [Department of Electronic Science, Acharya Narendra Dev College, University of Delhi, Kalkaji, New Delhi- 110019 (India)

    2016-05-06

    Graphene Oxide (GO) is analogous to graphene, but presence of many functional groups makes its physical and chemical properties essentially different from those of graphene. GO is found to be a promising material for low cost fabrication of highly versatile and environment friendly gas sensors. Selectivity, reversibility and sensitivity of GO based gas sensor have been improved by hybridization with Zinc Oxide nanoparticles. The device is fabricated by spin coating of deionized water dispersed GO flakes (synthesized using traditional hummer’s method) doped with Zinc Oxide on standard glass substrate. Since GO is an insulator and functional groups on GO nanosheets play vital role in adsorbing gas molecules, it is being used as an adsorber. Additionally, on being exposed to certain gases the electric and optical characteristics of GO material exhibit an alteration in behavior. For the conductivity, we use Zinc Oxide, as it displays a high sensitivity towards conduction. The effects of the compositions, structural defects and morphologies of graphene based sensing layers and the configurations of sensing devices on the performances of gas sensors were investigated by Raman Spectroscopy, X-ray diffraction(XRD) and Keithley Sourcemeter.

  8. The microwave opacity of ammonia and water vapor: Application to remote sensing of the atmosphere of Jupiter

    Science.gov (United States)

    Hanley, Thomas Ryan

    2008-06-01

    The object of this research program has been to provide a baseline for microwave remote sensing of ammonia and water vapor in the atmosphere of Jupiter through laboratory measurements of their microwave absorption properties. Jupiter is not only the largest planet in our solar system, but one of the most interesting and complex. Despite a handful of spacecraft missions and many astronomical measurements, much of Jupiter's atmospheric dynamics and composition remain a mystery. Although constraints have been formed on the amount of certain gases present, the global abundances and distributions of water vapor (H 2 O) and ammonia (NH 3 ) are relatively unknown. Measurements of H 2 O and NH 3 in the Jovian atmosphere to hundreds of bars of pressure are best accomplished via passive microwave emission measurements. For these measurements to be accurately interpreted, however, the hydrogen and helium pressure-broadened microwave opacities of H 2 O and NH 3 must be well characterized, a task that is very difficult if based solely on theory and limited laboratory measurements. Therefore, accurate laboratory measurements have been taken under a broad range of conditions that mimic those of the Jovian atmosphere. These measurements, performed using a newly redesigned high- accuracy system, and the corresponding models of microwave opacity that have been developed from them comprise the majority of this work. The models allow more accurate retrievals of H 2 O and NH 3 abundances from previous as well as future missions to Jupiter and the outer planets, such as the NASA New Frontiers class Juno mission scheduled for launch in 2011. This information will enable a greater understanding of the concentration and distribution of H 2 O and NH 3 in the Jovian atmosphere, which will reveal much about how Jupiter and our solar system formed and how similar planets could form in other solar systems, even planets that may be hospitable to life.

  9. Substitutionally doped phosphorene: electronic properties and gas sensing

    Science.gov (United States)

    Suvansinpan, Nawat; Hussain, Fayyaz; Zhang, Gang; Hsin Chiu, Cheng; Cai, Yongqing; Zhang, Yong-Wei

    2016-02-01

    Phosphorene, a new elemental two-dimensional material, has attracted increasing attention owing to its intriguing electronic properties. In particular, pristine phospohorene, due to its ultrahigh surface-volume ratio and high chemical activity, has been shown to be promising for gas sensing (Abbas et al 2015 ACS Nano 9 5618). To further enhance its sensing ability, we perform first-principles calculations based on density functional theory to study substitutionally doped phosphorene with 17 different atoms, focusing on structures, energetics, electronic properties and gas sensing. Our calculations reveal that anionic X (X = O, C and S) dopants have a large binding energy and highly dispersive electronic states, signifying the formation of covalent X-P bonds and thus strong structural stability. Alkali atom (Li and Na) doping is found to donate most of the electrons in the outer s-orbital by forming ionic bonds with P, and the band gap decreases by pushing down the conduction band, suggesting that the optical and electronic properties of the doped phosphorene can be tailored. For doping with VIIIB-group (Fe, Co and Ni) elements, a strong affinity is predicted and the binding energy and charge transfer are correlated strongly with their electronegativity. By examining NO molecule adsorption, we find that these metal doped phosphorenes (MDPs) in general exhibit a significantly enhanced chemical activity compared with pristine phosphorene. Our study suggests that substitutionally doped phosphorene shows many intriguing electronic and optic properties different from pristine phosphorene and MDPs are promising in chemical applications involving molecular adsorption and desorption processes, such as materials growth, catalysis, gas sensing and storage.

  10. Occurrence of gas phase ammonia in the area of Beijing (China

    Directory of Open Access Journals (Sweden)

    A. Ianniello

    2010-06-01

    Full Text Available The atmospheric concentrations of gaseous ammonia have been measured during two field campaigns in the winter and in the summer of 2007 at Beijing (China. These measurements were carried out by means of diffusion annular denuders coated with phosphorous acid. The results were discussed from the standpoint of seasonal and diurnal variations and meteorological effects. The daily average NH3 concentrations were in the range of 0.20–44.38 μg/m3 and showed regular seasonal variations with higher concentrations during summer and with lower during winter. The seasonal trends seemed to be largely affected by air temperature because of agricultural sources. No diurnal variability was observed for gaseous NH3 levels in both winter and summer seasons. The highest ammonia value of 105.67 μg/m3 was measured in the early morning during the summer period when stable atmospheric conditions occurred. The diurnal winter and summer trends of ammonia were nearly independent on the air temperatures but they were affected by wind direction suggesting a strong local source influences. Ammonia was also correlated with the atmospheric mixing in the boundary layer, and, with NOx and CO air concentrations supporting the hypothesis that the traffic may be also an important source of ammonia in Beijing.

  11. A compact resonant \\Pi-shaped photoacoustic cell with low window background for gas sensing

    CERN Document Server

    Ulasevich, A L; Kouzmouk, A A; Starovoitov, V S

    2013-01-01

    A resonant photoacoustic cell capable of detecting the traces of gases at an amplitude-modulation regime is represented. The cell is designed so as to minimize the window background for the cell operation at a selected acoustic resonance. A compact prototype cell (the volume of acoustic cavity of ~ 0.2 cm^3, total cell weight of 3.5 g) adapted to the narrow diffraction-limited beam of near-infrared laser is produced and examined experimentally. The noise-associated measurement error and laser-initiated signals are studied as functions of modulation frequency. The background signal and useful response to light absorption by the gas are analyzed in measurements of absorption for ammonia traces in nitrogen flow with the help of a pigtailed DFB laser diode operated near a wavelength of 1.53 um. The performance of absorption detection and gas-leak sensing for the prototype operated at the second longitudinal acoustic resonance (the resonance frequency of ~ 4.38 kHz, Q-factor of ~ 13.9) is estimated. The noise-equi...

  12. A Miniaturized Prototype of Resonant Banana-Shaped Photoacoustic Cell for Gas Sensing

    CERN Document Server

    Ulasevich, A L; Kouzmouk, A A; Starovoitov, V S

    2013-01-01

    A resonant photoacoustic cell intended for laser-spectroscopy gas sensing is represented. This cell is a miniature imitation of a macro-scale banana-shaped cell developed previously. The parameters, which specify the cavity shape, are chosen so as not only to provide optimal cell operation at a selected acoustic resonance but also to reduce substantially the cell sizes. A miniaturized prototype cell (the volume of acoustic cavity of ~ 5 mm^3) adapted to the narrow diffraction-limited beam of near-infrared laser is produced and examined experimentally. The noise-associated measurement error and laser-initiated signals are studied as functions of modulation frequency. The background signal and the useful response to light absorption by the gas are analyzed in measurements of absorption for ammonia in nitrogen flow with the help of a pigtailed DFB laser diode oscillated near a wavelength of 1.53 um. The performance of prototype operation at the second longitudinal acoustic resonance (the resonance frequency of ~...

  13. Zn doped MoO3 nanobelts and the enhanced gas sensing properties to ethanol

    Science.gov (United States)

    Yang, Shuang; Liu, Yueli; Chen, Tao; Jin, Wei; Yang, Tingqiang; Cao, Minchi; Liu, Shunshun; Zhou, Jing; Zakharova, Galina S.; Chen, Wen

    2017-01-01

    Zn doped MoO3 nanobelts with the thickness of 120-275 nm, width of 0.3-1.4 μm and length of more than 100 μm are prepared by hydrothermal reaction. The operating temperature of sensors based on Zn doped MoO3 nanobelts is 100-380 °C with a better response to low concentration of ethanol. The highest response value of sensors based on Zn doped MoO3 to 1000 ppm ethanol at 240 °C is 321, which is about 15 times higher than that of pure MoO3 nanobelts. The gas sensors based on Zn doped MoO3 nanobelts possess good selectivity to ethanol compared with methanol, ammonia, acetone and toluene, which implies that it would be a good candidate in the potential application. The improvement of gas sensing properties may be attributed to the increasing absorbed ethanol, the decreasing probability of ethoxy recombination, the promoted dehydrogenation progress at lower temperature, and the narrowed band gap by Zn doping.

  14. Growth promoting technologies reduce greenhouse gas, alcohol, and ammonia emissions from feedlot cattle.

    Science.gov (United States)

    Stackhouse-Lawson, K R; Calvo, M S; Place, S E; Armitage, T L; Pan, Y; Zhao, Y; Mitloehner, F M

    2013-11-01

    Increased animal productivity has the potential to reduce the environmental impact per unit of consumable product and is believed to be the most promising and sustainable mitigation technique to meet increasing demand for high quality protein. The feedlot industry uses ionophores, antibiotics, growth implants, and β2-adrenergic agonists to improve health and growth performance of cattle. These technologies not only increase productivity but also alter microbes in the rumen and increase nitrogen retention in the animal, which may lead to changes in greenhouse gas (GHG), volatile organic compound (VOC), and ammonia (NH3) emissions from feedlot cattle. The present study investigated GHG, VOC, and NH3 emissions from 160 Angus crossbred steers. Steers were blocked by weight in a randomized block design and assigned to 16 pens of 10 animals each. Treatments applied were 1) control (CON; no technology application), 2) monensin and tylosin phosphate (MON), 3) monensin, tylosin phosphate, and growth implant (IMP), and 4) monensin, tylosin phosphate, growth implant, and zilpaterol hydrochloride (fed during the last 20 d of the feeding period; BAA). Cattle were on feed for an average of 107 d. Performance variables (DMI, BW, ADG, and G:F) and carcass traits (HCW, dressing percent, KPH, LM area, fat thickness, marbling score, yield grade, and quality grade) were measured. Gaseous emissions were measured during the last 10 d of the feeding period when animals were housed in 4 totally enclosed identical cattle pen enclosures. To quantify gaseous emissions a 4×4 Latin square design (n=4) was used. Gaseous emissions were analyzed using Proc Mixed in SAS and reported in grams per kilogram HCW per day and grams per kilogram per animal per hour. Treatment with IMP and BAA increased (PMethane emissions were similar for CON and IMP treated cattle. Nitrous oxide emissions were similar across CON, MON, and IMP treated cattle and were higher in BAA treated cattle (Papplication of growth

  15. Determination of ammonia and greenhouse gas emissions from land application of swine slurry: a comparison of three application methods.

    Science.gov (United States)

    Lovanh, Nanh; Warren, Jason; Sistani, Karamat

    2010-03-01

    In this study, the comparison and monitoring of the initial greenhouse gas (GHG) emissions using a flux chamber and gas analyzer from three different liquid manure application methods at a swine farm in Kentucky were carried out. Swine slurry was applied to farmland by row injection, surface spray, and Aerway injection. Ammonia and GHG concentrations were monitored immediately after application, 72 and 216h after application. The results showed that the initial ammonia flux ranged from 5.80 mg m(-2)h(-1) for the surface spray method to 1.80 mg m(-2)h(-1) for the row injection method. The initial fluxes of methane ranged from 8.75 mg m(-2)h(-1) for surface spray to 2.27 mg m(-2)h(-1) for Aerway injection, carbon dioxide ranged from 4357 mg m(-2)h(-1) for surface spray to 60 mg m(-2)h(-1) for row injection, and nitrous oxide ranged from 0.89 mg m(-2)h(-1) for surface spray to 0.22 mg m(-2)h(-1) for row injection. However, the Aerway injection method seemed to create the highest gas (GHG) concentrations inside the monitoring chambers at the initial application and produced the highest gas fluxes at subsequent sampling time (e.g., 72h after application). Nevertheless, the surface spray method appeared to produce the highest gas fluxes, and the row injection method appeared to emit the least amount of greenhouse gases into the atmosphere. Gas fluxes decreased over time and did not depend on the initial headspace concentration in the monitoring flux chambers.

  16. Exfoliated black phosphorus gas sensing properties at room temperature

    Science.gov (United States)

    Donarelli, M.; Ottaviano, L.; Giancaterini, L.; Fioravanti, G.; Perrozzi, F.; Cantalini, C.

    2016-06-01

    Room temperature gas sensing properties of chemically exfoliated black phosphorus (BP) to oxidizing (NO2, CO2) and reducing (NH3, H2, CO) gases in a dry air carrier have been reported. To study the gas sensing properties of BP, chemically exfoliated BP flakes have been drop casted on Si3N4 substrates provided with Pt comb-type interdigitated electrodes in N2 atmosphere. Scanning electron microscopy and x-ray photoelectron spectroscopy characterizations show respectively the occurrence of a mixed structure, composed of BP coarse aggregates dispersed on BP exfoliated few layer flakes bridging the electrodes, and a clear 2p doublet belonging to BP, which excludes the occurrence of surface oxidation. Room temperature electrical tests in dry air show a p-type response of multilayer BP with measured detection limits of 20 ppb and 10 ppm to NO2 and NH3 respectively. No response to CO and CO2 has been detected, while a slight but steady sensitivity to H2 has been recorded. The reported results confirm, on an experimental basis, what was previously theoretically predicted, demonstrating the promising sensing properties of exfoliated BP.

  17. Integrated Use of Hydrogen Separation by Membrane for Recovery from Ammonia Purge Gas and Ammonia Distillation%合成氨弛放气膜分离氢回收与氨蒸馏的集成应用

    Institute of Scientific and Technical Information of China (English)

    陈子香

    2011-01-01

    The ammonia purge gas contains valuable hydrogen and ammonia, and the traditional treatment method is to send the purge gas after the recovery of ammonia to the combustion system, leading to considerable waste of hydrogen. Hydrogen recovery by membrane separation and ammonia distillation are integrated into one system, so that hydrogen is recovered simultaneously with ammonia, the membrane separation technology shows higher compatibility and flexibility, and an analysis of investment and returns reflects also the economic effectiveness and rationality of this integrated method.%合成氨弛放气中含有价值较高的氢气与氨气,传统的处理方法是将弛放气回收氨气后送燃烧系统,造成了氢气的极大浪费.将膜分离氢回收与氨蒸馏集成一个系统,在回收氢气的同时回收氨,使膜分离技术具有更强的兼容性和灵活性,从投资与回报方面分析也能体现出此集成方法的经济性与合理性.

  18. Fully automated, gas sensing, and electronic parameter measurement setup for miniaturized nanoparticle gas sensors

    Science.gov (United States)

    Kennedy, M. K.; Kruis, F. E.; Fissan, H.; Mehta, B. R.

    2003-11-01

    In this study, a measurement setup has been designed and fabricated for the measurement of gas sensor characteristics and electronic parameters of nanostructured thin layers in the temperature range from room temperature to 450 °C in controlled gas environments. The setup consists of: (i) a gas environment chamber, (ii) a specially designed substrate and substrate holder, and (iii) control, supply, and measurement electronics. The buried geometry of the contacts is specially designed for the deposition of nanoparticles from the gas phase to guarantee uniform thin layers, and the setup can be used to make measurement on high resistivity (1010 Ω cm) nanoparticle samples. The gas inlet, operating temperature, and electronic control of the measurement system are automated by means of a personal computer. Coupling the measurements of interdependent gas sensing and electronic parameters at identical conditions, in a single setup encompassing a wide range of sensing gas levels and substrate temperatures, makes this system ideally suited for carrying out multiple measurements required for optimizing sensor configuration and understanding the size-dependent properties of nanoparticle sensors.

  19. Manure ammonia and greenhouse gas emissions from beef cattle fed condensed tannins

    Science.gov (United States)

    A study was conducted to determine the effects of three levels of condensed tannins fed to 27 beef feed yard steers on ammonia and GHG emissions from manure. Condensed tannins were fed at rates of 0, 0.5 and 1.0 percent on a dry matter basis. Manure and urine were collected from two periods over 6 d...

  20. A study of the effect of ammonia gas on the solid mono- and dinuclear oxorhenium(V complexes

    Directory of Open Access Journals (Sweden)

    M. M. MASHALY

    1999-09-01

    Full Text Available The reaction of ammonia gas with the solid oxorhenium(V complexes [Re2 O3L2Cl4]·2H2O, [Re2O2L3Cl6]·2H2O, [ReOLCl(OH23]Cl2, [ReOL2(OH23]CCl3, [ReOLCl3(OH2], [ReOL(SCN2Cl(OH2]·H2O and [ReOL(SCNCl2(OH2] (where L = 2-benzimadazolethione, yielded the corresponding ammine and/or amine complexes, [Re2O3L2(NH32(NH22]Cl2 (I, [Re2O2L3(NH32(NH24]Cl2 (II, [Re2O3L2(NH32 (NH24]·H2O (III, [Re2O3L4(NH24] (IV, [Re2O3L2(NH32(NH24C (V, [Re2O3L2(SCN4(NH32] (VI and [Re2O3L2(Thio2(NH24] (VII, respectively, (Thio = thiourea where ammonia gas has replaced other ligands such as chlorine and water. In complex VII thiourea replaced the thiocyanate group in the start complex through its reaction with ammonia gas. The obtained ammine and/or amine of rhenium(V complexes have been observed to decompose through several isolatable, as well as non-isolatable complex species as intermediates during heating. [Re2O3L4], [Re2O3L2(NH24] and [Re2O3L2(SCN4], were synthesized pyrolytically in the solid state from the corresponding parent oxorhenium complexes. The electronic absorption spectra and magnetic moments of the complexes show that the Re(V cation has an octahedral configuration. IR,1H-NMR spectroscopy, conductivity measurements and thermal analysies show that ammonia and thiourea behave as neutral monodentate ligands, SCN- and NH2- as monodentate monoanionic ligands, the organic ligand (L as a neutral monodentate or bidentate ligand towards the metal cation.

  1. Gas sensing properties of nanocrystalline diamond at room temperature

    Directory of Open Access Journals (Sweden)

    Marina Davydova

    2014-12-01

    Full Text Available This study describes an integrated NH3 sensor based on a hydrogenated nanocrystalline diamond (NCD-sensitive layer coated on an interdigitated electrode structure. The gas sensing properties of the sensor structure were examined using a reducing gas (NH3 at room temperature and were found to be dependent on the electrode arrangement. A pronounced response of the sensor, which was comprised of dense electrode arrays (of 50 µm separation distance, was observed. The sensor functionality was explained by the surface transfer doping effect. Moreover, the three-dimensional model of the current density distribution of the hydrogenated NCD describes the transient flow of electrons between interdigitated electrodes and the hydrogenated NCD surface, that is, the formation of a closed current loop.

  2. Tunable diameter electrostatically formed nanowire for high sensitivity gas sensing

    Institute of Scientific and Technical Information of China (English)

    Alex Henning; Nandhini Swaminathan; Andrey Godkin; Gil Shalev; Iddo Amit; Yossi Rosenwaks

    2015-01-01

    We report on an electrostatically formed nanowire (EFN)-based sensor with tunable diameters in the range of 16 nm to 46 nm and demonstrate an EFN- based field-effect transistor as a highly sensitive and robust room temperature gas sensor. The device was carefully designed and fabricated using standard integrated processing to achieve the 16 nm EFN that can be used for sensing without any need for surface modification. The effective diameter for the EFN was determined using Kelvin probe force microscopy accompanied by three- dimensional electrostatic simulations. We show that the EFN transistor is capable of detecting 100 parts per million of ethanol gas with bare SiO2.

  3. Surfactant modified SnO2 nanostructured thin film for improved sensing performance of LPG and ammonia

    Science.gov (United States)

    Kumari, K. Prasanna; Thomas, Boben

    2017-05-01

    SnO2 nanostructured thin films have been successfully synthesized by way of spray pyrolysis from surfactant added solution. The X-ray diffraction pattern discloses the tetragonal rutile phase of the deposited SnO2 films, which experience a grain size reduction from 35 nm to 19 nm, on the addition of PVP surfactant in precursor. Gas sensing investigations on the surfactant modified film show considerable LPG and NH3 response at a lower operating temperature of 150°C. Quick response (˜20s) and fast recovery (˜30s) are the main features of these sensors. The measurement of AC conductivity of the sample allows understanding the conduction mechanism and sensing action for to enhance the detection sensitivity greatly.

  4. Fast ethylamine gas sensing based on intermolecular charge-transfer complexation

    Institute of Scientific and Technical Information of China (English)

    Eun Mi Lee; Seon Young Gwon; Young A Son; Sung Hoon Kim

    2012-01-01

    We have investigated the fast ethylamine gas sensing of 2-chloro-3,5-dinitrobenzotrifluoride (CDBF) loaded poly(acrylonitrile)nanofiber based on an intermolecular charge-transfer complexation.Reversible response and recovery were achieved using alternating gas exposure.This system shows a fast ethylamine gas sensing within 0.4 s.

  5. Ammonia biofiltration and nitrous oxide generation during the start-up of gas-phase compost biofilters

    Science.gov (United States)

    Maia, Guilherme D. N.; Day V, George B.; Gates, Richard S.; Taraba, Joseph L.

    2012-01-01

    Gas-Phase Biofiltration technology is widely utilized for treating ammonia gas (NH 3) with one of its potential detrimental by-products being nitrous oxide (N 2O), a potent greenhouse gas (100-y radiative forcing 298 times greater than carbon dioxide). The present work was conducted to investigate the relation between NH 3 removal during biofiltration and N 2O generation as a product of incomplete denitrification during the start-up of gas-phase compost biofilters. Four laboratory scale tubular biofilters in up flow mode (20 s residence-time) were studied for 21 days: 3 replicates were subjected to 16 ppm v (0.78 g m -2 h -1) of NH 3 and a statistical control not subjected to NH 3. Ammonia concentration differences between biofilter inlet (Bottom = 16 ppm v) and outlet (Top) and N 2O concentration differences between biofilter outlet (Top) and biofilter inlet (background concentrations at the bottom) were used to determine the extent of the correlation between NH 3 removal and N 2O generation. Correlations with CH 4 and CO 2 were also reported. The high Spearman correlation coefficients for the three replicates ( ρ = -0.845, -0.820, and -0.841, with P ≤ 0.0001 for replications A, B and C, respectively) suggested that availability of nitrate/nitrite owing to NH 3 nitrification favored conditions for N 2O generation as a sub-product of denitrification. The statistical control received no NH 3 inputs and did not generate N 2O. Therefore, the results indicated that the process of NH 3 removal was a trigger for N 2O production. Carbon dioxide and N 2O were moderately correlated. Methane and N 2O were weakly correlated and only for replicate C. No significant correlation was found for the Statistical Control between N 2O and CH 4.

  6. Effect of dietary protein concentration on ammonia and greenhouse gas emitting potential of dairy manure.

    Science.gov (United States)

    Lee, C; Hristov, A N; Dell, C J; Feyereisen, G W; Kaye, J; Beegle, D

    2012-04-01

    Two experiments were conducted to investigate the effect of dietary crude protein concentration on ammonia (NH(3)) and greenhouse gas (GHG; nitrous oxide, methane, and carbon dioxide) emissions from fresh dairy cow manure incubated in a controlled environment (experiment 1) and from manure-amended soil (experiment 2). Manure was prepared from feces and urine collected from lactating Holstein cows fed diets with 16.7% (DM basis; HCP) or 14.8% CP (LCP). High-CP manure had higher N content and proportion of NH(3)- and urea-N in total manure N than LCP manure (DM basis: 4.4 vs. 2.8% and 51.4 vs. 30.5%, respectively). In experiment 1, NH(3) emitting potential (EP) was greater for HCP compared with LCP manure (9.20 vs. 4.88 mg/m(2) per min, respectively). The 122-h cumulative NH(3) emission tended to be decreased 47% (P=0.09) using LCP compared with HCP manure. The EP and cumulative emissions of GHG were not different between HCP and LCP manure. In experiment 2, urine and feces from cows fed LCP or HCP diets were mixed and immediately applied to lysimeters (61×61×61 cm; Hagerstown silt loam; fine, mixed, mesic Typic Hapludalf) at 277 kg of N/ha application rate. The average NH(3) EP (1.53 vs. 1.03 mg/m(2) per min, respectively) and the area under the EP curve were greater for lysimeters amended with HCP than with LCP manure. The largest difference in the NH(3) EP occurred approximately 24 h after manure application (approximately 3.5 times greater for HCP than LCP manure). The 100-h cumulative NH(3) emission was 98% greater for HCP compared with LCP manure (7,415 vs. 3,745 mg/m(2), respectively). The EP of methane was increased and that of carbon dioxide tended to be increased by LCP compared with HCP manure. The cumulative methane emission was not different between treatments, whereas the cumulative carbon dioxide emission was increased with manure from the LCP diet. Nitrous oxide emissions were low in this experiment and did not differ between treatments. In the

  7. Improved process model for ammonia volatilization from anaerobic swine lagoons under varying wind speeds and gas bubbling

    Science.gov (United States)

    Ammonia volatilization from treatment lagoons varies widely with the lagoon water total ammonia concentration, pH, temperature, suspended solids, atmospheric ammonia concentration above the water surface, and wind speed. Ammonia emissions were estimated with a process-based mechanistic model using a...

  8. A Single-Walled Carbon Nanotube Network Gas Sensing Device

    Directory of Open Access Journals (Sweden)

    I-Ju Teng

    2011-08-01

    Full Text Available The goal of this research was to develop a chemical gas sensing device based on single-walled carbon nanotube (SWCNT networks. The SWCNT networks are synthesized on Al2O3-deposted SiO2/Si substrates with 10 nm-thick Fe as the catalyst precursor layer using microwave plasma chemical vapor deposition (MPCVD. The development of interconnected SWCNT networks can be exploited to recognize the identities of different chemical gases by the strength of their particular surface adsorptive and desorptive responses to various types of chemical vapors. The physical responses on the surface of the SWCNT networks cause superficial changes in the electric charge that can be converted into electronic signals for identification. In this study, we tested NO2 and NH3 vapors at ppm levels at room temperature with our self-made gas sensing device, which was able to obtain responses to sensitivity changes with a concentration of 10 ppm for NO2 and 24 ppm for NH3.

  9. Engineering of Highly Susceptible Paramagnetic Nanostructures of Gd2S3:Eu3+: Potentially an Efficient Material for Room Temperature Gas Sensing Applications

    Directory of Open Access Journals (Sweden)

    Muhammed M. Radhi

    2010-11-01

    Full Text Available This research papers throws light into the compositional, morphological and structural properties of novel nanoparticles of Gd2S3:Eu3+ synthesized by a simple co-precipitation technique. Furthermore, we also prognosticate that this material could be useful for gas sensing applications at room temperature. Nanostructures formulation by this method resulted in the formation of orthorhombic crystal structure with primitive lattice having space group Pnma. The material characterizations are performed using X-ray diffraction (XRD, energy dispersive X-ray analysis (EDX, thermo-gravimetric analysis/differential thermal analysis (TGA/DTA and transmission electron microscope (TEM. The calculated crystallite sizes are ~ 2-5 nm and are in well accordance with the HRTEM results. EDX result confirms the presence and homogeneous distribution of Gd and Eu throughout the nanoparticle. The prepared nanoparticles exhibit strong paramagnetic nature with paramagnetic term, susceptibility c = 8.2 ´ 10-5 emg/g Gauss. TGA/DTA analysis shows 27 % weight loss with rise in temperature. The gas sensing capability of the prepared Gd2S3:Eu3+ magnetic nanoparticles are investigated using the amperometric method. These nanoparticles show good I-V characteristics with ideal semiconducting nature at room temperature with and without ammonia dose. The observed room temperature sensitivity with increasing dose of ammonia indicates applicability of Gd2S3 nanoparticles as room temperature ammonia sensors.

  10. TiO2 Nanotubes: Recent Advances in Synthesis and Gas Sensing Properties

    Directory of Open Access Journals (Sweden)

    Giorgio Sberveglieri

    2013-10-01

    Full Text Available Synthesis—particularly by electrochemical anodization-, growth mechanism and chemical sensing properties of pure, doped and mixed titania tubular arrays are reviewed. The first part deals on how anodization parameters affect the size, shape and morphology of titania nanotubes. In the second part fabrication of sensing devices based on titania nanotubes is presented, together with their most notable gas sensing performances. Doping largely improves conductivity and enhances gas sensing performances of TiO2 nanotubes

  11. Scale-Up Information for Gas-Phase Ammonia Treatment of Uranium in the Vadose Zone at the Hanford Site Central Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhong, Lirong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Thomle, Jonathan N. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Timothy C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-09-01

    Uranium is present in the vadose zone at the Hanford Central Plateau and is of concern for protection of groundwater. The Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau identified gas-phase treatment and geochemical manipulation as potentially effective treatment approaches for uranium and technetium in the Hanford Central Plateau vadose zone. Based on laboratory evaluation, use of ammonia vapor was selected as the most promising uranium treatment candidate for further development and field testing. While laboratory tests have shown that ammonia treatment effectively reduces the mobility of uranium, additional information is needed to enable deployment of this technology for remediation. Of importance for field applications are aspects of the technology associated with effective distribution of ammonia to a targeted treatment zone, understanding the fate of injected ammonia and its impact on subsurface conditions, and identifying effective monitoring approaches. In addition, information is needed to select equipment and operational parameters for a field design. As part of development efforts for the ammonia technology for remediation of vadose zone uranium contamination, field scale-up issues were identified and have been addressed through a series of laboratory and modeling efforts. This report presents a conceptual description for field application of the ammonia treatment process, engineering calculations to support treatment design, ammonia transport information, field application monitoring approaches, and a discussion of processes affecting the fate of ammonia in the subsurface. The report compiles this information from previous publications and from recent research and development activities. The intent of this report is to provide technical information about these scale-up elements to support the design and operation of a field test for the ammonia treatment technology.

  12. Techniques for measuring ammonia in fly ash, mortar, and concrete

    Energy Technology Data Exchange (ETDEWEB)

    Rathbone, R.F. [Kentucky Univ., Lexington, KY (United States). Center for Applied Energy Reseach; Majors, R.K. [Boral Material Technologies, Inc., San Antonio, TX (United States). Engineered Materials

    2003-12-01

    The presence of ammonia in fly ash that is to be used in mortar and concrete is of increasing concern in the U.S., mainly due to the installation of selective catalytic reduction (SCR) DeNOx systems. When the SCR catalyst is new, contamination of the fly ash with ammonia is generally not a concern. However, as the catalyst in the SCR ages and becomes less efficient, the ammonia slip increases and results in a greater amount of ammonium salt being precipitated on the fly ash. The increase in ammonia concentration is compounded by variability that can occur on a day-to-day basis. When marketing ammonia-laden fly ash for use in mortar and concrete it is imperative that the concentration of ammonia is known. However, there currently is no widely accepted or ''standard'' method for ammonia measurement in fly ash. This paper describes two methods that have been developed and used by the University of Kentucky Center for Applied Energy Research and Boral Material Technologies, Inc. One of the methods uses gas detection tubes and can provide an accurate determination within five to ten minutes. Thus it is suitable as a rapid field technique. The other method employs a gas-sensing electrode and requires a longer period of time to complete the measurement. However, this second method can also be used to determine the quantity of ammonia in fresh mortar and concrete. (orig.)

  13. A high-sensitivity chemical sensor based on titania coated optical-fiber long period grating for ammonia sensing in water

    Science.gov (United States)

    Tiwari, D.; James, S. W.; Tatam, R. P.; Korposh, S.; Lee, S. W.

    2015-07-01

    Two highly sensitive ammonia sensors, formed by depositing coatings composed of titanium dioxide (TiO2) onto the cladding of an optical fibre sensing platform, are evaluated. A long period grating (LPG) of period 111 μm was fabricated in the core of an optical fibre so that the LPG operates at or near the phase matching turning point (PMTP). The first coating that was investigated was composed of TiO2 nanoparticles deposited by liquid phase deposition. The sensor showed high sensitivity and allowed low concentrations of ammonia in water (0.01 ppm) to be detected with a response time of less than 60 sec. The second coating was composed of TiO2 with subsequent layers of poly (allyamine hydrochloride) (PAH), and SiO2 nanospheres infused with a sensitive element composed of porphine. The ammonia adsorption to the porphine compound led to the changes in the LPG's transmission spectrum and allowed 0.1 ppm of ammonia in water to be detected with a response time of less than 60 sec.

  14. Understanding the gas sensing properties of polypyrrole coated tin oxide nanofiber mats

    Science.gov (United States)

    Bagchi, Sudeshna; Ghanshyam, C.

    2017-03-01

    Tin oxide-polypyrrole composites have been widely studied for their enhanced sensing performance towards ammonia vapours, but further investigations are required for an understanding of the interaction mechanisms with different target analytes. In this work, polypyrrole coated tin oxide fibers have been synthesized using a two-step approach of electrospinning and vapour phase polymerization for the sensing of ammonia, ethanol, methanol, 2-propanol and acetone vapours. The resistance variation in the presence of these vapours of different nature and concentration is investigated for the determination of sensor response. A decrease in resistance occurred on interaction of tin oxide-polypyrrole with ammonia, as opposed to previous reported works. Partial reduction of polypyrrole due to interfacial interaction with tin oxide has been proposed to explain this behavior. High sensitivity of 7.45 is achieved for 1 ppm ammonia concentration. Furthermore, the sensor exhibited high sensitivity and a faster response towards ethanol vapours although methanol has the highest electron donating capability. The catalytic mechanism has been discussed to explain this interesting behavior. The results reveal that interaction between tin oxide and polypyrrole is crucial to control the predominant sensing mechanism.

  15. Simultaneous removal of SO2 and NOx with ammonia combined with gas-phase oxidation of NO using ozone

    Directory of Open Access Journals (Sweden)

    Guo Shaopeng

    2015-01-01

    Full Text Available A process for simultaneous desulfurization and denitrification was proposed, which was made up of ozone as the oxidizing agent for NO and ammonia solution as absorbent. The results showed that the presence of SO2 and the concentration changes of NO and SO2 have little impact on the oxidation of NO, the oxidation efficiency of NO can achieve over 90% when the molar ratio of O3/NO is 1.0. The presence of NOx had little effects on the absorption of SO2, an appropriate increase of SO2 concentration was favorable to the NOx absorption. The removal efficiency of SO2 and NOx reached 99.34% and 90.01% at pH 10, flow rate 0.95 Nm3/h, n[O3]/n[NO] 1.0, initial SO2 concentration 2000 mg/Nm3, initial NO concentration 200 mg/Nm3, ammonia concentration 0.3%, oxygen content of the simulated flue gas 12%, oxidation reaction temperature 423K and absorption reaction temperature 298K in the experimental system.

  16. Antibody-integrated and functionalized graphite-encapsulated magnetic beads, produced using ammonia gas plasma technology, for capturing Salmonella.

    Science.gov (United States)

    Sakudo, Akikazu; Chou, Han; Nagatsu, Masaaki

    2015-03-01

    Salmonella spp. is the single and most important causative agent of foodborne infections, especially involving foods such as eggs, milk and meat. To prevent infection, a reliable surveillance system is required that can quickly and sensitively detect Salmonella. Here, we describe the development of antibody-integrated magnetic beads that are functionalized by a novel strategy using ammonia gas plasma. Ammonia plasma, produced by a radio frequency (RF) power supply, was allowed to react with the surface of graphite-encapsulated magnetic beads, resulting in the introduction of amino groups. An anti-Salmonella antibody was then anchored by sulfide groups present on the protein surface to the amino groups of the magnetic beads via N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP). The potential usefulness of these magnetic beads for capturing Salmonella was examined as follows. The beads were incubated with Salmonella in liquid medium and then separated from the supernatant by applying a magnetic field. After thorough washing, adsorption of Salmonella to the beads was confirmed by immunochromatography, polymerase chain reaction and a direct culture assay. Our findings indicate that the capture and concentration of Salmonella using the antibody-integrated magnetic beads was more efficient than commercial Dynabeads® anti-Salmonella, which are conventionally used for concentrating Salmonella from liquid cultures. We believe this novel bead technology will contribute to the enhanced detection of Salmonella. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Gold/polypyrrole nanorods for gas sensing application

    Science.gov (United States)

    Šetka, Milena; Drbohlavová, Jana; Vallejos, Stella; Márik, Marian; Llobet, Eduard; Hubálek, Jaromír.

    2017-06-01

    This work describes the preparation of gold/polypyrrole nanorods (AuPPy NRs) using anodized alumina oxide (AAO) template and both pulsed galvanic deposition and electropolymerization for the deposition of Au and polypyrrole (PPy) nanorods (NRs), respectively. Characterization of the whole structure after AAO etching revealed the formation of a high density of NRs along the substrate with uniform diameters of approximately 50 nm and total lengths of 700 nm, the last corresponding to 1/3 and 2/3 of the length of the Au and PPy NRs, respectively. These structures are provided of bottom/top electrodes and a heating element coupled to the backside of the substrate, and their gas sensing properties towards various concentrations of NO2 in resistive configuration are presented.

  18. Gas Sensing Properties of Ordered Mesoporous SnO2

    Directory of Open Access Journals (Sweden)

    Michael Tiemann

    2006-04-01

    Full Text Available We report on the synthesis and CO gas-sensing properties of mesoporoustin(IV oxides (SnO2. For the synthesis cetyltrimethylammonium bromide (CTABr wasused as a structure-directing agent; the resulting SnO2 powders were applied as films tocommercially available sensor substrates by drop coating. Nitrogen physisorption showsspecific surface areas up to 160 m2·g-1 and mean pore diameters of about 4 nm, as verifiedby TEM. The film conductance was measured in dependence on the CO concentration inhumid synthetic air at a constant temperature of 300 °C. The sensors show a high sensitivityat low CO concentrations and turn out to be largely insensitive towards changes in therelative humidity. We compare the materials with commercially available SnO2-basedsensors.

  19. Atmospheric aerosol and gas sensing using Scheimpflug lidar

    Science.gov (United States)

    Mei, Liang; Brydegaard, Mikkel

    2015-04-01

    This work presents a new lidar technique for atmospheric remote sensing based on Scheimpflug principle, which describes the relationship between nonparallel image- and object-planes[1]. When a laser beam is transmitted into the atmosphere, the implication is that the backscattering echo of the entire illuminated probe volume can be in focus simultaneously without diminishing the aperture. The range-resolved backscattering echo can be retrieved by using a tilted line scan or two-dimensional CCD/CMOS camera. Rather than employing nanosecond-pulsed lasers, cascade detectors, and MHz signal sampling, all of high cost and complexity, we have developed a robust and inexpensive atmospheric lidar system based on compact laser diodes and array detectors. We present initial applications of the Scheimpflug lidar for atmospheric aerosol monitoring in bright sunlight, with a 3 W, 808 nm CW laser diode. Kilohertz sampling rates are also achieved with applications for wind speed and entomology [2]. Further, a proof-of-principle demonstration of differential absorption lidar (DIAL) based on the Scheimpflug lidar technique is presented [3]. By utilizing a 30 mW narrow band CW laser diode emitting at around 760 nm, the detailed shape of an oxygen absorption line can be resolved remotely with an integration time of 6 s and measurement cycle of 1 minute during night time. The promising results demonstrated in this work show potential for the Scheimpflug lidar technique for remote atmospheric aerosol and gas sensing, and renews hope for robust and realistic instrumentation for atmospheric lidar sensing. [1] F. Blais, "Review of 20 years of range sensor development," Journal of Electronic Imaging, vol. 13, pp. 231-243, Jan 2004. [2] M. Brydegaard, A. Gebru, and S. Svanberg, "Super resolution laser radar with blinking atmospheric particles - application to interacting flying insects " Progress In Electromagnetics Research, vol. 147, pp. 141-151, 2014. [3] L. Mei and M. Brydegaard

  20. Catalytic hydrolysis of urea with fly ash for generation of ammonia in a batch reactor for flue gas conditioning and NOx reduction

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, J.N.; Gangadharan, P.; Patwardhan, A.V.; Meikap, B.C. [Indian Institute of Technology, Kharagpur (India). Dept. of Chemical Engineering

    2009-01-15

    Ammonia is a highly volatile noxious material with adverse physiological effects, which become intolerable even at very low concentrations and present substantial environmental and operating hazards and risk. Yet ammonia has long been known to be used for feedstock of flue gas conditioning and NOx reduction. Urea as the source of ammonia for the production of ammonia has the obvious advantages that no ammonia shipping, handling, and storage is required. The process of this invention minimizes the risks and hazards associated with the transport, storage, and use of anhydrous and aqueous ammonia. Yet no such rapid urea conversion process is available as per requirement of high conversion in shorter time, so here we study the catalytic hydrolysis of urea for fast conversion in a batch reactor. The catalyst used in this study is fly ash, a waste material originating in great amounts in combustion processes. A number of experiments were carried out in a batch reactor at different catalytic doses, temperatures, times, and at a constant concentration of urea solution 10% by weight, and equilibrium and kinetic studies have been made.

  1. Synthesis, characterization and gas sensing property of hydroxyapatite ceramic

    Indian Academy of Sciences (India)

    M P Mahabole; R C Aiyer; C V Ramakrishna; B Sreedhar; R S Khairnar

    2005-10-01

    Hydroxyapatite (HAp) biomaterial ceramic was synthesized by three different processing routes viz. wet chemical process, microwave irradiation process, and hydrothermal technique. The synthesized ceramic powders were characterized by SEM, XRD, FTIR and XPS techniques. The dielectric measurements were carried out as a function of frequency at room temperature and the preliminary study on CO gas sensing property of hydroxyapatite was investigated. The XRD pattern of the hydroxyapatite biomaterial revealed that hydroxyapatite ceramic has hexagonal structure. The average crystallite size was found to be in the range 31–54 nm. Absorption bands corresponding to phosphate and hydroxyl functional groups, which are characteristic of hydroxyapatite, were confirmed by FTIR. The dielectric constant was found to vary in the range 9–13 at room temperature. Hydroxyapatite can be used as CO gas sensor at an optimum temperature near 125°C. X-ray photoelectron spectroscopic studies showed the Ca/P ratio of 1.63 for the HAp sample prepared by chemical process. The microwave irradiation technique yielded calcium rich HAp whereas calcium deficient HAp was obtained by hydrothermal method.

  2. Incoporating Ammonia Synthesis for an Offshore Gas-to-Liquid Process

    OpenAIRE

    2016-01-01

    The world energy demand is increasing, and so is the demand for fertilizer to sustain an exponential population growth. Currently, with low oil prices, asso- ciated natural gas is flared off or re-injected into oil reservoirs for enhanced oil recovery (EOR). A gas-to-liquid process (GTL) for offshore applications aboard a foating production, storage, and offoading vessel (FPSO) incorpo- rating Fischer-Tropsch Synthesis (FTS) seeks to reform natural gas into more valuable liq...

  3. Combustion synthesis of tin dioxide nanocomposites for gas sensing applications

    Science.gov (United States)

    Bakrania, Smitesh Dhirajlal

    The current work focuses on understanding the mechanisms controlling tin dioxide (SnO2) nanoparticle morphology in combustion synthesis systems and how nanoarchitecture affects performance of solid-state gas sensors. A range of analytical methods (including transmission and scanning electron microscopy, x-ray diffraction, nitrogen absorption, and XEDS) were used to characterize the materials properties as a function of the combustion synthesis conditions. A novel method of generating tin dioxide materials was developed which provides a new degree of control over SnO2 morphology; including spherical, nanorod and encapsulated particle architectures. A simplified model for particle formation based on characteristic times was developed to identify the physical and chemical processes affecting the morphologies observed using transmission electron microscope imaging. The SnO2 nanoparticles evolve from primary particles sizes of 7 nm to 14 nm through the synthesis region, and the results indicate interparticle collision and sintering are the dominant mechanisms in determining particle size and morphology for the flame conditions studied. Metal acetates were used to create metal/SnO 2 nanocomposite materials, and the processes controlling gold acetate decomposition in particular were explored. The results of the studies suggest a relationship between the precursor crystallite size and the product nanoparticles. The well-characterized SnO2 particles were evaluated as the active materials for gas-sensing. Sensor sensitivity and time response to carbon monoxide in dry air was used to investigate microstructure-performance links. Excellent sensitivity (3 7, based on the ratio of the resistance of the sensor in air to the resistance in the target gas) and time response (4--20 seconds) were demonstrated for the thin film gas sensors. Fabrication studies demonstrated the sensor performance was a strong function of the film deposition method. A novel method for manufacturing

  4. Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics.

    Science.gov (United States)

    Liu, Jianqiao; Gao, Yinglin; Wu, Xu; Jin, Guohua; Zhai, Zhaoxia; Liu, Huan

    2017-08-10

    The density of oxygen vacancies in semiconductor gas sensors was often assumed to be identical throughout the grain in the numerical discussion of the gas-sensing mechanism of the devices. In contrast, the actual devices had grains with inhomogeneous distribution of oxygen vacancy under non-ideal conditions. This conflict between reality and discussion drove us to study the formation and migration of the oxygen defects in semiconductor grains. A model of the gradient-distributed oxygen vacancy was proposed based on the effects of cooling rate and re-annealing on semiconductive thin films. The model established the diffusion equations of oxygen vacancy according to the defect kinetics of diffusion and exclusion. We described that the steady-state and transient-state oxygen vacancy distributions, which were used to calculate the gas-sensing characteristics of the sensor resistance and response to reducing gases under two different conditions. The gradient-distributed oxygen vacancy model had the applications in simulating the sensor performances, such as the power law, the grain size effect and the effect of depletion layer width.

  5. Inhomogeneous Oxygen Vacancy Distribution in Semiconductor Gas Sensors: Formation, Migration and Determination on Gas Sensing Characteristics

    Directory of Open Access Journals (Sweden)

    Jianqiao Liu

    2017-08-01

    Full Text Available The density of oxygen vacancies in semiconductor gas sensors was often assumed to be identical throughout the grain in the numerical discussion of the gas-sensing mechanism of the devices. In contrast, the actual devices had grains with inhomogeneous distribution of oxygen vacancy under non-ideal conditions. This conflict between reality and discussion drove us to study the formation and migration of the oxygen defects in semiconductor grains. A model of the gradient-distributed oxygen vacancy was proposed based on the effects of cooling rate and re-annealing on semiconductive thin films. The model established the diffusion equations of oxygen vacancy according to the defect kinetics of diffusion and exclusion. We described that the steady-state and transient-state oxygen vacancy distributions, which were used to calculate the gas-sensing characteristics of the sensor resistance and response to reducing gases under two different conditions. The gradient-distributed oxygen vacancy model had the applications in simulating the sensor performances, such as the power law, the grain size effect and the effect of depletion layer width.

  6. Molecular structure, optical, electrical and sensing properties of PANI-based coatings with silver nanoparticles deposited from the active gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Ragachev, A.A., E-mail: rogachev78@mail.ru [International Chinese-Belorussian Scientific Laboratory on Vacuum-Plasma Technology, College of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); National Research Tomsk Polytechnic University, 30, Lenin Avenue, Tomsk 634050 (Russian Federation); Yarmolenko, M.A. [International Chinese-Belorussian Scientific Laboratory on Vacuum-Plasma Technology, College of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); National Research Tomsk Polytechnic University, 30, Lenin Avenue, Tomsk 634050 (Russian Federation); Xiaohong, Jiang [International Chinese-Belorussian Scientific Laboratory on Vacuum-Plasma Technology, College of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Shen, Ruiqi [Key Lab of Soft Chemistry and Functional Materials of Ministry of Education, Nanjing University of Science and Technology, Nanjing 210094 (China); Luchnikov, P.A. [National Research Tomsk Polytechnic University, 30, Lenin Avenue, Tomsk 634050 (Russian Federation); Rogachev, A.V. [Francisk Skorina Gomel State University, 104, Sovetskaya Street, Gomel 246019 (Belarus)

    2015-10-01

    Highlights: • PANI-based coatings were deposited by plasma chemical solvent-free method. • PANI + AgCl coating has a partially doped structure with low variation in size of oxidized and reduced PANI units. • The increasing of the sensing performance of this coating was established at the low frequency region of impedance spectra. - Abstract: The plasma chemical solvent-free method of doped and nanocomposite polyaniline-based (PANI-based) conductive coatings deposition was elaborated. Molecular structure, morphology, optical, electrical and sensing properties of PANI-based coating were investigated by Fourier transform infrared, UV–vis, impedance spectroscopy methods and transmittance electron microscopy. The synthesized PANI-based coatings containing silver nanoparticles have a partially doped structure with low variation in size of oxidized and reduced PANI units. The nanocomposite PANI-based coatings were deposited onto interdigital capacitor for ammonia gas sensing applications. The increasing of the sensing performance of the PANI-based coatings with silver nanoparticles was established in particular at the low frequency region of impedance spectra. The high sensitivity and linearity of this sensor response were examined at a direct and alternating voltage with ammonia concentrations up to 10 ppm.

  7. [Ammonia gas concentration and velocity measurement using tunable diode laser absorption spectroscopy and optical signal cross-correlation method].

    Science.gov (United States)

    Zhang, Chun-Xiao; Wang, Fei; Li, Ning; Yan, Jian-Hua; Chi, Yong; Cen, Ke-Fa

    2009-10-01

    Simultaneous online measurement of gas concentration and velocity can be realized by tunable diode laser absorption spectroscopy (TDLAS) technique and optical signal cross-correlation method. The fundamental and relative factors of gas concentration and velocity measurement are described in the present paper. The spectral lines of NH3 used for gas sensing at communication band in near infrared range were selected and analyzed by the calculation based on the HITRAN database. In the verification experiment, NH3 and N2 were mixed by two mass flow meters and sent to flow through the quartz tube 0. 016 m in inner diameter and 1 m in length at normal temperature and pressure. The spectral line located at 6,548.7 cm(-1) was scanned at high frequency by the diode laser of 15 MHz linewidth and 1 cm' tunable range with no mode hoppings. The instantaneous NH3 absorbance was obtained using direct absorption method and the gas concentration was calculated. At the same time, the non-intrusive optical absorption signal cross-correlation method was utilized to obtain two concentration signals from two adjacent detectors mounted along the gas tube. The corresponding transit time of gas passing through the detectors was calculated by cross-correlation algorithm, and the average gas velocity was inferred according to the distance between the two detectors and the transit time. The relative errors were less than 7% for the gas concentration measurement, and less than 10% for the gas velocity measurement. Experimental results were proved to be of high precision and good repeatability in the lab. The feature of fast response and capacity immune to the in situ disturbance would lead to a potential in industry application for the real time measurement and control of gas pollutant emission in the future.

  8. Purge gas recovery of ammonia synthesis plant by integrated configuration of catalytic hydrogen-permselective membrane reactor and solid oxide fuel cell as a novel technology

    Science.gov (United States)

    Siavashi, Fakhteh; Saidi, Majid; Rahimpour, Mohammad Reza

    2014-12-01

    The purge gas emission of ammonia synthesis plant which contains hazardous components is one of the major sources of environmental pollution. Using integrated configuration of catalytic hydrogen-permselective membrane reactor and solid oxide fuel cell (SOFC) system is a new approach which has a great impact to reduce the pollutant emission. By application of this method, not only emission of ammonia and methane in the atmosphere is prevented, hydrogen is produced through the methane steam reforming and ammonia decomposition reactions that take place simultaneously in a catalytic membrane reactor. The pure generated hydrogen by recovery of the purge gas in the Pd-Ag membrane reactor is used as a feed of SOFC. Since water is the only byproduct of the electrochemical reaction in the SOFC, it is recycled to the reactor for providing the required water of the reforming reaction. Performance investigation of the reactor represents that the rate of hydrogen permeation increases with enhancing the reactor temperature and pressure. Also modeling results indicate that the SOFC performance improves with increasing the temperature and fuel utilization ratio. The generated power by recovery of the purging gas stream of ammonia synthesis plant in the Razi petrochemical complex is about 8 MW.

  9. Gas sensing of ruthenium implanted tungsten oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tesfamichael, T., E-mail: t.tesfamichael@qut.edu.au [Institute for Future Environments, School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000 (Australia); Ahsan, M. [William A. Cook Australia, 95 Brandl Street Eight Mile Plains, Brisbane, QLD 4113 (Australia); Notarianni, M. [Institute for Future Environments, School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000 (Australia); Groß, A.; Hagen, G.; Moos, R. [University of Bayreuth, Faculty of Engineering Science, Department of Functional Materials, Universitätsstr. 30, 95440 Bayreuth (Germany); Ionescu, M. [ANSTO, Institute for Environmental Research, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Bell, J. [Institute for Future Environments, School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, 2 George Street, Brisbane, QLD 4000 (Australia)

    2014-05-02

    Different amounts of Ru were implanted into thermally evaporated WO{sub 3} thin films by ion implantation. The films were subsequently annealed at 600 °C for 2 h in air to remove defects generated during the ion implantation. The Ru concentrations of four samples have been quantified by Rutherford Backscattering Spectrometry as 0.8, 5.5, 9 and 11.5 at.%. The un-implanted WO{sub 3} films were highly porous but the porosity decreased significantly after ion implantation as observed by Transmission Electron Microscopy and Scanning Electron Microscopy. The thickness of the films also decreased with increasing Ru-ion dose, which is mainly due to densification of the porous films during ion implantation. From Raman Spectroscopy two peaks at 408 and 451 cm{sup −1} (in addition to the typical vibrational peaks of the monoclinic WO{sub 3} phase) associated with Ru were observed. Their intensity increased with increasing Ru concentration. X-ray Photoelectron Spectroscopy showed a metallic state of Ru with binding energy of Ru 3d{sub 5/2} at 280.1 eV. This peak position remained almost unchanged with increasing Ru concentration. The resistances of the Ru-implanted films were found to increase in the presence of NO{sub 2} and NO with higher sensor response to NO{sub 2}. The effect of Ru concentration on the sensing performance of the films was not explicitly observed due to reduced film thickness and porosity with increasing Ru concentration. However, the results indicate that the implantation of Ru into WO{sub 3} films with sufficient film porosity and film thickness can be beneficial for NO{sub 2} sensing at temperatures in the range of 250 °C to 350 °C. - Highlights: • Densification of WO{sub 3} thin films has occurred after Ru ion implantation. • Thickness and porosity of the films decrease with increasing Ru ion dose. • The amount of oxygen vacancies and defects increases with increasing Ru ion dose. • Ru has shown a crucial role in enhancing sensor response

  10. Semipermeable Elastic Microcapsules for Gas Capture and Sensing.

    Science.gov (United States)

    Nabavi, Seyed Ali; Vladisavljević, Goran T; Gu, Sai; Manović, Vasilije

    2016-09-27

    Monodispersed microcapsules for gas capture and sensing were developed consisting of elastic semipermeable polymer shells of tunable size and thickness and pH-sensitive, gas selective liquid cores. The microcapsules were produced using glass capillary microfluidics and continuous on-the-fly photopolymerization. The inner fluid was 5-30 wt % K2CO3 solution with m-cresol purple, the middle fluid was a UV-curable liquid silicon rubber containing 0-2 wt % Dow Corning 749 fluid, and the outer fluid was aqueous solution containing 60-70 wt % glycerol and 0.5-2 wt % stabilizer (poly(vinyl alcohol), Tween 20, or Pluronic F-127). An analytical model was developed and validated for prediction of the morphology of the capsules under osmotic stress based on the shell properties and the osmolarity of the storage and core solutions. The minimum energy density and UV light irradiance needed to achieve complete shell polymerization were 2 J·cm(-2) and 13.8 mW·cm(-2), respectively. After UV exposure, the curing time for capsules containing 0.5 wt % Dow Corning 749 fluid in the middle phase was 30-40 min. The CO2 capture capacity of 30 wt % K2CO3 capsules was 1.6-2 mmol/g depending on the capsule size and shell thickness. A cavitation bubble was observed in the core when the internal water was abruptly removed by capillary suction, whereas a gradual evaporation of internal water led to buckling of the shell. The shell was characterized using TGA, DSC, and FTIR. The shell degradation temperature was 450-460 °C.

  11. Dense Gas in Nearby Galaxies: XVII. The Distribution of Ammonia in NGC253, Maffei2 and IC342

    CERN Document Server

    Lebron, M; Mauersberger, R; Henkel, C; Peck, A B; Menten, K M; Tarchi, A; Weiss, A

    2011-01-01

    The central few 100 pc of galaxies often contain large amounts of molecular gas. The chemical and physical properties of these extragalactic star formation regions differ from those in galactic disks, but are poorly constrained. This study aims to develop a better knowledge of the spatial distribution and kinetic temperature of the dense neutral gas associated with the nuclear regions of three prototypical spiral galaxies, NGC253, IC342, and Maffei2. VLA CnD and D configuration measurements have been made of three ammonia (NH3) inversion transitions. The (J,K)=(1,1) and (2,2) transitions of NH3 were imaged toward IC342 and Maffei2. The (3,3) transition was imaged toward NGC253. The entire flux obtained from single-antenna measurements is recovered for all three galaxies observed. Derived lower limits to the kinetic temperatures determined for the giant molecular clouds in the centers of these galaxies are between 25 and 50K. There is good agreement between the distributions of NH3 and other H2 tracers, such a...

  12. Removal of gas-phase ammonia and hydrogen sulfide using photocatalysis, nonthermal plasma, and combined plasma and photocatalysis at pilot scale.

    Science.gov (United States)

    Maxime, Guillerm; Amine, Assadi Aymen; Abdelkrim, Bouzaza; Dominique, Wolbert

    2014-11-01

    This study focuses on the removal of gas-phase ammonia (NH3) and hydrogen sulfide (H2S) in a continuous reactor. Photocatalysis and surface dielectric barrier discharge (SDBD) plasma are studied separately and combined. Though the removal of volatile organic compounds by coupling plasma and photocatalysis has been reported on a number of studies in laboratory scale, this is as far as we know the first time that it is used to remove inorganic malodorous pollutants. While each separate process is able to degrade ammonia and hydrogen sulfide, a synergetic effect appears when they are combined at a pilot scale, leading to removal capacity higher than the sum of each separate process. The removal capacity is higher when the gas circulates at a higher flow rate and when pollutant concentration is higher. The presence of water vapor in the gas is detrimental to the efficiency of the process. Operating conditions also influence the production of nitrogen oxides and ozone.

  13. Moisture effects on gas-phase biofilter ammonia removal efficiency, nitrous oxide generation, and microbial communities.

    Science.gov (United States)

    Yang, Liangcheng; Kent, Angela D; Wang, Xinlei; Funk, Ted L; Gates, Richard S; Zhang, Yuanhui

    2014-04-30

    We established a four-biofilter setup to examine the effects of moisture content (MC) on biofilter performance, including NH3 removal and N2O generation. We hypothesized that MC increase can improve NH3 removal, stimulate N2O generation and alter the composition and function of microbial communities. We found that NH3 removal efficiency was greatly improved when MC increased from 35 to 55%, but further increasing MC to 63% did not help much; while N2O concentration was low at 35-55% MC, but dramatically increased at 63% MC. Decreasing MC from 63 to 55% restored N2O concentration. Examination of amoA communities using T-RFLP and real-time qPCR showed that the composition and abundance of ammonia oxidizers were not significantly changed in a "moisture disturbance-disturbance relief" process in which MC was increased from 55 to 63% and then reduced to 55%. This observation supported the changes of NH3 removal efficiency. The composition of nosZ community was altered at 63% MC and then was recovered at 55% MC, which indicates resilience to moisture disturbance. The abundance of nosZ community was negatively correlated with moisture content in this process, and the decreased nosZ abundance at 63% MC explained the observation of increased N2O concentration at that condition. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Terahertz Active Photonic Crystals for Condensed Gas Sensing

    Directory of Open Access Journals (Sweden)

    Karl Unterrainer

    2011-06-01

    Full Text Available The terahertz (THz spectral region, covering frequencies from 1 to 10 THz, is highly interesting for chemical sensing. The energy of rotational and vibrational transitions of molecules lies within this frequency range. Therefore, chemical fingerprints can be derived, allowing for a simple detection scheme. Here, we present an optical sensor based on active photonic crystals (PhCs, i.e., the pillars are fabricated directly from an active THz quantum-cascade laser medium. The individual pillars are pumped electrically leading to laser emission at cryogenic temperatures. There is no need to couple light into the resonant structure because the PhC itself is used as the light source. An injected gas changes the resonance condition of the PhC and thereby the laser emission frequency. We achieve an experimental frequency shift of 10−3 times the center lasing frequency. The minimum detectable refractive index change is 1.6 × 10−5 RIU.

  15. Gas dependent sensing mechanism in ZnO nanobelt sensor

    Science.gov (United States)

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

    2017-02-01

    Gas sensing properties of ZnO nanobelts synthesized using carbothermal reduction method has been investigated. At room temperature (28 °C), the sensor films exhibit an appreciable response towards H2S and NO and response of these two gases were studied as a function of concentration. For NO the sensor films exhibit a complete reversible curve for the concentration range between 1 and 60 ppm. However, for H2S a complete recovery was obtained for concentration H2S exposure. After exposure, appearance of an additional peak at 26.6° corresponding to the formation of ZnS was observed in XRD. Formation of additional phase was further corroborated using the results of XPS. H2S exposure causes decrease in the intensity of O 1s peak and appearance of sulphide peaks at binding energies of 162.8 and 161.8 eV corresponding to S-2p peaks - 2p3/2 and 2p1/2, confirms the formation of ZnS upon exposure.

  16. Ammonia gas sensors based on In2O3/PANI hetero-nanofibers operating at room temperature.

    Science.gov (United States)

    Nie, Qingxin; Pang, Zengyuan; Lu, Hangyi; Cai, Yibing; Wei, Qufu

    2016-01-01

    Indium nitrate/polyvinyl pyrrolidone (In(NO3)3/PVP) composite nanofibers were synthesized via electrospinning, and then hollow structure indium oxide (In2O3) nanofibers were obtained through calcination with PVP as template material. In situ polymerization was used to prepare indium oxide/polyaniline (In2O3/PANI) composite nanofibers with different mass ratios of In2O3 to aniline. The structure and morphology of In(NO3)3/PVP, In2O3/PANI composite nanofibers and pure PANI were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and current-voltage (I-V) measurements. The gas sensing properties of these materials towards NH3 vapor (100 to 1000 ppm) were measured at room temperature. The results revealed that the gas sensing abilities of In2O3/PANI composite nanofibers were better than pure PANI. In addition, the mass ratio of In2O3 to aniline and the p-n heterostructure between In2O3 and PANI influences the sensing performance of the In2O3/PANI composite nanofibers. In this paper, In2O3/PANI composite nanofibers with a mass ratio of 1:2 exhibited the highest response values, excellent selectivity, good repeatability and reversibility.

  17. Ammonia gas sensors based on In2O3/PANI hetero-nanofibers operating at room temperature

    Directory of Open Access Journals (Sweden)

    Qingxin Nie

    2016-09-01

    Full Text Available Indium nitrate/polyvinyl pyrrolidone (In(NO33/PVP composite nanofibers were synthesized via electrospinning, and then hollow structure indium oxide (In2O3 nanofibers were obtained through calcination with PVP as template material. In situ polymerization was used to prepare indium oxide/polyaniline (In2O3/PANI composite nanofibers with different mass ratios of In2O3 to aniline. The structure and morphology of In(NO33/PVP, In2O3/PANI composite nanofibers and pure PANI were investigated by scanning electron microscopy (SEM, Fourier transform infrared spectroscopy (FTIR, X-ray diffraction (XRD, transmission electron microscopy (TEM and current–voltage (I–V measurements. The gas sensing properties of these materials towards NH3 vapor (100 to 1000 ppm were measured at room temperature. The results revealed that the gas sensing abilities of In2O3/PANI composite nanofibers were better than pure PANI. In addition, the mass ratio of In2O3 to aniline and the p–n heterostructure between In2O3 and PANI influences the sensing performance of the In2O3/PANI composite nanofibers. In this paper, In2O3/PANI composite nanofibers with a mass ratio of 1:2 exhibited the highest response values, excellent selectivity, good repeatability and reversibility.

  18. Fabrication, characterization and gas sensing properties of gold nanoparticle and calixarene multilayers

    Indian Academy of Sciences (India)

    IINCI ÇAPAN; ASEEL K HASSAN; RAJAA R ABBAS

    2017-02-01

    Calixarenes are a group of materials that are widely used for gas sensing studies because of their simple synthesis, conformational flexibility, binding group tunability, variability in their cavity sizes and improved selectivity to different gas molecules. In recent years it has been shown that incorporation of gold nanoparticles (AuNPs) into organic layers further enhances their gas sensing performance. The present study reports on the fabrication of thin films of calixarene and AuNPs using Langmuir–Schaefer (LS) methods. The gas sensing properties of the produced films are investigated on exposure to saturated vapours of volatile organic compounds (VOCs) using surface plasmon resonance as an optical detection technique. Multilayers comprising films of AuNPs and calixarene have been investigated to evaluate the effect of AuNPs on the films sensing performances. It has been demonstrated that the hybrid layers exhibited improved sensing performance in terms of the degree of their response.

  19. Modeling the sensing characteristics of chemi-resistive thin film semi-conducting gas sensors.

    Science.gov (United States)

    Ghosh, Abhishek; Majumder, S B

    2017-08-30

    For chemi-resistive thin film gas sensors a generic theoretical model is proposed to predict the variation of sensor response with the operating temperature and thickness of the sensing film. A diffusion equation is formulated assuming that inflammable target gases move through the sensing film by Knudsen diffusion and react with the adsorbed oxygen following first-order kinetics. We have assumed a realistic non-linear variation between the conductance and test gas concentration and derived a general expression relating the sensor response to the operating temperature and thickness of the film. Assuming Langmuir adsorption kinetics, we have theoretically predicted the response and recovery transients during gas sensing using thin film sensing elements. It is predicted that for irreversible type sensing, the response time is reduced with an increase in test gas concentration, whereas for reversible sensing, the response time is independent of test gas concentration. For zinc oxide thin film sensors, an excellent match is obtained between the model prediction and experimental data for their thickness (122 nm to 380 nm) and temperature variation (200 °C to 325 °C) in 500 ppm carbon monoxide (CO) sensing. The maximum CO response% (∼53%) was achieved in 320 nm thick ZnO films. The conductance transients for response and recovery for CO sensing closely follow Langmuir adsorption kinetics and as predicted theoretically, indeed for irreversible sensing, the response time reduces from 350 s to 220 s with an increase in test gas concentration from 20 to 550 ppm. In the case of reversible sensing we found that the response time is ∼55 s irrespective of the CO gas concentration in the range of 5-500 ppm. The models developed in the present work are quite generic in nature and we have discussed their applicability to a wide variety of sensing materials with various types of surface morphologies.

  20. Constraining U.S. ammonia emissions using TES remote sensing observations and the GEOS-Chem adjoint model

    Science.gov (United States)

    Ammonia (NH(3)has significant impacts on biodiversity, eutrophication, and acidification. Widespread uncertainty in the magnitude and seasonality of NH3 emissions hinders efforts to address these issues. In this work, we constrain U.S. NH3 sources using obse...

  1. Role of molar concentration in structural, optical and gas sensing performance of anatase phase TiO2 nanofilms: automated nebulizer spray pyrolysis (ANSP) technique

    Science.gov (United States)

    Gopala Krishnan, V.; Elango, P.; Ganesan, V.

    2017-07-01

    TiO2 nanofilms were deposited on a glass substrate at 500 °C using automated nebulizer spray pyrolysis. The anatase polycrystalline structure with increased grain size and variations of surfactant planes ( T c) were influenced by molar concentration on XRD study. AFM study shows the average roughness values were increased with increase in molar concentration. A granular domain like microstructure with crack and void-free particle was examined by FESEM. The maximum transmittance 95.5% (529.6 nm) for x = 0.05 M/L, further increment of molar concentration showed the decremented transmittance with red shift absorption edge and the calculated band gap values ( E g = 3.53-3.20 eV) also noted. The gas sensing performances of films were studied with respect to various gas sensing parameters and the ammonia (NH3) gas showed better sensing response ( S max = 89%) at 150 °C for 300 ppm gas concentration against other gases (C2H6O, CH4O, C3H8O and C3H6O).

  2. Effect of UV and vacuum treatment on stability of WO3 gas sensing films

    Science.gov (United States)

    Gao, Guohua; Wu, Guangming; Zhang, Zenghai; Wu, Jiandong; Feng, Wei; Shen, Jun; Zhang, Zhihua; Du, Ai

    2011-02-01

    UV and vacuum treatment, as well as annealing, were tried to recover the gas sensing property of WO3 films. Results show that gas sensing films can partially recover one or two coloring and bleaching cycles if kept in vacuum condition. And UV irradiation can well recover several cycles. But heat treatment does not show any obvious effect on the gas sensing recovery. Furthermore, IR and XPS spectra were used to identify the mechanism of this improvement. Results reveal that changes of water content will reduce the desorption energy of hydrogen atom, which will accelerate the bleaching velocity.

  3. Band alignment and depletion zone at ZnO/CdS and ZnO/CdSe hetero-structures for temperature independent ammonia vapor sensing.

    Science.gov (United States)

    Rajeswari Yogamalar, N; Sadhanandham, K; Chandra Bose, A; Jayavel, R

    2016-11-30

    An optical-fiber based evanescent ammonia vapor sensor was constructed with surface-passivated growth of zinc oxide (ZnO) nanostructures, which was achieved through a three-step wet chemical process. Initially, the ZnO nanostructures were synthesized using a wet-chemical method and subsequently surface-passivated with chalcogenide material compounds namely cadmium sulphide (CdS) and cadmium selenide (CdSe) nanoparticles individually using a citric acid assisted chemical synthesis technique. Finally, surface-passivated ZnO was deposited on the cladding modified optical-fiber using a dip coating process. X-ray diffraction (XRD), tunneling electron microscopy (TEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) analyses confirmed the growth of CdS and CdSe nanoparticles on the surface of ZnO nanoparticles. The atomic composition and the full width at half maximum (FWHM) of the oxygen O 1s oxidation state represented in the X-ray photoelectron spectra were lower and narrower for ZC2 nanostructures implying that the available surface oxygen had reacted well and promoted the uniform shell-like growth of CdSe nanoparticles on the ZnO. The significance of the surface-passivated ZnO was realized from UV-Vis diffuse reflectance spectroscopy (DRS) and a photo-luminescence (PL) study and was implemented in a room temperature optical-fiber based evanescent ammonia vapor sensor. The nano-sized CdS particles decorated on the surface of ZnO demonstrate a high vapor sensing behavior. The sensing enhancement was nearly 3 times larger than the core-shell like ZnO/CdSe (ZC2) nanostructures and was attributed to the effective interaction of the incident light and the sensing media, the change in the refractive index of the modified cladding regime, the rate of vapor adsorption and the effective charge-carrier transport between the so-formed hetero-junction interfaces. The ZC2 shows insignificant ammonia vapor adsorption and sensing due to decreased

  4. A pilot plant study for CO{sub 2} capture by aqueous ammonia applied to blast furnace gas in iron and steel making process

    Energy Technology Data Exchange (ETDEWEB)

    Young Kim, J.; Han, K.; Dong Chun, H. [CO2 Project, Research Inst. of Industrial Science and Technology, Pohang (Korea, Republic of)

    2009-07-01

    This presentation reported on a study in which carbon dioxide (CO{sub 2}) was captured from a demonstration iron and steel plant using low concentration aqueous ammonia as the absorbent chemical. The pilot plant was designed to process 50 Nm{sup 3}/h of blast furnace gas (BFG). The feed gas contained more than 20 per cent CO{sub 2} at 35 to 60 degrees C. Test runs revealed that the absorption efficiency of CO{sub 2} exceeded 80 per cent with a CO{sub 2} purity of more than 90 per cent in the product stream. The process parameters are currently being studied along with the various salts needed to prevent salt precipitation. It was determined that the use of waste heat recovery technology in the iron and steel-making process can render ammonia-based CO{sub 2} capture technology more economically feasible for the reduction of CO{sub 2}.

  5. Improved gas sensing and dielectric properties of Fe doped hydroxyapatite thick films: Effect of molar concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Mene, Ravindra U. [PDEA' s, Annasaheb Waghire College of Science, Arts and Commerce, Otur 412409, M.S. (India); School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, M.S. (India); Mahabole, Megha P. [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, M.S. (India); Mohite, K.C. [Haribhai. V. Desai College, Pune 411002, M.S. (India); Khairnar, Rajendra S., E-mail: rskhairnarsps@gmail.com [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, M.S. (India)

    2014-02-01

    Highlights: • We report improved gas sensing and dielectric characteristics of Fe ion exchanged HAp films. • Fe doped HAp film shows maximum gas response at relatively lower temperature. • Response and gas uptake capacity of sensors is improved for appropriate amount of Fe ions in HAp matrix. • Fe-HAp films exhibit remarkable improvement in dielectric properties compared to pure HAp. • Fe doped HAp films show significant improvement in gas sensing as well as in dielectric properties. - Abstract: In the present work Fe doped hydroxyapatite (Fe-HAp) thick films has been successfully utilized to improve the gas sensing as well as its dielectric properties. Initially, HAp nano powder is synthesized by chemical precipitation process and later on Fe ions are doped in HAp by ion exchange process. Structural and morphological modifications are observed by means of X-ray diffraction and scanning electron microscopy analysis. The sensing parameters such as operating temperature, response/recovery time and gas uptake capacity are experimentally determined. The Fe-HAp (0.05 M) film shows improved CO and CO{sub 2} gas sensing capacity at lower operating temperature compared to pure HAp. Moreover, variation of dielectric constant and dielectric loss for pure and Fe-HAp thick films are studied as a function of frequency in the range of 10 Hz–1 MHz. The study reveals that Fe doped HAp thick films improve the sensing and dielectric characteristics as compared to pure HAp.

  6. Hydrothermal synthesis of h-MoO{sub 3} microrods and their gas sensing properties to ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yueli; Yang, Shuang; Lu, Yu [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); Podval’naya, Natal’ya V. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Science, Ekaterinburg 620990 (Russian Federation); Chen, Wen, E-mail: chenw@whut.edu.cn [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); Zakharova, Galina S., E-mail: volkov@ihim.uran.ru [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Science, Ekaterinburg 620990 (Russian Federation)

    2015-12-30

    Highlights: • A simple hydrothermal acid-free method for the synthesis of h-MoO{sub 3} microrods with the hexagonal cross-section is reported. • The h-MoO{sub 3} phase is transformed to α-MoO{sub 3} at 439 °C. • The h-MoO{sub 3} microrods were employed to fabricate gas sensors to detect ethanol. • Sensor showed highest response with a sensitivity of 8.24–500 ppm C{sub 2}H{sub 5}OH at operating temperature of 332 °C. - Abstract: Hexagonal molybdenum trioxide (h-MoO{sub 3}) microrods were successfully synthesized via a novel and facile hydrothermal route from peroxomolybdate solution with the presence of NH{sub 4}Cl as the mineralizer. A variety of the techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry combined with the thermal gravimetric analysis (DSC–TG) were used to characterize the product. The gas sensing test indicates that h-MoO{sub 3} microrods have a good response to 5–500 ppm ethanol in the range of 273–380 °C, and the optimum operating temperature is 332 °C with a high sensitivity of 8.24 to 500 ppm ethanol. Moreover, it also has a good selectivity toward ethanol gas if compared with other gases, such as ammonia, methanol and toluene. The sensing mechanism of h-MoO{sub 3} microrods to ethanol was also discussed.

  7. Flexible High Energy Lidar Transmitter for Remote Gas and Wind Sensing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Fibertek proposes a high energy and flexible operation 1570 nm pulsed lidar transmitter for airborne and space-based remote CO2 gas and doppler wind sensing. The...

  8. Gas sensing properties of Cu and Cr activated BST thick films

    Indian Academy of Sciences (India)

    G H Jain; L A Patil

    2006-08-01

    H2S gas sensing properties of BST ((Ba0.67Sr0.33)TiO3) thick films are reported here for the first time. BST ceramic powder was prepared by mechanochemical process. Thick films of BST were prepared by screen-printing technique. The sensing performance of the films was tested for various gases. The films were surface customized by dipping them into aqueous solutions of CuCl2 and CrO3 for various intervals of time. These surface modified BST films showed improved sensitivity to H2S gas (100 ppm) than pure BST film. Chromium oxide was observed to be a better activator than copper oxide in H2S gas sensing. The effect of microstructure and amount of activators on H2S gas sensing were discussed. The sensitivity, selectivity, stability, response and recovery time of the sensor were measured and presented.

  9. Hydrothermal synthesis of self-assembled hierarchical tungsten oxides hollow spheres and their gas sensing properties.

    Science.gov (United States)

    Li, Jinwei; Liu, Xin; Cui, Jiashan; Sun, Jianbo

    2015-05-20

    Hierarchical self-assembled hollow spheres (HS) of tungsten oxide nanosheets have been synthesized via a template-free hydrothermal method. Morphology evolution of the products is determined by the amount of H2C2O4 (oxalic acid) which serves as chelating agent. Structural features of the products were characterized by X-ray diffraction (XRD), and morphology was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, the porous structure was analyzed using the Brunauer-Emmett-Teller (BET) approach. The synthesis mechanism of the products with self-assembled hierarchical structures was proposed. The NO2 gas sensing properties of self-assembled hierarchical WO3 HS materials were investigated, the gas sensing properties of WO3 synthesized by a variety of formulations were compared, and the possible gas sensing mechanism was discussed. The obvious enhancement of the gas sensing properties was ascribed to the structure of the hierarchical HS.

  10. Enhanced transduction of photonic crystal dye lasers for gas sensing via swelling polymer film

    DEFF Research Database (Denmark)

    Smith, Cameron; Lind, Johan Ulrik; Christiansen, Mads Brøkner;

    2011-01-01

    We present the enhanced transduction of a photonic crystal dye laser for gas sensing via deposition of an additional swelling polymer film. Device operation involves swelling of the polymer film during exposure to specific gases, leading to a change in total effective refractive index. Experimental...... in its application to other intracavity-based detection schemes to enable gas sensing. © 2011 Optical Society of America....

  11. Wireless gas sensing in South African underground platinum mines

    CSIR Research Space (South Africa)

    Abu-Mahfouz, Adnan M

    2014-04-01

    Full Text Available Approximately 70% of South African mines are classified as fiery, where methane gas potentially could cause explosions. The number of flammable gas reports and accidents are increasing steadily for both gold and platinum mines. However...

  12. Gas sensing properties of MWCNT layers electrochemically decorated with Au and Pd nanoparticles.

    Science.gov (United States)

    Dilonardo, Elena; Penza, Michele; Alvisi, Marco; Rossi, Riccardo; Cassano, Gennaro; Di Franco, Cinzia; Palmisano, Francesco; Torsi, Luisa; Cioffi, Nicola

    2017-01-01

    Multiwalled carbon nanotube (MWCNT)-based chemiresistors were electrochemically decorated with Au and Pd nanoparticles (NPs), resulting in an improvement in the detection of gaseous pollutants as compared to sensors based on pristine MWCNTs. Electrophoresis was used to decorate MWCNTs with preformed Au or Pd NPs, thus preserving their nanometer-sized dimensions and allowing the metal content to be tuned by simply varying the deposition time. The sensing response of unmodified and metal-decorated MWCNTs was evaluated towards different gaseous pollutants (e.g., NO2, H2S, NH3 and C4H10) at a wide range of concentrations in the operating temperature range of 45-200 °C. The gas sensing results were related to the presence, type and loading of metal NPs used in the MWCNT functionalization. Compared to pristine MWCNTs, metal-decorated MWCNTs revealed a higher gas sensitivity, a faster response, a better stability, reversibility and repeatability, and a low detection limit, where all of these sensing properties were controlled by the type and loading of the deposited metal catalytic NPs. Specifically, in the NO2 gas sensing experiments, MWCNTs decorated with the lowest Au content revealed the highest sensitivity at 150 °C, while MWCNTs with the highest Pd loading showed the highest sensitivity when operated at 100 °C. Finally, considering the reported gas sensing results, sensing mechanisms have been proposed, correlating the chemical composition and gas sensing responses.

  13. Versatile computer-controlled system for characterization of gas sensing materials.

    Science.gov (United States)

    Zhao, M; Huang, J X; Wong, M H; Tang, Y M; Ong, C W

    2011-10-01

    Design of a system used for characterizing gas sensing materials is described. It is distinctive of being able to measure electrical and optical responses of a sample simultaneously, control a number of measurement parameters, perform fast exchange of gaseous environment, and be fully controlled automatically. These features make the system to be versatile in determining most concerned performance indexes of a gas sensing material (e.g., sensitivity, stability, selectivity, response/recovery times, etc.) as functions of various combinations of measurement conditions (e.g., gas concentrations, temperature, total pressure, content of interferants, photo assist, relative humidity, soaking time in a fixed gas concentration, and number of switching cycles in a dynamic test, etc.). Rationales of the designs associated with general gas sensing mechanics are discussed.

  14. Structural properties and gas sensing behavior of sol-gel grown nanostructured zinc oxide

    Science.gov (United States)

    Rajyaguru, Bhargav; Gadani, Keval; Rathod, K. N.; Solanki, Sapana; Kansara, S. B.; Pandya, D. D.; Shah, N. A.; Solanki, P. S.

    2016-05-01

    In this communication, we report the results of the studies on structural properties and gas sensing behavior of nanostructured ZnO grown using acetone precursor based modified sol-gel technique. Final product of ZnO was sintered at different temperatures to vary the crystallite size while their structural properties have been studied using X-ray diffraction (XRD) measurement performed at room temperature. XRD results suggest the single phasic nature of all the samples and crystallite size increases from 11.53 to 20.96nm with increase in sintering temperature. Gas sensing behavior has been studied for acetone gas which indicates that lower sintered samples are more capable to sense the acetone gas and related mechanism has been discussed in the light of crystallite size, crystal boundary density, defect mechanism and possible chemical reaction between gas traces and various oxygen species.

  15. Au@ZnO nanostructures on porous silicon for photocatalysis and gas-sensing: the effect of plasmonic hot-electrons driven by visible-light

    Science.gov (United States)

    Zhou, Fang; Wang, Qiang; Liu, Wenjun

    2016-08-01

    Nanostructured heterojunctions play key role for transfer and separation of interfacial photo-carriers. At visible light illumination, the effects of Au nanoparticles (NPs) for the photocatalysis and gas-sensing performance of Au@ZnO nanstructures on porous silicon layer are reported. At optimized loading amount of Au NPs, the local surface plasmon resonance (LSPR) effect of Au NPs is studied. Generated by visible light irradiation, the LSPR effect of Au NPs promotes desorption and activation of surface adsorption oxygen species -{{{{O}}}2}-, which is initiated by hot electrons transfer through Au-ZnO nanojunctions. This mechanism is responsible for the enhanced photocatalysis of methyl orange molecular, as well as enhancing the detecting performance for ammonia (NH3) gas at room temperature.

  16. Gas sensing at the nanoscale: engineering SWCNT-ITO nano-heterojunctions for the selective detection of NH3 and NO2 target molecules

    Science.gov (United States)

    Rigoni, F.; Drera, G.; Pagliara, S.; Perghem, E.; Pintossi, C.; Goldoni, A.; Sangaletti, L.

    2017-01-01

    The gas response of single-wall carbon nanotubes (SWCNT) functionalized with indium tin oxide (ITO) nanoparticles (NP) has been studied at room temperature and an enhanced sensitivity to ammonia and nitrogen dioxide is demonstrated. The higher sensitivity in the functionalized sample is related to the creation of nano-heterojunctions at the interface between SWCNT bundles and ITO NP. Furthermore, the different response of the two devices upon NO2 exposure provides a way to enhance also the selectivity. This behavior is rationalized by considering a gas sensing mechanism based on the build-up of space-charge layers at the junctions. Finally, full recovery of the signal after exposure to NO2 is achieved by UV irradiation for the functionalized sample, where the ITO NP can play a role to hinder the poisoning effects on SWCNT due to NO2 chemisorption.

  17. Optical sensing elements for nitrogen dioxide (NO.sub.2) gas detection, a sol-gel method for making the sensing elements and fiber optic sensors incorporating nitrogen dioxide gas optical sensing elements

    Science.gov (United States)

    Mechery, Shelly John; Singh, Jagdish P.

    2007-07-03

    A sensing element, a method of making a sensing element, and a fiber optic sensor incorporating the sensing element are described. The sensor can be used for the quantitative detection of NO.sub.2 in a mixture of gases. The sensing element can be made by incorporating a diazotizing reagent which reacts with nitrous ions to produce a diazo compound and a coupling reagent which couples with the diazo compound to produce an azo dye into a sol and allowing the sol to form an optically transparent gel. The sensing element changes color in the presence of NO.sub.2 gas. The temporal response of the absorption spectrum at various NO.sub.2 concentrations has also been recorded and analyzed. Sensors having different design configurations are described. The sensing element can detect NO.sub.2 gas at levels of parts per billion.

  18. Design and development of a simple laboratory model to detect (15)N enrichment in cyanobacterial biomass and extra cellular ammonia using (15)N gas.

    Science.gov (United States)

    Selvakumar, G; Gopalaswamy, G; Arulmozhiselvan, K

    2007-03-01

    A laboratory scale working model that could detect the (15)N enrichment in cyanobacterial biomass and extracellular ammonia, using (15)N gas under in vitro conditions was designed and fabricated. Using the model, (15)N enrichment of 0.48% atom excess was detected in the cyanobacterial biomass on the 30 d after inoculation. The (15)N enrichment increased linearly in the extracellular ammoniacal fraction from the 20 d onward. The model would prove to be a useful tool to quantify the extent of (15)N enrichment under in vitro conditions using (15)N gas.

  19. Hydrogen gas sensing feature of polyaniline/titania (rutile) nanocomposite at environmental conditions

    Energy Technology Data Exchange (ETDEWEB)

    Milani Moghaddam, Hossain, E-mail: hossainmilani@yahoo.com [Solid State Physics Department, University of Mazandaran, Babolsar (Iran, Islamic Republic of); Nasirian, Shahruz [Solid State Physics Department, University of Mazandaran, Babolsar (Iran, Islamic Republic of); Basic Sciences Department, Mazandaran University of Science and Technology, Babol (Iran, Islamic Republic of)

    2014-10-30

    Graphical abstract: - Highlights: • Polyaniline/titania (rutile) nanocomposite (TPNC) was synthesized by a chemical oxidative polymerization method. • Surface morphology and titania (rutile) wt% in TPNC sensors were significant factors for H{sub 2} gas sensing. • TPNC sensors could be used for H{sub 2} gas sensing at different R.H. humidity. • TPNC Sensors exhibited considerable sensitive, reversible and repeatable response to H{sub 2} gas at environmental conditions. - Abstract: The resistance-based sensors of polyaniline/titania (rutile) nanocomposite (TPNC) were prepared by spin coating technique onto an epoxy glass substrate with Cu-interdigited electrodes to study their hydrogen (H{sub 2}) gas sensing features. Our findings are that the change of the surface morphology, porosity and wt% of titania in TPNCs have a significant effect on H{sub 2} gas sensing of sensors. All of the sensors had a reproducibility response toward 0.8 vol% H{sub 2} gas at room temperature, air pressure and 50% relative humidity. A sensor with 40 wt% of titania nanoparticles had better response/recovery time and the response than other sensors. Moreover, H{sub 2} gas sensing mechanism of TPNC sensors based contact areas and the correlation of energy levels between PANI chains and the titania grains were studied.

  20. Influence of gas-particle partitioning on ammonia and nitric acid fluxes above a deciduous forest in the Midwestern USA

    Science.gov (United States)

    Hansen, K.; Sørensen, L. L.; Hornsby, K. E.; Boegh, E.; Pryor, S. C.

    2013-12-01

    Quantifying the atmosphere-biosphere exchange of reactive nitrogen gasses (including ammonia (NH3) and nitric acid (HNO3)) is crucial to assessing the impact of anthropogenic activities on natural and semi-natural ecosystems. However, measuring the deposition of reactive nitrogen is challenging due to bi-directionality of the flux, and the dynamics of the chemical gas/aerosol equilibrium of NH3 and HNO3 (or other atmospheric acids) with aerosol-phase ammonium (NH4+) and nitrate (NO3-). NH3 and HNO3 are both very reactive and typically exhibit higher deposition velocities than aerosol NH4+. Therefore, the phase partitioning between gas and aerosol phases can have a significant effect on local budgets and atmospheric transport distances (Nemitz et al., Atmos. Chem. Phys., 2004). In this study, fluxes of NH3, HNO3 and carbon dioxide (CO2) along with size-resolved N-aerosol concentrations are measured above the deciduous forest, Morgan Monroe State Forest (MMSF) in south-central Indiana (39°53'N, 86°25'W) during a field campaign. Two relaxed eddy accumulation (REA) systems are used to measure fluxes and concentrations of NH3 and HNO3 at 44 m. The NH3 REA system operates based on wet effluent diffusion denuders with detection by florescence and half-hourly flux measurements are calculated. HNO3 REA system is based on gas capture on sodium chloride (NaCl) coated denuders with subsequent analysis by ion-chromatography, and the resulting fluxes have a resolution of 3-4 hours. CO2 fluxes are measured by eddy covariance using a closed-path Licor LI-7500, while two MSP MOUDI-110 impactors are used to measure the 24-hourly average inorganic and 48 hourly averaged organic ion concentrations in 11 size bins, respectively, just above the canopy level (28 m). The results of this field campaign are used to quantify the fluxes of NH3, HNO3, CO2 to/from the forest during the transition towards senescence, and to investigate process-level controls (e.g. the role of phase

  1. Thin SnOx films for surface plasmon resonance enhanced ellipsometric gas sensing (SPREE).

    Science.gov (United States)

    Fischer, Daniel; Hertwig, Andreas; Beck, Uwe; Lohse, Volkmar; Negendank, Detlef; Kormunda, Martin; Esser, Norbert

    2017-01-01

    Background: Gas sensors are very important in several fields like gas monitoring, safety and environmental applications. In this approach, a new gas sensing concept is investigated which combines the powerful adsorption probability of metal oxide conductive sensors (MOS) with an optical ellipsometric readout. This concept shows promising results to solve the problems of cross sensitivity of the MOS concept. Results: Undoped tin oxide (SnOx) and iron doped tin oxide (Fe:SnOx) thin add-on films were prepared by magnetron sputtering on the top of the actual surface plasmon resonance (SPR) sensing gold layer. The films were tested for their sensitivity to several gas species in the surface plasmon resonance enhanced (SPREE) gas measurement. It was found that the undoped tin oxide (SnOx) shows higher sensitivities to propane (C3H8) then to carbon monoxide (CO). By using Fe:SnOx, this relation is inverted. This behavior was explained by a change of the amount of binding sites for CO in the layer due to this iron doping. For hydrogen (H2) no such relation was found but the sensing ability was identical for both layer materials. This observation was related to a different sensing mechanism for H2 which is driven by the diffusion into the layer instead of adsorption on the surface. Conclusion: The gas sensing selectivity can be enhanced by tuning the properties of the thin film overcoating. A relation of the binding sites in the doped and undoped SnOx films and the gas sensing abilities for CO and C3H8 was found. This could open the path for optimized gas sensing devices with different coated SPREE sensors.

  2. Examination of charge transfer in Au/YSZ for high-temperature optical gas sensing

    Energy Technology Data Exchange (ETDEWEB)

    Baltrus, John P. [U.S. DOE; Ohodnicki, Paul R. [U.S. DOE

    2014-01-01

    Au-nanoparticle incorporated oxide thin film materials demonstrate significant promise as functionalsensor materials for high temperature optical gas sensing in severe environments relevant for fossil andnuclear based power generation. The Au/yttria-stabilized zirconia (YSZ) system has been extensivelystudied in the literature and serves as a model system for fundamental investigations that seek to betterunderstand the mechanistic origin of the plasmonic gas sensing response. In this work, X-ray photoelec-tron spectroscopy techniques are applied to Au/YSZ films in an attempt to provide further experimentalevidence for a proposed sensing mechanism involving a change in free carrier density of Au nanoparticles due to charge transfer.

  3. An exploration on greenhouse gas and ammonia production by insect species suitable for animal or human consumption.

    Directory of Open Access Journals (Sweden)

    Dennis G A B Oonincx

    Full Text Available BACKGROUND: Greenhouse gas (GHG production, as a cause of climate change, is considered as one of the biggest problems society is currently facing. The livestock sector is one of the large contributors of anthropogenic GHG emissions. Also, large amounts of ammonia (NH(3, leading to soil nitrification and acidification, are produced by livestock. Therefore other sources of animal protein, like edible insects, are currently being considered. METHODOLOGY/PRINCIPAL FINDINGS: An experiment was conducted to quantify production of carbon dioxide (CO₂ and average daily gain (ADG as a measure of feed conversion efficiency, and to quantify the production of the greenhouse gases methane (CH₄ and nitrous oxide (N₂O as well as NH₃ by five insect species of which the first three are considered edible: Tenebrio molitor, Acheta domesticus, Locusta migratoria, Pachnoda marginata, and Blaptica dubia. Large differences were found among the species regarding their production of CO₂ and GHGs. The insects in this study had a higher relative growth rate and emitted comparable or lower amounts of GHG than described in literature for pigs and much lower amounts of GHG than cattle. The same was true for CO₂ production per kg of metabolic weight and per kg of mass gain. Furthermore, also the production of NH₃ by insects was lower than for conventional livestock. CONCLUSIONS/SIGNIFICANCE: This study therefore indicates that insects could serve as a more environmentally friendly alternative for the production of animal protein with respect to GHG and NH₃ emissions. The results of this study can be used as basic information to compare the production of insects with conventional livestock by means of a life cycle analysis.

  4. Effect of Alum Additions to Poultry Litter on In-House Ammonia and Greenhouse Gas Concentrations and Emissions.

    Science.gov (United States)

    Eugene, Branly; Moore, Philip A; Li, Hong; Miles, Dana; Trabue, Steven; Burns, Robert; Buser, Michael

    2015-09-01

    Alum [Al(SO4) ·14HO] addition to poultry litter has been shown to reduce ammonia (NH) concentrations in poultry houses; however, its effects on greenhouse gas (GHG; NO, CH, and CO) emissions is unknown. The objectives of this study were to determine the effects of alum additions on (i) in-house NH and GHG concentrations, (ii) NH and GHG emissions, and (iii) litter chemical properties. Two identical broiler houses located in northwest Arkansas were used for this study: one house was a control and the other was treated with alum between each flock of birds. Ventilation rates were coupled with in-house NH and GHG measurements to determine emission rates. Overall, alum additions significantly reduced the daily average in-house NH concentration by 42% (8.9 vs. 15.4 μL L), and the overall NH emission rate was reduced by 47% (7.2 vs. 13.4 kg d house). The average cumulative NH emission for the three flocks was 330 kg house flock for the alum-treated house and 617 kg house flock for the control. Concentrations and emissions of nitrous oxide (NO) and methane (CH) from the alum-treated house were not significantly different than the untreated house. However, carbon dioxide (CO) emissions were significantly higher from the untreated house than the alum-treated house. Alum also significantly increased litter N content and reduced the C/N ratio. These results indicate that the addition of alum to poultry litter is not only an effective management practice for reducing in-house NH concentrations and emissions but also significantly reduces CO emissions from poultry facilities.

  5. Measurement of gas-phase ammonia and amines in air by collection onto an ion exchange resin and analysis by ion chromatography

    Directory of Open Access Journals (Sweden)

    M. L. Dawson

    2014-02-01

    Full Text Available Ammonia and amines are common trace gases in the atmosphere and have a variety of both biogenic and anthropogenic sources, with a major contribution coming from agricultural sites. In addition to their malodorous nature, both ammonia and amines have been shown to enhance particle formation from acids such as nitric, sulfuric and methanesulfonic acids, which has implications for visibility, human health and climate. A key component of quantifying the effects of these species on particle formation is accurate gas-phase measurements in both laboratory and field studies. However, these species are notoriously difficult to measure as they are readily taken up on surfaces, including onto glass surfaces from aqueous solution as established in the present studies. We describe here a novel technique for measuring gas-phase ammonia and amines that involves uptake onto a weak cation exchange resin followed by extraction and analysis using ion chromatography. Two variants, one for ppb concentrations in air and the second with lower (ppt detection limits, are described. The latter involves the use of a custom-designed high-pressure cartridge to hold the resin for in-line extraction. These methods avoid the use of sampling lines, which can lead to significant inlet losses of these compounds. They also have the advantages of being relatively simple and inexpensive. The applicability of this technique to ambient air is demonstrated in measurements made near a cattle farm in Chino, CA.

  6. Measurement of gas-phase ammonia and amines in air by collection onto an ion exchange resin and analysis by ion chromatography

    Science.gov (United States)

    Dawson, M. L.; Perraud, V.; Gomez, A.; Arquero, K. D.; Ezell, M. J.; Finlayson-Pitts, B. J.

    2014-08-01

    Ammonia and amines are common trace gases in the atmosphere and have a variety of both biogenic and anthropogenic sources, with a major contribution coming from agricultural sites. In addition to their malodorous nature, both ammonia and amines have been shown to enhance particle formation from acids such as nitric, sulfuric and methanesulfonic acids, which has implications for visibility, human health and climate. A key component of quantifying the effects of these species on particle formation is accurate gas-phase measurements in both laboratory and field studies. However, these species are notoriously difficult to measure as they are readily taken up on surfaces, including onto glass surfaces from aqueous solution as established in the present studies. We describe here a novel technique for measuring gas-phase ammonia and amines that involves uptake onto a weak cation exchange resin followed by extraction and analysis using ion chromatography. Two variants - one for parts per billion concentrations in air and the second with lower (parts per trillion) detection limits - are described. The latter involves the use of a custom-designed high-pressure cartridge to hold the resin for in-line extraction. These methods avoid the use of sampling lines, which can lead to significant inlet losses of these compounds. They also have the advantages of being relatively simple and inexpensive. The applicability of this technique to ambient air is demonstrated in measurements made near a cattle farm in Chino, CA.

  7. Quantum dots as mediators in gas sensing: A case study of CdS sensitized WO3 sensing composites

    Science.gov (United States)

    Concina, Isabella; Comini, Elisabetta; Kaciulis, Saulius; Sberveglieri, Giorgio

    2014-01-01

    In this study the proof of principle of the use of naked semiconductor directly generated on metal oxide surface as mediators in gas sensing is provided. Successive ionic layer absorption and reaction (SILAR) technique has been applied to sensitize a WO3 thin film with CdS quantum dots. Response to gases of bare WO3 is deeply modified: quantum dots dramatically increase the metal oxide conductance, otherwise rather poor, and modify the capability of detecting environmental pollutants, such as CO and NO2. A modified sensing mechanism is proposed to rationalize the mediation exerted by the semiconducting active layer on the interaction between gaseous species and WO3 surface.

  8. Chemochromic Detector for Sensing Gas Leakage and Process for Producing the Same

    Science.gov (United States)

    Roberson, Luke B. (Inventor); Captain, Janine E. (Inventor); Williams, Martha K. (Inventor); Tate, LaNetra Clayton (Inventor)

    2015-01-01

    A chemochromic sensor for detecting a combustible gas, such as hydrogen, includes a chemochromic pigment and a textile polymer. The textile material includes a chemochromic pigment operably responsive to a combustible gas. The combustible gas sensing textile material can be made by melt spinning, solution spinning, or other similar techniques. In a preferred embodiment carbon nanotubes are used with the textile material which will increase the material strength and alter the thermal and/or electrical properties. These textiles woven into fabrics can provide garments not only with hydrogen sensing capabilities but the carbon nanotubes will allow for a range of sensing capabilities to be embedded (i.e. gas, health, and electronic monitors) within the garments.

  9. Photoluminescent Metal–Organic Frameworks for Gas Sensing

    Science.gov (United States)

    Lin, Rui‐Biao; Liu, Si‐Yang; Ye, Jia‐Wen; Li, Xu‐Yu

    2016-01-01

    Luminescence of porous coordination polymers (PCPs) or metal–organic frameworks (MOFs) is sensitive to the type and concentration of chemical species in the surrounding environment, because these materials combine the advantages of the highly regular porous structures and various luminescence mechanisms, as well as diversified host‐guest interactions. In the past few years, luminescent MOFs have attracted more and more attention for chemical sensing of gas‐phase analytes, including common gases and vapors of solids/liquids. While liquid‐phase and gas‐phase luminescence sensing by MOFs share similar mechanisms such as host‐guest electron and/or energy transfer, exiplex formation, and guest‐perturbing of excited‐state energy level and radiation pathways, via various types of host‐guest interactions, gas‐phase sensing has its unique advantages and challenges, such as easy utilization of encapsulated guest luminophores and difficulty for accurate measurement of the intensity change. This review summarizes recent progresses by using luminescent MOFs as reusable sensing materials for detection of gases and vapors of solids/liquids especially for O2, highlighting various strategies for improving the sensitivity, selectivity, stability, and accuracy, reducing the materials cost, and developing related devices.

  10. Silicon nanowire-based devices for gas-phase sensing

    NARCIS (Netherlands)

    Cao, A.; Sudhölter, E.J.R.; De Smet, L.C.P.M.

    2013-01-01

    Since their introduction in 2001, SiNW-based sensor devices have attracted considerable interest as a general platform for ultra-sensitive, electrical detection of biological and chemical species. Most studies focus on detecting, sensing and monitoring analytes in aqueous solution, but the number of

  11. Determination Of Gas Mixture Components Using Fluctuation Enhanced Sensing And The LS-SVM Regression Algorithm

    Directory of Open Access Journals (Sweden)

    Lentka Łukasz

    2015-09-01

    Full Text Available This paper analyses the effectiveness of determining gas concentrations by using a prototype WO3 resistive gas sensor together with fluctuation enhanced sensing. We have earlier demonstrated that this method can determine the composition of a gas mixture by using only a single sensor. In the present study, we apply Least-Squares Support-Vector-Machine-based (LS-SVM-based nonlinear regression to determine the gas concentration of each constituent in a mixture. We confirmed that the accuracy of the estimated gas concentration could be significantly improved by applying temperature change and ultraviolet irradiation of the WO3 layer. Fluctuation-enhanced sensing allowed us to predict the concentration of both component gases.

  12. Highly Sensitive Capacitive Gas Sensing at Ionic Liquid-Electrode Interfaces.

    Science.gov (United States)

    Wang, Zhe; Guo, Min; Mu, Xiaoyi; Sen, Soumyo; Insley, Thomas; Mason, Andrew J; Král, Petr; Zeng, Xiangqun

    2016-02-01

    We have developed an ultrasensitive gas-detection method based on the measurement of a differential capacitance of electrified ionic liquid (IL) electrode interfaces in the presence and absence of adsorbed gas molecules. The observed change of differential capacitance has a local maximum at a certain potential that is unique for each type of gas, and its amplitude is related to the concentration of the gas molecules. We establish and validate this gas-sensing method by characterizing SO2 detection at ppb levels with less than 1.8% signal from other interfering species (i.e., CO2, O2, NO2, NO, SO2, H2O, H2, and cyclohexane, tested at the same concentration as SO2). This study opens a new avenue of utilizing tunable electrified IL-electrode interfaces for selective sensing of molecules with a kinetic size resolution of 0.1 Å.

  13. Fabrication of Cubic p-n Heterojunction-Like NiO/In2O3 Composite Microparticles and Their Enhanced Gas Sensing Characteristics

    Directory of Open Access Journals (Sweden)

    Hou Xuemei

    2016-01-01

    Full Text Available Oxide semiconductor In2O3 has been extensively used as a gas sensing material for the detection of various toxic gases. However, the pure In2O3 sensor is always suffering from its low sensitivity. In the present study, a dramatic enhancement of sensing characteristic of cubic In2O3 was achieved by deliberately fabricating p-n heterojunction-like NiO/In2O3 composite microparticles as sensor material. The NiO-decorated In2O3 p-n heterojunction-like sensors were prepared through the hydrothermal transformation method. The as-synthesized products were characterized using SEM-EDS, XRD, and FT-IR, and their gas sensing characteristics were investigated by detecting the gas response. The experimental results showed that the response of the NiO/In2O3 sensors to 600 ppm methanal was 85.5 at 260°C, revealing a dramatic enhancement over the pure In2O3 cubes (21.1 at 260°C. Further, a selective detection of methanol with inappreciable cross-response to other gases, like formaldehyde, benzene, methylbenzene, trichloromethane, ethanol, and ammonia, was achieved. The cause for the enhanced gas response was discussed in detailed. In view of the facile method of fabrication of such composite sensors and the superior gas response performance of samples, the cubic p-n heterojunction-like NiO/In2O3 sensors present to be a promising and viable strategy for the detection of indoor air pollution.

  14. Parameter Optimization on Experimental Study to Reduce Ammonia Escape in CO2 Absorption by Ammonia Scrubbing

    Institute of Scientific and Technical Information of China (English)

    Hao Leng; Jianmin Gao; Mingyue He; Min Xie; Qian Du; Rui Sun; Shaohua Wu

    2016-01-01

    In order to research ammonia escape in CO2 absorption by ammonia scrubbing, ammonia escape was studied in CO2 absorption process using the bubbling reactor in different conditions as gas flow rate, CO2 ratio, absorbent temperature and ammonia concentration and quantity of escaped ammonia was measured by chemical titration. The results indicated that, the amount of ammonia escape can be around 20% of original amount in 90 min and the escaped amount will increase with the rise of gas flow rate, absorbent temperature, concentration of ammonia while decrease as CO2 ratio goes up. Through the analysis of the law of ammonia escape, at the same time, combined with ammonia escape and the influence of the relationship between the CO2 absorption efficiency, reducing ammonia escape working condition parameter optimization is given.

  15. Fiber Bragg grating-based wavelength modulation spectroscopy technique for trace gas sensing

    Science.gov (United States)

    Tiwari, Shivani; Vasa, Nilesh J.; Srinivasan, Balaji

    2016-04-01

    A novel gas sensing system based on a tunable fiber Bragg grating (FBG) and a Super luminescent light emitting diode (SLED) source is proposed for trace gas sensing. Such a system has been demonstrated for precise detection of acetylene (C2H2) using wavelength modulation spectroscopy technique (WMS) based on modulating the Bragg wavelength of FBG within the width of an absorption line of a target gas. The sensing system has been calibrated against specific gas concentrations (ppm) through controlled experiments and the minimum detectable acetylene (C2H2) gas concentration is experimentally found to be 80 ppm (0.008% by volume). Furthermore, the detection limit of the system is estimated to be limited by the noise floor of our system at 7 ppm (0.0007% by volume). The proposed system provides a relatively inexpensive alternative for trace gas sensing based on a well-established FBG technology. Moreover, the proposed system has tremendous potential for simultaneous detection of multiple species through the use of a cascaded set of carefully chosen FBGs.

  16. Gas-Tolerant Device Senses Electrical Conductivity of Liquid

    Science.gov (United States)

    O'Connor, Edward W.

    2005-01-01

    The figure depicts a device for measuring the electrical conductivity of a flowing liquid. Unlike prior such devices, this one does not trap gas bubbles entrained in the liquid. Usually, the electrical conductivity of a liquid is measured by use of two electrodes immersed in the liquid. A typical prior device based on this concept contains large cavities that can trap gas. Any gas present between or near the electrodes causes a significant offset in the conductivity reading and, if the gas becomes trapped, then the offset persists. Extensive tests on two-phase (liquid/ gas) flow have shown that in the case of liquid flowing along a section of tubing, gas entrained in the liquid is not trapped in the section as long as the inner wall of the section is smooth and continuous, and the section is the narrowest tubing section along the flow path. The design of the device is based on the foregoing observation: The electrodes and the insulators separating the electrodes constitute adjacent parts of the walls of a tube. The bore of the tube is machined to make the wall smooth and to provide a straight flow path from the inlet to the outlet. The diameter of the electrode/insulator tube assembly is less than the diameter of the inlet or outlet tubing. An outer shell contains the electrodes and insulators and constitutes a leak and pressure barrier. Any gas bubble flowing through this device causes only a momentary conductivity offset that is filtered out by software used to process the conductivity readings.

  17. First detection of gas-phase ammonia in a planet-forming disk. NH3, N2H+, and H2O in the disk around TW Hydrae

    Science.gov (United States)

    Salinas, Vachail N.; Hogerheijde, Michiel R.; Bergin, Edwin A.; Cleeves, L. Ilsedore; Brinch, Christian; Blake, Geoffrey A.; Lis, Dariusz C.; Melnick, Gary J.; Panić, Olja; Pearson, John C.; Kristensen, Lars; Yıldız, Umut A.; van Dishoeck, Ewine F.

    2016-06-01

    Context. Nitrogen chemistry in protoplanetary disks and the freeze-out on dust particles is key for understanding the formation of nitrogen-bearing species in early solar system analogs. In dense cores, 10% to 20% of the nitrogen reservoir is locked up in ices such as NH3, NH4+ and OCN-. So far, ammonia has not been detected beyond the snowline in protoplanetary disks. Aims: We aim to find gas-phase ammonia in a protoplanetary disk and characterize its abundance with respect to water vapor. Methods: Using HIFI on the Herschel Space Observatory, we detected for the first time the ground-state rotational emission of ortho-NH3 in a protoplanetary disk around TW Hya. We used detailed models of the disk's physical structure and the chemistry of ammonia and water to infer the amounts of gas-phase molecules of these species. We explored two radial distributions (extended across the disk and confined to distributions (near the midplane and at intermediate heights above the midplane, where water is expected to photodesorb off icy grains) to describe the (unknown) location of the molecules. These distributions capture the effects of radial drift and vertical settling of ice-covered grains. Results: The NH310-00 line is detected simultaneously with H2O 110-101 at an antenna temperature of 15.3 mK in the Herschel beam; the same spectrum also contains the N2H+ 6-5 line with a strength of 18.1 mK. We use physical-chemical models to reproduce the fluxes and assume that water and ammonia are cospatial. We infer ammonia gas-phase masses of 0.7-11.0 × 1021 g, depending on the adopted spatial distribution, in line with previous literature estimates. For water, we infer gas-phase masses of 0.2-16.0 × 1022 g, improving upon earlier literature estimates This corresponds to NH3/H2O abundance ratios of 7%-84%, assuming that water and ammonia are co-located. The inferred N2H+ gas mass of 4.9 × 1021 g agrees well with earlier literature estimates that were based on lower excitation

  18. Phase Noise Squeezing Based Parametric Bifurcation Tracking of MIP-Coated Microbeam MEMS Sensor for TNT Explosive Gas Sensing

    Science.gov (United States)

    2014-06-08

    Based Parametric Bifurcation Tracking of Mip -Coated Microbeam MEMS Sensor for TNT Explosive Gas Sensing See Attached The views, opinions and/or...2050 1 ABSTRACT Phase Noise-Squeezing-Based Parametric Bifurcation Tracking of Mip -Coated Microbeam MEMS Sensor for TNT Explosive Gas Sensing...SQUEEZING BASED PARAMETRIC BIFURCATION TRACKING OF MIP -COATED MICROBEAM MEMS SENSOR FOR TNT EXPLOSIVE GAS SENSING L. L. Li1*, E. L. Holthoff2, L. A

  19. Synthesis Methods, Microscopy Characterization and Device Integration of Nanoscale Metal Oxide Semiconductors for Gas Sensing

    Directory of Open Access Journals (Sweden)

    Randy L. Vander Wal

    2009-09-01

    Full Text Available A comparison is made between SnO2, ZnO, and TiO2 single-crystal nanowires and SnO2 polycrystalline nanofibers for gas sensing. Both nanostructures possess a one-dimensional morphology. Different synthesis methods are used to produce these materials: thermal evaporation-condensation (TEC, controlled oxidation, and electrospinning. Advantages and limitations of each technique are listed. Practical issues associated with harvesting, purification, and integration of these materials into sensing devices are detailed. For comparison to the nascent form, these sensing materials are surface coated with Pd and Pt nanoparticles. Gas sensing tests, with respect to H2, are conducted at ambient and elevated temperatures. Comparative normalized responses and time constants for the catalyst and noncatalyst systems provide a basis for identification of the superior metal-oxide nanostructure and catalyst combination. With temperature-dependent data, Arrhenius analyses are made to determine activation energies for the catalyst-assisted systems.

  20. Synthesis of ZnO nanosheet arrays with exposed (100) facets for gas sensing applications.

    Science.gov (United States)

    Xiao, Chuanhai; Yang, Tianye; Chuai, Mingyan; Xiao, Bingxin; Zhang, Mingzhe

    2016-01-01

    ZnO nanosheet (NS) arrays have been synthesized by a facile ultrathin liquid layer electrodeposition method. The ion concentration and electrode potential play important roles in the formation of ZnO NS arrays. Studies on the structural information indicate that the NSs are exposed with (100) facets. The results of Raman and PL spectra indicate that there existed a large amount of oxygen vacancies in the NSs. The gas sensing performances of the ZnO NS arrays are investigated: the ZnO NS arrays exhibited high gas selectivity and quick response/recovery for detecting NO2 at a low working temperature. High binding energies between NO2 molecules and exposed ZnO(100) facets lead to large surface reconstructions, which is responsible for the intrinsic NO2 sensing properties. In addition, the highly exposed surface and a large amount of oxygen vacancies existing in the NSs also make a great contribution to the gas sensing performance.

  1. Correlating defect induced ferromagnetism and gas sensing properties of undoped tin oxide sensors

    Science.gov (United States)

    Kamble, Vinayak B.; Umarji, Arun M.

    2014-06-01

    A correlation between gas sensing properties and defect induced Room Temperature Ferromagnetism (RTFM) is demonstrated in non-stoichiometric SnO2 prepared by solution combustion method. The presence of oxygen vacancies (VO), confirmed by RTFM is identified as the primary factor for enhanced gas sensing effect. The as-prepared SnO2 shows high saturation magnetization of ˜0.018 emu/g as compared to ˜0.002 and ˜0.0005 emu/g in annealed samples and SnO2 prepared by precipitation respectively. The SnO2 prepared by precipitation which is an equilibrium method of synthesis shows lesser defects compared to the combustion product and hence exhibits lesser sensitivity in spite of smaller crystallite size. The study utilizes RTFM as a potential tool to characterize metal oxide gas sensors and recognizes the significance of oxygen vacancies in sensing mechanism over the microstructure.

  2. 回收合成氨尾气副产液化天然气工艺技术%Process Technology of Producing Byproduct Liquefied Natural Gas from Recovery of Ammonia Tail Gas

    Institute of Scientific and Technical Information of China (English)

    王辉

    2015-01-01

    A description is given of the selection of process schemes liquefying and separating methane from ammonia vent gas and purge gas from ammonia tank to produce liquefied natural gas, and the economic benefit of the project is analyzed.After constructed and put into operation of the project,the annual sales revenue is 21.456 million yuan,and the annual new profit is 4.972 million yuan,which has significance to the transformation of traditional ammonia industry chain.%介绍了氨合成放空气和氨罐弛放气中甲烷液化分离制液化天然气的工艺方案选择,分析了该项目的经济效益。该项目建成投产后,年销售收入2145.60万元,每年可新增利润497.20万元,对改造传统的合成氨产业链具有重要意义。

  3. The CRIRES Search for Planets Around the Lowest-Mass Stars. I. High-Precision Near-Infrared Radial Velocities with an Ammonia Gas Cell

    CERN Document Server

    Bean, Jacob L; Hartman, Henrik; Nilsson, Hampus; Wiedemann, Guenter; Reiners, Ansgar; Dreizler, Stefan; Henry, Todd J

    2009-01-01

    Radial velocities measured from near-infrared spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that yields near-infrared radial velocity precision comparable to that which is routinely obtained in the visible. We describe a method for measuring high-precision relative radial velocities of cool stars from K-band spectra. The method makes use of a glass cell filled with ammonia gas to calibrate the spectrograph response similar to the iodine cell technique that has been used so successfully in the visible. Stellar spectra are obtained through the ammonia cell and modeled as the product of a Doppler-shifted template spectrum of the object and a spectrum of the cell, convolved with a variable instrumental profile model. A complicating factor is that a significant number of telluric absorption lines are present in the spectral regions containing useful stellar and ammonia lines. The telluric lines are modeled simultaneou...

  4. Improvement of activated carbons as oxygen reduction catalysts in neutral solutions by ammonia gas treatment and their performance in microbial fuel cells

    KAUST Repository

    Watson, Valerie J.

    2013-11-01

    Commercially available activated carbon (AC) powders from different precursor materials (peat, coconut shell, coal, and hardwood) were treated with ammonia gas at 700 C to improve their performance as oxygen reduction catalysts in neutral pH solutions used in microbial fuel cells (MFCs). The ammonia treated ACs exhibited better catalytic performance in rotating ring-disk electrode tests than their untreated precursors, with the bituminous based AC most improved, with an onset potential of Eonset = 0.12 V (untreated, Eonset = 0.08 V) and n = 3.9 electrons transferred in oxygen reduction (untreated, n = 3.6), and the hardwood based AC (treated, E onset = 0.03 V, n = 3.3; untreated, Eonset = -0.04 V, n = 3.0). Ammonia treatment decreased oxygen content by 29-58%, increased nitrogen content to 1.8 atomic %, and increased the basicity of the bituminous, peat, and hardwood ACs. The treated coal based AC cathodes had higher maximum power densities in MFCs (2450 ± 40 mW m-2) than the other AC cathodes or a Pt/C cathode (2100 ± 1 mW m-2). These results show that reduced oxygen abundance and increased nitrogen functionalities on the AC surface can increase catalytic performance for oxygen reduction in neutral media. © 2013 Elsevier B.V. All rights reserved.

  5. Detection of Gas Slugs in Heat Pipes

    Science.gov (United States)

    Jones, J. A.

    1985-01-01

    Temperature sensing system detects presence of gas slugs in heat pipes. System designed for operation between zero and 70 degrees C and detects noncondensable pockets of gas that result from decomposition of ammonia cooling fluid. Slugs 1 in. (25mm) in length detected.

  6. Combustion driven ammonia generation strategies for passive ammonia SCR system

    Science.gov (United States)

    Toner, Joel G.; Narayanaswamy, Kushal; Szekely, Jr., Gerald A.; Najt, Paul M.

    2016-12-06

    A method for controlling ammonia generation in an exhaust gas feedstream output from an internal combustion engine equipped with an exhaust aftertreatment system including a first aftertreatment device includes executing an ammonia generation cycle to generate ammonia on the first aftertreatment device. A desired air-fuel ratio output from the engine and entering the exhaust aftertreatment system conducive for generating ammonia on the first aftertreatment device is determined. Operation of a selected combination of a plurality of cylinders of the engine is selectively altered to achieve the desired air-fuel ratio entering the exhaust aftertreatment system.

  7. Synthesis Methods, Microscopy Characterization and Device Integration of Nanoscale Metal Oxide Semiconductors for Gas Sensing

    OpenAIRE

    Vander Wal, Randy L.; Berger, Gordon M.; Kulis, Michael J.; Hunter, Gary W; Laura Evans; Xu, Jennifer C.

    2009-01-01

    A comparison is made between SnO2, ZnO, and TiO2 single-crystal nanowires and SnO2 polycrystalline nanofibers for gas sensing. Both nanostructures possess a one-dimensional morphology. Different synthesis methods are used to produce these materials: thermal evaporation-condensation (TEC), controlled oxidation, and electrospinning. Advantages and limitations of each technique are listed. Practical issues associated with harvesting, purification, and integration of these materials into sensing ...

  8. Photoacoustic trace gas sensing : application to fruit and insects

    NARCIS (Netherlands)

    Persijn, Stefan Timotheüs

    2001-01-01

    A novel photoacoustic spectrometer has been applied to study trace gas emissions by fruit and insects. The spectrometer is based on a newly designed CO laser that can operate on 400 laser lines between 5.1-8.0 and 2.8-4.1 micrometer (delta v=1 and 2 mode, respectively). The spectrometer is equipped

  9. Specular reflection based sensing surface deformation of gas tungsten arc weld pool

    Institute of Scientific and Technical Information of China (English)

    Zhang Shiliang; Gao Jinqiang; Wu Chuansong; Zhang Yuming

    2007-01-01

    A sensing system is developed to measure the weld pool boundary and pool surface deformation in gas tungsten arc welding. LaserStrobe technique is used to eliminate the strong arc light interference, and specular reflection from the pool surface is sensed to describe the relation between the deformed stripes and pool surface depression. Clear images of both the pool boundary and the deformed stripes edges are obtained during gas tungsten arc welding process, which lays foundation for real-time monitoring the pool surface depression and weld penetration.

  10. Electrochemical sensing platform amplified with a nanobiocomposite of L-phenylalanine ammonia-lyase enzyme for the detection of capsaicin.

    Science.gov (United States)

    Sabela, Myalowenkosi I; Mpanza, Thabani; Kanchi, Suvardhan; Sharma, Deepali; Bisetty, Krishna

    2016-09-15

    The present study involves the development of a sensitive electrochemical biosensor for the determination of capsaicin extracted from chilli fruits, based on a novel signal amplification strategy using enzyme technology. For the first time, platinum electrode modified with multiwalled carbon nanotubes where phenylalanine ammonia-lyase enzyme was immobilized using nafion was characterized by attenuated total reflectance infrared spectroscopy, transmittance electron microscopy and thermo-gravimetric analysis supported by computational methods. Cyclic and differential pulse voltammetry measurements were performed to better understand the redox mechanism of capsaicin. The performance of the developed electrochemical biosensor was tested using spiked samples with recoveries ranging from 98.9 to 99.6%. The comparison of the results obtained from bare and modified platinum electrodes revealed the sensitivity of the developed biosensor, having a detection limit (S/N=3) of 0.1863µgmL(-1) and electron transfer rate constant (ks) of 3.02s(-1). Furthermore, adsorption and ligand-enzyme docking studies were carried out to better understand the redox mechanisms supported by density functional theory calculations. These results revealed that capsaicin forms hydrogen bonds with GLU355, GLU541, GLU586, ARG and other amino acids of the hydrophobic channel of the binding sites thereby facilitating the redox reaction for the detection of capsaicin.

  11. Fabrication of TiO2 Nanotube Thin Films and Their Gas Sensing Properties

    Directory of Open Access Journals (Sweden)

    Yongxiang Li

    2009-01-01

    Full Text Available The fabrication process and the growth mechanism of titanium/titania nanotubes prepared by anodization process is reviewed, and their applications in the fields of dye sensitized solar cells, photocatalysts, electrochromic devices, gas sensors, and biomaterials are presented. The anodization of Ti thin films on different substrates and the growth process of anodic titanium oxide are described using the current-time curves. Special attention is paid on the influences of the initial film smoothness on the resulted nanoporous morphologies. The “threshold barrier layer thickness model” is used to discuss the growth mechanism. As a case study for gas sensing, anodized highly ordered TiO2 nanotube arrays and nanoporous thin films that show porous surface with an average diameter of 25 nm and interpore distance of 40 nm were prepared. Gas sensors based on such nanotube arrays and nanoporous thin films were fabricated, and their sensing properties were investigated. Excellent H2 gas sensing properties were obtained for sensors prepared from these highly ordered TiO2 nanotube arrays, which present stable response even at a low operating temperature of 90°C. Based on our experimental results, “H-induced O2− desorption” mechanism was used for explaining the hydrogen gas sensing mechanism.

  12. Characteristics of several NIR tuneable diode lasers for spectroscopic based gas sensing: A comparison

    Science.gov (United States)

    Weldon, Vincent; McInerney, David; Phelan, Richard; Lynch, Michael; Donegan, John

    2006-04-01

    Tuneable laser diodes were characterized and compared for use as tuneable sources in gas absorption spectroscopy. Specifically, the characteristics of monolithic widely tuneable single frequency lasers, such as sampled grating distributed Bragg reflector laser and modulated grating Y-branch laser diodes, recently developed for optical communications, with operating wavelengths in the 1520 nm ≤ λ ≤ 1570 nm are compared. The assessment also includes an external cavity laser and a distributed feedback laser for water vapour detection, both emitting at 935 nm. Characteristics investigated include side-mode suppression ratio, ease of tuning, tuning range, spectral emission linewidth, frequency stability and wavelength modulation. While some characteristics differ significantly across the range of lasers, each device has a number of useful intrinsic qualities for gas sensing. Specifically, the modulated grating Y laser and the sampled grating DBR laser have wide quasi-continuous tuneability (30-40 nm) and display relatively low residual amplitude noise when grating-modulated in a harmonic detection scheme. They are particularly suitable for multi-gas sensing. ECLs are also capable of wide quasi-continuous tuneability (100 nm) but their architecture renders them unsuitable for gas sensing application outside a controlled laboratory environment. DFB devices are by far the easiest with which to work but their modest tuneability (4 nm maximum by temperature) almost invariably limits their use to single gas sensing applications.

  13. Metal-core@metal oxide-shell nanomaterials for gas-sensing applications: a review

    Science.gov (United States)

    Mirzaei, A.; Janghorban, K.; Hashemi, B.; Neri, G.

    2015-09-01

    With an ever-increasing number of applications in many advanced fields, gas sensors are becoming indispensable devices in our daily life. Among different types of gas sensors, conductometric metal oxide semiconductor (MOS) gas sensors are found to be the most appealing for advanced applications in the automotive, biomedical, environmental, and safety sectors because of the their high sensitivity, reduced size, and low cost. To improve their sensing characteristics, new metal oxide-based nanostructures have thus been proposed in recent years as sensing materials. In this review, we extensively review gas-sensing properties of core@ shell nanocomposites in which metals as the core and metal oxides as the shell structure, both of nanometer sizes, are assembled into a single metal@metal oxide core-shell. These nanostructures not only combine the properties of both noble metals and metal oxides, but also bring unique synergetic functions in comparison with single-component materials. Up-dated achievements in the synthesis and characterization of metal@metal oxide core-shell nanostructures as well as their use in MOS sensors are here reported with the main objective of providing an overview about their gas-sensing properties.

  14. Ammonia and greenhouse gas emissions from a modern U.S. swine breeding-gestation-farrowing system

    Science.gov (United States)

    Stinn, John P.; Xin, Hongwei; Shepherd, Timothy A.; Li, Hong; Burns, Robert T.

    2014-12-01

    Aerial emissions from livestock production continue to be an area of attention and concern for both the potential health and environmental impacts. However, information of gaseous, especially greenhouse gas (GHG), emissions for swine breeding/gestation and farrowing production systems is limited. The purpose of this study was to quantify ammonia (NH3), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) concentrations and emissions from a modern breeding-gestation-farrowing system located in central Iowa, USA. A 4300-sow farm was selected for the extensive field monitoring which employed a Mobile Air Emission Monitoring Unit equipped with state-of-the-art gas analyzers and a data acquisition system. The monitored portion of the farm facility consisted of a deep-pit breeding/early gestation (B/EG) barn (1800 head), a deep-pit late gestation (LG) barn (1800 head), and two shallow-pit (pull-plug) farrowing rooms (40 head per room). A dynamic flux chamber was used to monitor gaseous emissions from the external manure storage for the farrowing rooms. Data were collected for 29 consecutive months (January 2011 through June 2013). Daily indoor NH3, CO2, N2O, and CH4 concentrations (ppm, mean ± SD) were 12.0 (±7.6), 1594 (±797), 0.31 (±0.11), and 28.5 (±9.8), respectively, in the breeding/gestation barns; and 9.7 (±4.1), 1536 (±701), 0.30 (±0.10), and 78.3 (±37), respectively, in the farrowing rooms. Daily emissions per animal unit (AU, 500 kg live weight) were 35.1 g NH3, 7.46 kg CO2, 0.17 g N2O, and 263.4 g CH4 for sows in the B/EG barn; and 28.2 g NH3, 6.50 kg CO2, 0.12 g N2O, and 201.3 g CH4 for sows in the LG barn. The average daily emissions per AU (sow and piglets) of the farrowing rooms during the lactation period (birth to weaning) were: 59.7 g NH3, 16.4 kg CO2, 0.73 g N2O, and 107 g CH4. For the monitored period, the external manure storage had the following average daily emission per m2 surface area: 1.26 g NH3, 137 g CO2, and 94.8 g CH4, which

  15. Temperature Sensing for Oil, Gas, and Structural Analysis

    Science.gov (United States)

    2006-01-01

    In 1996, Systems and Processes Engineering Corporation (SPEC), of Austin, Texas, undertook a NASA Small Business Innovation Research (SBIR) contract with Langley Research Center to develop a compact and lightweight digital thermal sensing (DTS) system for monitoring the cryogenic tanks on the X-33 prototype aircraft. That technology, along with a processor developed by SPEC for Goddard Space Flight Center, was space-qualified and integrated into several NASA missions. SPEC formed an ancillary organization, SensorTran, Inc., to continue work developing the DTS technology for a variety of commercial and industrial applications.

  16. Controlled Synthesis of Hierarchically Assembled Porous ZnO Microspheres with Enhanced Gas-Sensing Properties

    Directory of Open Access Journals (Sweden)

    Shengsheng You

    2015-01-01

    Full Text Available The ZnO microspheres constructed by porous nanosheets were successfully synthesized by calcinating zinc hydroxide carbonate (ZHC microspheres obtained by a sample hydrothermal method. The samples were characterized in detail with scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray diffraction (XRD, and thermogravimetric and differential scanning calorimetry (TG-DSC. The results indicated that the prepared ZnO microspheres were well crystalline with wurtzite hexagonal phase. The effects of reaction time, temperature, the amount of trisodium citrate, and urea on the morphology of ZnO microspheres were studied. The formation mechanism of porous ZnO microspheres was discussed. Furthermore, the gas-sensing properties for detection of organic gas of the prepared porous ZnO microspheres were investigated. The results indicated that the prepared porous ZnO microspheres exhibited high gas-sensing properties for detection of ethanol gas.

  17. Flue-Gas Desulfurization Gypsum Effects on Urea-Degrading Bacteria and Ammonia Volatilization From Broiler Litter

    Science.gov (United States)

    A major concern of the broiler industry is the volatilization of ammonia (NH3) from the mixture of bedding material and broiler excretion that covers the floor of broiler houses. Gypsum has been proposed as a litter amendment to reduce NH3 volatilization, but reports of NH3 abatement vary among stu...

  18. Manure-DNDC: a biogeochemical process model for quantifying greenhouse gas and ammonia emissions from livestock manure systems

    Science.gov (United States)

    From the point of view of biogeochemistry, manure is a complex of organic matter containing minor minerals. When manure is excreted by animals, it undergoes a series of reactions such as decomposition, hydrolysis, ammonia volatilization, nitrification, denitrification, and fermentation from which ca...

  19. Large-area nanopatterned graphene for ultrasensitive gas sensing

    DEFF Research Database (Denmark)

    Cagliani, Alberto; Mackenzie, David Micheal Angus; Tschammer, Lisa Katharina

    2014-01-01

    Chemical vapor deposited (CVD) graphene is nanopatterned using a spherical block copolymer etch mask. The use of spherical rather than cylindrical block copolymers allows homogeneous patterning of cm-scale areas without any substrate surface treatment. Raman spectroscopy was used to study...... the controlled generation of point defects in the graphene lattice with increasing etching time, confirming that alongside the nanomesh patterning, the nanopatterned CVD graphene presents a high defect density between the mesh holes. The nanopatterned samples showed sensitivities for NO2 of more than one order...... of magnitude higher than for non-patterned graphene. NO2 concentrations as low as 300 ppt were detected with an ultimate detection limit of tens of ppt. This is the smallest value reported so far for non-UV illuminated graphene chemiresistive NO2 gas sensors. The dramatic improvement in the gas sensitivity...

  20. Superior Gas Sensing Properties of Monolayer PtSe2

    KAUST Repository

    Sajjad, Muhammad

    2016-12-15

    First-principles calculations of the structural and electronic properties of monolayer 1T-PtSe2 with adsorbed (a) NO2, (b) NO, (c) NH3, (d) H2O, (e) CO2, and (f) CO molecules are discussed. The results point to great potential of the material in gas sensor applications. Superior sensitivity is demonstrated by transport calculations using the nonequilibrium Green\\'s function method.

  1. Degradation of Aflatoxins B1 Which in Peanut by Ammonia Gas Method%氨气熏蒸法降解花生中的黄曲霉素B1

    Institute of Scientific and Technical Information of China (English)

    赵国斌

    2014-01-01

    Peanuts which contaminated by aflatoxin was treated by ammonia gas method and AFB1 was degraded. Effect of concentration of ammonia gas, temperature, moisture of peanuts and time of degradation rate of AFB1 was investigated by single factor experiments , and the optimal condition was determined. The results show that the optimum conditions for ammonia gas method were concentration of ammonia gas 10 %, temperature 40 ℃, moisture of peanuts 30%, ammonia smoked time 96 h, the highest degradation rate 95.06%, the degradation effect was remarkable. Ammonia gas method is easy to operate, low cost, high degradation rate, and the ammonia's source is rich, it is suitable for large-scale practical application.%采用氨气熏蒸法对污染黄曲霉毒素AFB1的花生进行处理,使其中的AFB1得到降解,并通过单因素实验考察氨气浓度、氨熏温度、花生含水量和蒸熏时间等条件对降解率的影响,得到最优条件。结果表明,氨气熏蒸法最佳条件为:氨气浓度10%,熏蒸温度40℃,花生含水量30%,氨熏时间96 h,最高降解率为95.06%,降解效果显著。氨气熏蒸法易于操作、成本低廉、降解率高,且氨气来源广泛,适合大规模实际应用。

  2. Selective Sensing of Gas Mixture via a Temperature Modulation Approach: New Strategy for Potentiometric Gas Sensor Obtaining Satisfactory Discriminating Features

    Science.gov (United States)

    Li, Fu-an; Jin, Han; Wang, Jinxia; Zou, Jie; Jian, Jiawen

    2017-01-01

    A new strategy to discriminate four types of hazardous gases is proposed in this research. Through modulating the operating temperature and the processing response signal with a pattern recognition algorithm, a gas sensor consisting of a single sensing electrode, i.e., ZnO/In2O3 composite, is designed to differentiate NO2, NH3, C3H6, CO within the level of 50–400 ppm. Results indicate that with adding 15 wt.% ZnO to In2O3, the sensor fabricated at 900 °C shows optimal sensing characteristics in detecting all the studied gases. Moreover, with the aid of the principle component analysis (PCA) algorithm, the sensor operating in the temperature modulation mode demonstrates acceptable discrimination features. The satisfactory discrimination features disclose the future that it is possible to differentiate gas mixture efficiently through operating a single electrode sensor at temperature modulation mode. PMID:28287492

  3. Gas sensing behaviour of cerium oxide and magnesium aluminate composites

    Indian Academy of Sciences (India)

    N NITHYAVATHY; V RAJENDRAN; L JOHN BERCHMANS; M MAAZA; S KRITHIKA; S ARUNMETHA

    2017-08-01

    Composites of cerium oxide (CeO$_2$) and magnesium aluminate (MgAl$_2$O$_4$) were prepared by the moltensalt synthesis (MSS) method at 1130 K. The composite samples were named as MA, MAC0.07 and MAC0.14 (at CeO$_2$:0, 0.07 and 0.14 g in MgAl$_2$O$_4$, respectively) and these were characterized by X-ray diffraction and energy-dispersiveX-ray analyses. It is seen that the microstructure of the composite samples are quite similar except for a small increasein particle size. The energy-dispersive X-ray analyses provide the presence of concentration of Ce, Mg, Al and O in thecomposite. Scanning electron microscope, coupled with energy-dispersive X-ray analysis (SEM-EDAX) was used to identifythe morphology, microstructure and elemental composition of the prepared samples. The decomposition and dissociationreactions of the precursors were determined using differential thermal and thermogravimetric analysis (TGA). A lone pairof the electron state was identified from the electro paramagnetic resonance spectrum. An optical energy band gap of 3.3 eV was calculated from the UV–Vis absorbance spectra. The gas response to changes in oxygen (O$_2$), carbon monoxide (CO) (at 0.5, 1.0 and 1.5 bar) and ethanol (at 50 and 100 ppm) was quantitatively analysed in all the samples at differentoperating temperatures (300-500 K). The magnitude of the temperature varied linearly regardless of the gas pressure insidethe chamber, by increasing the supply in the heating pad, mounted below the sensor sample. The composite samples indicatea good response to different gases with detection of the smallest change in gas pressure.

  4. Gas-aerosol partitioning of ammonia in biomass burning plumes: Implications for the interpretation of spaceborne observations of ammonia and the radiative forcing of ammonium nitrate

    Science.gov (United States)

    Paulot, F.; Paynter, D.; Ginoux, P.; Naik, V.; Whitburn, S.; Van Damme, M.; Clarisse, L.; Coheur, P.-F.; Horowitz, L. W.

    2017-08-01

    Satellite-derived enhancement ratios of NH3 relative to CO column burden (ERNH3/CO) in fires over Alaska, the Amazon, and South Equatorial Africa are 35, 45, and 70% lower than the corresponding ratio of their emissions factors (EFNH3/CO) from biomass burning derived from in situ observations. Simulations performed using the Geophysical Fluid Dynamics Laboratory AM3 global chemistry-climate model show that these regional differences may not entirely stem from an overestimate of NH3 emissions but rather from changes in the gas-aerosol partitioning of NH3 to NH4+. Differences between ERNH3/CO and EFNH3/CO are largest in regions where EFNOx/NH3 is high, consistent with the production of NH4NO3. Biomass burning is estimated to contribute 11-23% of the global burden and direct radiative effect (DRE) of NH4NO3 (-15 to -28 mW m-2), despite accounting for less than 6% of the global source of NH3. Production of NH4NO3 is largely concentrated over the Amazon and South Equatorial Africa, where its DRE can reach -1.9 W m-2 during the biomass burning season.

  5. Photoluminescence and hydrogen gas-sensing properties of titanium dioxide nanostructures synthesized by hydrothermal treatments

    CSIR Research Space (South Africa)

    Sikhwivhilu, LM

    2012-03-01

    Full Text Available -1 ACS Appl. Mater. Interfaces 2012, 4, 1656-1665 dx.doi.org/10.1021/am2018089 Photoluminescence and Hydrogen Gas-Sensing Properties of Titanium Dioxide Nanostructures Synthesized by Hydrothermal Treatments Lucky M. Sikhwivhilu, Siyasanga Mpelane...

  6. Airborne Shortwave Infrared Spectral Remote Sensing as a Direct Prospecting Method for Oil and Gas Resources

    Institute of Scientific and Technical Information of China (English)

    杨柏林

    1994-01-01

    The spectral characters of hydrocarbons in some oil-bearing strata and soil layers ouer oil and gas reservoirs in the Junggar Basin and northern Tarim Basin in Xinjng are compared with those of chemically pure hydrocarbons.The hydrocarbons are characterized by the bi-absorption at 2310nm and 2350nm.Hydrocarbon and radioactive anomalies in oil and gas terrains are found much more widespread than carbonate alterations.Based on the spectra of heavy hydrocarbons related to oil between 2270nm and 2460nm and refined data treatme nt, remote sensing may hold encouraging promise as a directly prospecting technique for oil and gas resources.

  7. Development of ammonia sensors by using conductive polymer/hydroxyapatite composite materials.

    Science.gov (United States)

    Huixia, Li; Yong, Liu; Lanlan, Luo; Yanni, Tan; Qing, Zhang; Kun, Li

    2016-02-01

    In order to improve the gas sensing properties, hydroxyapatite (HAp)-based composites were prepared by mixing with different contents of conductive polymers: polypyrrole (PPy) and polyaniline (PAni). The compositions, microstructures and phase constitutions of polymer/HAp composites were characterized, and the sensing properties were studied using a chemical gas sensing (CGS-8) system. The results showed that, compared to pure HAp, the sensitivities of the composites to ammonia were improved significantly. 5%PPy/HAp and 20%PAni/HAp composites exhibited the best sensitivities to ammonia, and the sensitivities at 500ppm were 86.72% and 86.18%, respectively. Besides, the sensitivity of 5%PPy/HAp at 1000ppm was up to 90.7%. Compared to pure PPy and PAni, the response and the recovery time of 5%PPy/HAp and 20%PAni/HAp at 200ppm were shortened several times, and they were 24s/245s and 15s/54s, respectively. In addition, the composites showed a very high selectivity to ammonia. The mechanism for the enhancement of the sensitivity to ammonia was also discussed. The polymer/HAp composites are very promising in applications of ammonia sensors.

  8. Design of waveguide-integrated graphene devices for photonic gas sensing

    Science.gov (United States)

    Cheng, Zhenzhou; Goda, Keisuke

    2016-12-01

    We present waveguide-integrated graphene devices for photonic gas sensing. In a gas environment, graphene’s conductivity is changed by adsorbed gas molecules which serve as charge-carrier donors or acceptors. To accurately probe gas-induced variations in the graphene’s conductivity, we optimize the graphene’s Fermi level and spectral region. Then, we propose graphene-on-silicon and graphene-on-germanium suspended membrane slot waveguides in which propagating light in the waveguide has a strong interaction with the top graphene layer. The gas concentration can be calculated by measuring the spectrum of the optical reflection from the waveguide Bragg grating. The maximum sensitivity of the waveguide-integrated gas sensor can reach one part per million for sensing gaseous nitrogen dioxide. Its sensitivity is about 20 times higher than that of the graphene-covered microfiber sensor and is comparable with that of a graphene plasmonic sensor. The fabrication of the proposed graphene device is CMOS compatible. Our results pave a way for chip-integrated sensitive photonic gas sensors.

  9. Investigating gas sensing mechanism of graphene oxide (GO) thin films through cross-selectivity to various gases

    Science.gov (United States)

    Kumar, Shani; Dhingra, Vishal; Garg, Amit; Chowdhuri, Arijit

    2016-05-01

    Worldwide researchers are actively engaged in utilizing Graphene and its related materials in gas sensing applications. A high surface-to-volume ratio that offers scope of optimization leading to enhanced sensing performance besides lower sensor operating temperatures are some advantages that graphene based sensors possess over conventional semiconducting metal oxide (SMO) sensors. Conventional SMO based gas sensors are known to suffer from problems of cross-selectivity where selectivity is understood to be a gas sensor's ability to preferentially detect one particular gas without responding to or experiencing interference from other gases present in the ambient. In the current study gas sensing mechanism of Graphene oxide (GO) thin films is investigated by repeatedly exposing the sensing configuration to various gases and its cross-selectivity response to the same is examined. In the investigation typical gas sensing response characteristics of the sensor configuration are studied in both oxidizing as well as reducing environments. The gas sensing data is acquired by means of Keithley 6487 picoammeter which is interfaced with a customized Gas Sensing Test Rig (GSTR) that provides a controlled ambient to the sensors for measurement of reproducible characteristics. GSTR further provided the option of varying the operating temperature and gas concentration for the different sensor configurations under study. XRD studies indicate formation of GO with typical crystallite size of 4.2 nm. UV-Vis investigations reveal a typical band-gap of 4.42 (eV) which is in conformity with those reported in the available literature.1,2

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

    Science.gov (United States)

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

    2014-06-01

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

  11. Gas/liquid sensing via chemotaxis of Euglena cells confined in an isolated micro-aquarium.

    Science.gov (United States)

    Ozasa, Kazunari; Lee, Jeesoo; Song, Simon; Hara, Masahiko; Maeda, Mizuo

    2013-10-21

    We demonstrate on-chip gas/liquid sensing by using the chemotaxis of live bacteria (Euglena gracilis) confined in an isolated micro-aquarium, and gas/liquid permeation through porous polydimethylsiloxane (PDMS). The sensing chip consisted of one closed micro-aquarium and two separated bypass microchannels along the perimeter of the micro-aquarium. Test gas/liquid and reference samples were introduced into the two individual microchannels separately, and the gas/liquid permeated through the PDMS walls and dissolved in the micro-aquarium water, resulting in a chemical concentration gradient in the micro-aquarium. By employing the closed micro-aquarium isolated from sample flows, we succeeded in measuring the chemotaxis of Euglena for a gas substance quantitatively, which cannot be achieved with the conventional flow-type or hydro-gel-type microfluidic devices. We found positive (negative) chemotaxis for CO2 concentrations below (above) 15%, with 64 ppm as the minimum concentration affecting the cells. We also observed chemotaxis for ethanol and H2O2. By supplying culture medium via the microchannels, the Euglena culture remained alive for more than 2 months. The sensing chip is thus useful for culturing cells and using them for environmental toxicity/nutrition studies by monitoring their motion.

  12. Hydrogen Gas Sensing Characteristics of Nanostructured NiO Thin Films Synthesized by SILAR Method

    Science.gov (United States)

    Karaduman, Irmak; Çorlu, Tugba; Yıldırım, M. Ali; Ateş, Aytunç; Acar, Selim

    2017-03-01

    Nanostructured NiO thin films have been synthesized by a facile, low-cost successive ionic layer adsorption and reaction (SILAR) method, and the effects of the film thickness on their hydrogen gas sensing properties investigated. The samples were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) analysis, and energy-dispersive x-ray analysis. The XRD results revealed that the crystallinity improved with increasing thickness, exhibiting polycrystalline structure. SEM studies showed that all the films covered the glass substrate well. According to optical absorption measurements, the optical bandgap decreased with increasing film thickness. The gas sensing properties of the nanostructured NiO thin films were studied as a function of operating temperature and gas concentration. The samples showed good sensing performance of H2 gas with high response. The maximum response was 75% at operating temperature of 200°C for hydrogen gas concentration of 40 ppm. These results demonstrate that nanostructured NiO thin films synthesized by the SILAR method have potential for application in hydrogen detection.

  13. Plasmonic nanopatch array with integrated metal-organic framework for enhanced infrared absorption gas sensing

    Science.gov (United States)

    Chong, Xinyuan; Kim, Ki-joong; Zhang, Yujing; Li, Erwen; Ohodnicki, Paul R.; Chang, Chih-Hung; Wang, Alan X.

    2017-06-01

    In this letter, we present a nanophotonic device consisting of plasmonic nanopatch array (NPA) with integrated metal-organic framework (MOF) for enhanced infrared absorption gas sensing. By designing a gold NPA on a sapphire substrate, we are able to achieve enhanced optical field that spatially overlaps with the MOF layer, which can adsorb carbon dioxide (CO2) with high capacity. Experimental results show that this hybrid plasmonic-MOF device can effectively increase the infrared absorption path of on-chip gas sensors by more than 1100-fold. The demonstration of infrared absorption spectroscopy of CO2 using the hybrid plasmonic-MOF device proves a promising strategy for future on-chip gas sensing with ultra-compact size.

  14. The gas sensing properties of TiO2 nanotubes synthesized by hydrothermal method

    Institute of Scientific and Technical Information of China (English)

    Yan Li Wang; Shun Tan; Jia Wang; Zhi Jin Tan; Qiu Xia Wu; Zheng Jiao; Ming Hong Wu

    2011-01-01

    In this paper, the TiO2 nanotubes were synthesized by hydrothermal method usinga 10 mol/LNaOH aqueous solution at 150 ℃. The structure of prepared materials was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET). The prepared TiO2 nanotubes were used to prepare thick film gas sensors and the gas sensing properties to various gases were tested. Results show the prepared TiO2 nanotube gas sensors responses to ethanol under dry condition at 450 ℃. This could be attributed to the fact that it had high porous morphology and a higher pore volume, which can promote the diffusion of ethanol deep inside the films and improve the sensor response. Moreover, the gas sensor made with nanotubes exhibit high selective response towards ethanol gas compared with H2, CO, acetone.

  15. Suggestion of transform synthesis ammonia co-production natural gas remission imbalance between supply and demand%改造合成氨联产天然气缓解供需矛盾的建议

    Institute of Scientific and Technical Information of China (English)

    李志坚; 温倩

    2014-01-01

    通过对我国合成氨和天然气产业现状的分析,提出了合成氨联产天然气的初步改造方案,并进行了经济分析,预测了改造效果和提出了政策建议。%The paper analyzes industry status quo of synthesis ammonia and natural gas in China, proposes preliminary modification scheme of synthesis ammonia co-production natural gas, it also processes economic analysis and forecasts reforestation effect, at last, it proposes policy suggestion.

  16. Micro flame-based detector suite for universal gas sensing.

    Energy Technology Data Exchange (ETDEWEB)

    Hamilton, Thomas Warren; Washburn, Cody M.; Moorman, Matthew Wallace; Manley, Robert George; Lewis, Patrick Raymond; Miller, James Edward; Clem, Paul Gilbert; Shelmidine, Gregory J.; Manginell, Ronald Paul; Okandan, Murat

    2005-11-01

    A microflame-based detector suit has been developed for sensing of a broad range of chemical analytes. This detector combines calorimetry, flame ionization detection (FID), nitrogen-phosphorous detection (NPD) and flame photometric detection (FPD) modes into one convenient platform based on a microcombustor. The microcombustor consists in a micromachined microhotplate with a catalyst or low-work function material added to its surface. For the NPD mode a low work function material selectively ionizes chemical analytes; for all other modes a supported catalyst such as platinum/alumina is used. The microcombustor design permits rapid, efficient heating of the deposited film at low power. To perform calorimetric detection of analytes, the change in power required to maintain the resistive microhotplate heater at a constant temperature is measured. For FID and NPD modes, electrodes are placed around the microcombustor flame zone and an electrometer circuit measures the production of ions. For FPD, the flame zone is optically interrogated to search for light emission indicative of deexcitation of flame-produced analyte compounds. The calorimetric and FID modes respond generally to all hydrocarbons, while sulfur compounds only alarm in the calorimetric mode, providing speciation. The NPD mode provides 10,000:1 selectivity of nitrogen and phosphorous compounds over hydrocarbons. The FPD can distinguish between sulfur and phosphorous compounds. Importantly all detection modes can be established on one convenient microcombustor platform, in fact the calorimetric, FID and FPD modes can be achieved simultaneously on only one microcombustor. Therefore, it is possible to make a very universal chemical detector array with as little as two microcombustor elements. A demonstration of the performance of the microcombustor in each of the detection modes is provided herein.

  17. Temperature and acidity effects on WO{sub 3} nanostructures and gas-sensing properties of WO{sub 3} nanoplates

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Huili [School of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin University of Technology, Tianjin 300384 (China); Liu, Zhifang; Yang, Jiaqin; Guo, Wei [Department of Materials Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (MOE), TKL of Metal and Molecule-based Material Chemistry, Synergetic Innovation Centre of Chemical Science and Engineering (Tianjin), College of Chemistry, Nankai University, Tianjin 300071 (China); Zhu, Lianjie, E-mail: zhulj@tjut.edu.cn [School of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin University of Technology, Tianjin 300384 (China); Zheng, Wenjun, E-mail: zhwj@nankai.edu.cn [Department of Materials Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (MOE), TKL of Metal and Molecule-based Material Chemistry, Synergetic Innovation Centre of Chemical Science and Engineering (Tianjin), College of Chemistry, Nankai University, Tianjin 300071 (China)

    2014-09-15

    Graphical abstract: Generally, large acid quantity and high temperature are beneficial to the formation of anhydrous WO3, but the acidity effect on the crystal phase is weaker than that of temperature. Large acid quantity is found helpful to the oriented growth of tungsten oxides, forming a nanoplate-like product. - Highlights: • Large acid quantity is propitious to the oriented growth of a WO{sub 3} nanoplate. • Effect of acid quantity on crystal phases of products is weaker than that of temperature. • One step hydrothermal synthesis of WO{sub 3} is facile and can be easily scaled up. • A WO{sub 3} nanoplate shows a fast response and distinct sensing selectivity to acetone gas. - Abstract: WO{sub 3} nanostructures were successfully synthesized by a facile hydrothermal method using Na{sub 2}WO{sub 4}·2H{sub 2}O and HNO{sub 3} as raw materials. They are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The specific surface area was obtained from N{sub 2} adsorption–desorption isotherm. The effects of the amount of HNO{sub 3}, hydrothermal temperature and reaction time on the crystal phases and morphologies of the WO{sub 3} nanostructures were investigated in detail, and the reaction mechanism was discussed. Large amount of acid is found for the first time to be helpful to the oriented growth of tungsten oxides, forming nanoplate-like products, while hydrothermal temperature has more influence on the crystal phase of the product. Gas-sensing properties of the series of as-prepared WO{sub 3} nanoplates were tested by means of acetone, ethanol, formaldehyde and ammonia. One of the WO{sub 3} nanoplates with high specific surface area and high crystallinity displays high sensitivity, fast response and distinct sensing selectivity to acetone gas.

  18. Surface plasmon sensing of gas phase contaminants using optical fiber.

    Energy Technology Data Exchange (ETDEWEB)

    Thornberg, Steven Michael; White, Michael I.; Rumpf, Arthur Norman; Pfeifer, Kent Bryant

    2009-10-01

    Fiber-optic gas phase surface plasmon resonance (SPR) detection of several contaminant gases of interest to state-of-health monitoring in high-consequence sealed systems has been demonstrated. These contaminant gases include H{sub 2}, H{sub 2}S, and moisture using a single-ended optical fiber mode. Data demonstrate that results can be obtained and sensitivity is adequate in a dosimetric mode that allows periodic monitoring of system atmospheres. Modeling studies were performed to direct the design of the sensor probe for optimized dimensions and to allow simultaneous monitoring of several constituents with a single sensor fiber. Testing of the system demonstrates the ability to detect 70mTorr partial pressures of H{sub 2} using this technique and <280 {micro}Torr partial pressures of H{sub 2}S. In addition, a multiple sensor fiber has been demonstrated that allows a single fiber to measure H{sub 2}, H{sub 2}S, and H{sub 2}O without changing the fiber or the analytical system.

  19. Simulation analysis of effect of inert gas on ammonia synthesis loop%惰性气体对氨合成回路影响的模拟分析

    Institute of Scientific and Technical Information of China (English)

    袁皞; 黄梅

    2011-01-01

    为了让氨合成生产装置能在高产、优质、低消耗的工况下运行.应用PRO/Ⅱ模拟软件,选择SRK热力学方程对高压下的氨合成回路进行模拟计算,并通过改变驰放气中惰性气体摩尔分数分析对氨合成回路的影响.得出循环气中的惰性气体摩尔分数与氨净值、循环机功耗、原料气消耗量以及氨合成塔出口温度间的变化关系,从中找出合理的惰性气体摩尔分数,用以指导氨合成的现场生产.%In order to achieve high yield, better quality of ammonia product, low consumption in ammonia plant,the ammonia synthesis loop at high pressure was simulated by employing process simulation software PRO/Ⅱ and SRK thermodynamic equation. The effect of inert gas on ammonia synthesis loop was analyzed by changing the mole fraction of inert gas in relief. The relationship among between the mole fraction of inert gas and ammonia mole fraction, the shaft power of recycle compressor, fresh gas consumption, and the temperature of converter outlet stream was analyzed, from which the optimal mole fraction of inert gas was determined to direct the ammonia plant to achieve the best performance.

  20. Hexanal Gas Detection Using Chitosan Biopolymer as Sensing Material at Room Temperature

    Directory of Open Access Journals (Sweden)

    Devi Shantini

    2016-01-01

    Full Text Available Hexanal was identified as one of the major volatile gases which are produced in degraded dairy products and wood industries. Therefore, preliminary study on hexanal gas detection with the laboratory scale was carried out in this paper. Electrical testing with chitosan as a sensing material to sense hexanal gas in low concentration was carried out at room temperature. Chitosan sensor was fabricated by using electrochemical deposition technique to form active sensing layer. The response of the chitosan film sensor (CFS towards hexanal was tested via electrical testing by exposing different hexanal concentrations ranging between 20 ppm, 100 ppm, 200 ppm, and 300 ppm using air as a carrier gas. Sensing properties of the CFS toward hexanal exposure including responsibility, recovery, repeatability, stability, and selectively were studied. Overall, our result suggested that hexanal sensor based on chitosan was able to perform well at room temperature demonstrated by good response, good recovery, good repeatability, good stability, and good selectively. This simple and low cost sensor has high potential to be utilized in early quality degradation detection in dairy products and can be used to monitor the level of hexanal exposure in wood industries.

  1. Enhancement of photoresponse and UV-assisted gas sensing with Au decorated ZnO nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Li Yinhua [School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0620 (United States); State Key Laboratory of Fine Chemicals, R and D Center of Membrane Science and Technology, School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China); Gong Jian [School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0620 (United States); He Gaohong [State Key Laboratory of Fine Chemicals, R and D Center of Membrane Science and Technology, School of Chemical Engineering, Dalian University of Technology, Dalian 116024 (China); Deng Yulin, E-mail: yulin.deng@chbe.gatech.edu [School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0620 (United States)

    2012-06-15

    To increase the photoresponsive and gas sensing properties of ZnO nanofibers under UV illumination, Au nanoparticles were introduced to the ZnO nanofibers (Au/ZnO) using electrospinning technique. It is found that adding Au nanoparticles into the ZnO nanofibers enhances significantly the photoresponse and makes the nanofibers also respond to visible light. The gas sensing performance with the assist of UV irradiation at room temperature was also improved greatly, e.g., the sensor response (SR) for 5 ppm ethanol increases from 0.12 to 0.31 by introducing 0.20 mol% of Au in ZnO nanofibers. The improvement of gas sensing performance is attributed to the enhanced photocatalytic reactions of organic gases on the Au/ZnO nanofibers surface. In addition, the sensitive behaviors of the nanofibers to ethanol, benzene, toluene and acetone under UV irradiation with different wavelengths were investigated and compared as well. Highlights: Black-Right-Pointing-Pointer Au/ZnO nanofiber sensors were successfully prepared using electrospinning. Black-Right-Pointing-Pointer The Au/ZnO sensors respond not only to UV light but also to visible light. Black-Right-Pointing-Pointer The response to organic analyte at room temperature is also greatly improved. Black-Right-Pointing-Pointer Schottky junction between Au and ZnO is one key for the improvement of sensing.

  2. Analytical Calculation of Sensing Parameters on Carbon Nanotube Based Gas Sensors

    Directory of Open Access Journals (Sweden)

    Elnaz Akbari

    2014-03-01

    Full Text Available Carbon Nanotubes (CNTs are generally nano-scale tubes comprising a network of carbon atoms in a cylindrical setting that compared with silicon counterparts present outstanding characteristics such as high mechanical strength, high sensing capability and large surface-to-volume ratio. These characteristics, in addition to the fact that CNTs experience changes in their electrical conductance when exposed to different gases, make them appropriate candidates for use in sensing/measuring applications such as gas detection devices. In this research, a model for a Field Effect Transistor (FET-based structure has been developed as a platform for a gas detection sensor in which the CNT conductance change resulting from the chemical reaction between NH3 and CNT has been employed to model the sensing mechanism with proposed sensing parameters. The research implements the same FET-based structure as in the work of Peng et al. on nanotube-based NH3 gas detection. With respect to this conductance change, the I–V characteristic of the CNT is investigated. Finally, a comparative study shows satisfactory agreement between the proposed model and the experimental data from the mentioned research.

  3. FBG sensing temperature characteristic and application in oil/gas down-hole measurement

    Institute of Scientific and Technical Information of China (English)

    Shaomin LI; Xiaoying LIU; You LI; Shenlong YANG; Chong LIU

    2009-01-01

    Fiber Bragg gratings (FBGs) have been used to sense numerous parameters such as strain, temperature, and pressure. Cost-effective multipoint measurements have been achieved by connecting FBGs in parallel, serial, and other topologies as well as by using spatial, wavelength, and time-domain multiplexing techniques. This paper presents a method of measuring temperature of the oil/gas down-hole. Detailed contents include the basic theory and characteristics of fiber gratings, analysis of the sensing mechanism of fiber-optic gratings, and the cross-sensitivity effect between temperature and strain; the method of making the light-source of the fiber-optic gratings and the technology of measuring wavelength shift, building an experimental system of the temperature measurement, and dealing with the experimental data. The paper makes a comparison of several kinds of FBG sensing systems used in oil/gas down-hole to measure temperature and the analysis of the experimental results of building the temperature measurement experimental sys-tem. It demonstrates that the fiber-optic grating sensing method is the best choice in all methods of measuring temperature in oil/gas down-hole, which has a brilliant applied prospect.

  4. Au sensitized ZnO nanorods for enhanced liquefied petroleum gas sensing properties

    Energy Technology Data Exchange (ETDEWEB)

    Nakate, U.T., E-mail: umesh.nakate@gmail.com [Department of Applied Physics, Defence Institute of Advanced Technology, Deemed University, Pune 411025 (India); Bulakhe, R.N.; Lokhande, C.D. [Department of Physics, Thin films Physics Laboratory, Shivaji University Kolhapur 416004 (India); Kale, S.N. [Department of Applied Physics, Defence Institute of Advanced Technology, Deemed University, Pune 411025 (India)

    2016-05-15

    Highlights: • We studied ZnO nanorods film for liquefied petroleum gas (LPG) sensing. • The Au sensitization on ZnO nanorods gives improved LPG sensing response. • The Au–ZnO shows 48% LPG response for 1040 ppm with fast response time of 50 S. • We proposed schematic for sensing mechanism using band diagram. - Abstract: The zinc oxide (ZnO) nanorods have grown on glass substrate by spray pyrolysis deposition (SPD) method using zinc acetate solution. The phase formation, surface morphology and elemental composition of ZnO films have been investigated using X-ray diffraction, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and energy dispersive X-ray (EDX) techniques. The liquefied petroleum gas (LPG) sensing response was remarkably improved by sensitization of gold (Au) surface noble metal on ZnO nanorods film. Maximum LPG response of 21% was observed for 1040 ppm of LPG, for pure ZnO nanorods sample. After Au sensitization on ZnO nanorods film sample, the LPG response greatly improved up to 48% at operating temperature 623 K. The improved LPG response is attributed Au sensitization with spill-over mechanism. Proposed model for LPG sensing mechanism discussed.

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

    Directory of Open Access Journals (Sweden)

    Adisorn Tuantranont

    2010-08-01

    Full Text Available 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.

  6. Multi-walled carbon nanotube-doped tungsten oxide thin films for hydrogen gas sensing.

    Science.gov (United States)

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

    2010-01-01

    In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO(3)) 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 WO(3) 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 WO(3) hydrogen sensor prepared by the E-beam method.

  7. Synergistic improvement of gas sensing performance by micro-gravimetrically extracted kinetic/thermodynamic parameters.

    Science.gov (United States)

    Guo, Shuanbao; Xu, Pengcheng; Yu, Haitao; Cheng, Zhenxing; Li, Xinxin

    2015-03-10

    A novel method is explored for comprehensive design/optimization of organophosphorus sensing material, which is loaded on mass-type microcantilever sensor. Conventionally, by directly observing the gas sensing response, it is difficult to build quantitative relationship with the intrinsic structure of the material. To break through this difficulty, resonant cantilever is employed as gravimetric tool to implement molecule adsorption experiment. Based on the sensing data, key kinetic/thermodynamic parameters of the material to the molecule, including adsorption heat -ΔH°, adsorption/desorption rate constants Ka and Kd, active-site number per unit mass N' and surface coverage θ, can be quantitatively extracted according to physical-chemistry theories. With gaseous DMMP (simulant of organophosphorus agents) as sensing target, the optimization route for three sensing materials is successfully demonstrated. Firstly, a hyper-branched polymer is evaluated. Though suffering low sensitivity due to insufficient N', the bis(4-hydroxyphenyl)-hexafluoropropane (BHPF) sensing-group exhibits satisfactory reproducibility due to appropriate -ΔH°. To achieve more sensing-sites, KIT-5 mesoporous-silica with higher surface-area is assessed, resulting in good sensitivity but too high -ΔH° that brings poor repeatability. After comprehensive consideration, the confirmed BHPF sensing-group is grafted on the KIT-5 carrier to form an optimized DMMP sensing nanomaterial. Experimental results indicate that, featuring appropriate kinetic/thermodynamic parameters of -ΔH°, Ka, Kd, N' and θ, the BHPF-functionalized KIT-5 mesoporous silica exhibits synergistic improvement among reproducibility, sensitivity and response/recovery speed. The optimized material shows complete signal recovery, 55% sensitivity improvement than the hyper-branched polymer and 2∼3 folds faster response/recovery speed than the KIT-5 mesoporous silica.

  8. Modification of hybrid NaY/ZSM-5/IDC zeolite composite with exchanged Cu2+ and its application as ammonia gas sensor

    Science.gov (United States)

    Lisnawati, Elsita; Krisnandi, Yuni Krisyuningsih; Triyono, Djoko

    2017-03-01

    A Modified NaY/ZSM-5/IDC zeolite composite with Cu2+ has been succsessfully prepared on the surface of quartz based Interdigitated Capacitor (IDC). The ZSM-5 was synthesized with double template using hydrothermal method and NaY zeolite was synthesized using sol-gel method. Powder XRD patterns confirmed that structures were ZSM-5 and NaY zeolites. Surface area analysis using BET method are 472,27 m2/g with pore size 2,32 nm for mesoporous ZSM-5 and 392,81 m2/g with pore size 1,6 nm for microporous NaY zeolite. NaY/ZSM-5/IDC and Cu/NaY/ZSM-5/IDC prior ammonia gas sensor testing using Electrochemical Impedance Spectroscopy (EIS) method. The composite has different sensitivity in range concentration of ammonia 0-300 ppm. The Cu/NaY/ZSM5/IDC has higher sensitivity compared to NaY/ZSM5/IDC.

  9. Separating methane emissions from biogenic sources and natural gas by vertical column enhancements of ammonia, ethane, and methane in the Colorado Front Range

    Science.gov (United States)

    Chiu, R.; Volkamer, R. M.; Blumenstock, T.; Hase, F.; Hannigan, J. W.; Kille, N.; Frey, M.; Kumar Sha, M.; Orphal, J.

    2015-12-01

    Methane sources in the Colorado Front Range include biogenic sources from cattle feedlots and natural gas operations. Although numerous studies have measured methane emissions, there remains significant uncertainty regarding the relative contributions of these various methane emission sources. Here we present data from a March 2015 field campaign that deployed two Bruker EM27 Sun Fourier Transform Spectrometers (FTS) and the University of Colorado Solar Occultation Flux (CU-SOF) FTS in Eaton, Colorado; the former were used to measure enhancements in the methane vertical column densities (VCD), while the latter was used to measure ethane and ammonia VCDs. A third EM27 FTS was deployed to a background site in Westminster, Colorado which was far removed from cattle and petroleum operations. Northerly winds make possible the determination of methane VCD column enhancement from Westminster to Eaton. All instruments were compared during several background days at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. This presentation explores the potential of methane source attribution using ammonia as a tracer for feedlot emissions and ethane as a tracer for petroleum emissions.

  10. Industrial ammonia absorption refrigeration plants in combination with gas engines; Groupes de refrigeration industriels a absorption d'ammoniac combines avec des moteurs a gaz

    Energy Technology Data Exchange (ETDEWEB)

    Bassols, J. [Colibri bv (Netherlands); Sahu, J. [Gas Natural SDG, S.A. (Spain)

    2000-07-01

    In many industrial sectors, co-generation systems with gas turbines or engines and ammonia absorption refrigeration plants are being introduced for the simultaneous production of electricity and refrigeration in order to meet the energy requirements inherent to each process and to reduce the operating costs. The different possibilities to link the absorption refrigeration plant to the cogeneration system and to the consumers are described. Different examples of realised projects are used to illustrate the different systems. Despite the fact that, compared to compression refrigeration machines, ARP's have lower COP (coefficient of performance) and higher investment costs, the advantage of using thermal energy as a driving energy instead of electricity makes the combination cogeneration-ARP very attractive. The plants can easily be integrated into an existing refrigeration installation. The full automatic control systems provide a trouble-free operation. Because most of the components of an ARP are heat exchangers, the plants only need little maintenance and are not susceptible to trouble. For their maintenance, no special knowledge is necessary. Plants working with NH{sub 3}-H{sub 2}O use ammonia as a refrigerant, which is a natural and environment-friendly fluid. (authors)

  11. Application of a miniaturized photoacoustic cell for high-sensitivity laser detection of ammonia in gas media

    CERN Document Server

    Gorelik, A V

    2008-01-01

    We present a photoacoustic resonant cell, the internal volume of which is ~ 0.5 cm^3. The cavity shape of the cell is so adapted in order to minimize the background signal arising due to absorption of laser beam in the cell windows. An experimental setup, measurement procedure and design of the cell are described. Results of detection of ammonia in nitrogen flow with the help of a CO2-laser are represented. The minimal detectable absorption for the cell is estimated in the experiment to be ~ 5.1 cm^(-1) W Hz^(-1/2)

  12. Influence of gas-particle partitioning on ammonia and nitric acid fluxes above a deciduous forest in the Midwestern USA

    DEFF Research Database (Denmark)

    Hansen, Kristina; Sørensen, Lise Lotte; Hornsby, Karen E.

    Quantifying the atmosphere-biosphere exchange of reactive nitrogen gasses (including ammonia (NH3) and nitric acid (HNO3)) is crucial to assessing the impact of anthropogenic activities on natural and semi-natural ecosystems. However, measuring the deposition of reactive nitrogen is challenging due...... are measured above the deciduous forest, Morgan Monroe State Forest (MMSF) in south-central Indiana (39°53’N, 86°25’W) during a field campaign. Two relaxed eddy accumulation (REA) systems are used to measure fluxes and concentrations of NH3 and HNO3 at 44 m. The NH3 REA system operates based on wet effluent...

  13. Growth and toxic gas sensing properties of poly(urethaneimide) thin films.

    Science.gov (United States)

    Youssef, Ismail Ben; Sarry, Frederic; Nysten, Bernard; Alexieva, Gergana; Strashilov, Vesselin; Kolev, Iliyan; Alem, Halima

    2016-06-01

    In this work we present a study on the growth and the gas sensing properties of poly(urethane imide) thin films. We first deeply characterized by atomic force microscopy (AFM) the nanostructuration of the poly(urethane imide) holding different amine groups. We further studied the interaction between highly toxic gases such as hexamethyleneimine (HMI) and pyridine and the polymer by using an unconventional method based on Quartz Crystal Microbalance (QCM) measurement. We showed for the first time that weak interactions, i.e. hydrogen bonding between the gas molecules and the polymer film allow the diffusion of the gas molecule deep in the polymeric film and the recovery of the film once the gas molecules leave the sensor. This first work paves a new way for the design of a completely recoverable sensor able to detect highly toxic gases for environmental concern.

  14. Superior selectivity and sensitivity of blue phosphorus nanotubes in gas sensing applications

    KAUST Repository

    Montes Muñoz, Enrique

    2017-05-23

    On the basis of first principles calculations, we study the adsorption of CO, CO2, NH3, NO, and NO2 molecules on armchair and zigzag blue phosphorus nanotubes. The nanotubes are found to surpass the gas sensing performance of other one-dimensional materials, in particular Si nanowires and carbon nanotubes, and two-dimensional materials, in particular graphene, phosphorene, and MoS2. Investigation of the energetics of the gas adsorption and induced charge transfers indicates that blue phosphorus nanotubes are highly sensitive to N-based molecules, in particular NO2, due to covalent bonding. The current–voltage characteristics of nanotubes connected to Au electrodes are derived by the non-equilibrium Green\\'s function formalism and used to quantitatively evaluate the change in resistivity upon gas adsorption. The observed selectivity and sensitivity properties make blue phosphorus nanotubes superior gas sensors for a wide range of applications.

  15. 以氨为碱源的焦炉煤气脱硫工艺%Coke oven gas desulfurization technology taking ammonia as alkali source

    Institute of Scientific and Technical Information of China (English)

    管福征; 陈夏; 朱建梅

    2014-01-01

    介绍了以煤气中氨为碱源,OMC-对苯二酚为催化剂的湿法脱硫工艺。生产实践表明,该工艺不但脱硫脱氰效率高,而且无废液产生,是一种清洁生产工艺。%This paper describes the wet desulfurization technology taking ammonia,which is contained in the gas,as alkali source and OMC-hydroquinone as catalyst.Production practice shows that this technology is very effective in desulfurization,and produces no wastewater.It is a clean production technology.

  16. Transport properties of the two-dimensional electron gas in GaN/AlGaN heterostructures grown by ammonia molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Pogosov, A.G.; Budantsev, M.V.; Lavrov, R.A.; Mansurov, V.G.; Nikitin, A.Yu.; Preobrazhenskii, V.V.; Zhuravlev, K.S. [Institute of Semiconductor Physics, 13 Lavrentiev Avenue, 630090 Novosibirsk (Russian Federation)

    2006-07-15

    Transport properties of the two-dimensional electron gas in AlGaN/GaN heterostructures grown by ammonia molecular-beam epitaxy are experimentally investigated. Conventional Hall and Shubnikov-de Haas measurements as well as investigations of quantum transport phenomena are reported. It is found that negative magnetoresistance (NMR) caused by weak localization demonstrates an unusual behavior at low temperature (1.8 K). The observed NMR cannot be described by the ordinary theory of quantum corrections to conductivity based on a single phase breaking time {tau}{sub {phi}}. The anomalous NMR behavior can be explained by the presence of two occupied quantum subbands, characterized by their own phase breaking times {tau} {sub {phi}} {sub 1} and {tau} {sub {phi}} {sub 2}. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Influence of AlN Buffer Thickness on GaN Grown on Si(111) by Gas Source Molecular Beam Epitaxy with Ammonia

    Institute of Scientific and Technical Information of China (English)

    LIN Guo-Qiang; ZENG Yi-Ping; WANG Xiao-Liang; LIU Hong-Xin

    2008-01-01

    Hexagonal GaN is grown on a Si(111) substrate with AlN as a buffer layer by gas source molecular beam epitaxy(GSMBE) with ammonia. The thickness of AlN buffer is changed from 9 to 72nm. When the thickness of AlN buffer is 36nm, the surface morphology and crystal quality of GaN is optimal. The in-situ reflection high energy electron diffraction (RHEED) reveals that the transition to a two-dimensional growth mode of AlN is the key to the quality of GaN. However, the thickness of AlN buffer is not so critical to the residual in-plane tensile stress in GaN grown on Si(111) by GSMBE for AlN thickness between 9 to 72nm.

  18. Microstructure and gas-sensing properties of sol-gel ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Musat, V. [Department of Metals and Materials Science, ' Dunarea de Jos' University of Galati, 800008 Galati (Romania)], E-mail: viorica.musat@ugal.ro; Rego, A.M. [Department of Chemical and Biological Engineering, CQFM, Technical University of Lisbon, 1049-001 Lisbon (Portugal); Monteiro, R.; Fortunato, E. [Department of Materials Science, CENIMAT, Faculty of Sciences and Technology, New University of Lisbon, Campus da Caparica, 2829-516 Caparica (Portugal)

    2008-02-15

    The paper presents the properties of zinc oxide thin films deposited on glass substrate via dip-coating technique. Zinc acetate dehydrate, ethanol and monoethanol amine were used as starting materials and N{sub 2} gas was used as thermal annealing atmosphere for film crystallization. The effect of withdrawal speed on the crystalline structure, morphology, zinc and nitrogen chemical states, optical, electrical and gas-sensing properties of the thin films has been investigated using X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, optical transmittance and photoreduction-ozone reoxidation data.

  19. Gas sensing properties of branched carbon nanotube-based structures using a novel low voltage emission.

    Science.gov (United States)

    Darbari, S; Azimi, S; Abdi, Y; Mohajerzadeh, S

    2012-11-01

    Branched carbon nanostructures have been successfully grown on interdigital comb-like structures for a gas sensing application. Field emission scanning electron microscopy has been utilized to investigate the morphology and structure of the grown nanostructures at different stages of growth process. Tunneling current of the fabricated sensor has been measured when a monotonically increasing voltage is applied between the electrodes. The effect of exposure to three different gases on the measured current has been studied. A data processing on the measured current voltage characteristics results in the evolution of various peaks at distinct voltages which depends on the type of the gas.

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

    OpenAIRE

    2010-01-01

    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 ...

  1. Metal Organic Framework-Metal Oxide Composites for Toxic Gas Adsorption and Sensing

    Science.gov (United States)

    2014-05-01

    TICs, they tested sulfur dioxide, ammonia, chlorine , tetrahydrothiophene, benzene, dichloromethane, and ethylene oxide. Their test MOFs included...IRMOF-3, an amine functionalized MOF, performed best against ammonia and chlorine , outperforming BPL carbon by 105 and 1.76 times, respectively. The... chlorine and ammonia, and IRMOF-62 in ammonia.88 Simple color changes provide an indicator to the extent of penetration of the adsorbent bed and

  2. Tin Oxide Nanoparticles Produced by Spark Ablation: Synthesis and Gas Sensing Properties

    Directory of Open Access Journals (Sweden)

    Alexey Efimov

    2016-12-01

    Full Text Available The synthesis parameters and results of investigation of gas sensing properties of tin oxide nanoparticles produced by spark ablation are presented. The nanoparticles have sizes below 30 nm and their specific surface area is about 40 m2/g. In order to study the gas sensing properties, a special structure comprising heater, barrier layers and contact pads was utilized. The resistance of the sensor fabricated on the basis of this structure was measured at different concentrations of hydrogen in the air (100–500 ppm and different values of relative humidity (30–80%. At working temperature of 450°C, 100 ppm of hydrogen triggers more than 8-times decrease in the sensor resistance within the time interval of about 1 s. At the same time, the humidity variation does not have pronounced effect on the sensor resistance: less than 30% in the humidity range studied.

  3. Preparation and Gas-Sensing Properties of NdFeO3 Nanocrystalline

    Institute of Scientific and Technical Information of China (English)

    牛新书; 杜卫民; 杜卫平; 蒋凯

    2003-01-01

    With the Nd2O3, Fe(NO3)3·9H2O, nitric acid(1∶1 vloume fraction) for the starting materials, rare earth composite oxide NdFeO3 with the structure of perovskite type was synthesized by sol-gel method in the system of citric acid. Structural characteristics were characterized by XRD and TEM which indicate that the sample is nanocrystallite with uniform grain size distribution and the a verage grain size is about 28 nm. Moreover, the gas sensing properties of the material were tested. The results show that NdFeO3 sensors have high sensitivity, excellent selectivity and quick response and recovery behavior to H2S, hence, this gas sensing material has a better prospects in industrial practice.

  4. Electrical and gas sensing investigations on the sprayed ZnO:Cu thin films

    Science.gov (United States)

    Mhamdi, A.; Alkhalifah, Menea S.; Rajeh, S.; Labidi, A.; Amlouk, M.; Belgacem, S.

    2017-09-01

    The electrical and gas sensing properties of the sprayed Cu doped ZnO thin layers were investigated. The main study is an analysis of the conduction mechanism based on the measurement results of the frequency dispersion of the conductivity at different temperatures performed by impedance spectroscopy. It emerges from this study that the transport mechanism of charge carriers in such thin films is a thermally activated hopping mechanism. This process is confirmed by the obtained values of the maximum barrier height Wm deduced from the study of the frequency power law of the ac conductivity. Otherwise, we have studied the response evolution of ZnO: Cu sensors ethanol versus time, working temperature and relative doping. From the measurement results of gas sensing properties of ZnO:Cu thin film, we find that a good stability and response was observed for a doping of 2%.

  5. Zigzag GaN/Ga2O3 heterogeneous nanowires: Synthesis, optical and gas sensing properties

    Directory of Open Access Journals (Sweden)

    Li-Wei Chang

    2011-09-01

    Full Text Available Zigzag GaN/Ga2O3 heterogeneous nanowires (NWs were fabricated, and the optical properties and NO gas sensing ability of the NWs were investigated. We find that NWs are most effective at 850 °C at a switching process once every 10 min (on/off = 10 min per each with a mixture flow of NH3 and Ar. The red shift of the optical bandgap (0.66 eV is observed from the UV-vis spectrum as the GaN phase forms. The gas sensing characteristics of the developed sensor are significantly replaced to those of other types of NO sensors reported in literature.

  6. Ethanol gas sensing by Zn-doped CdS/CdTe nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Prabhu, M., E-mail: prabhumku@gmail.com; Manikandan, V. S.; Soundararajan, N.; Ramachandran, K. [School of Physics, Madurai Kamaraj University, Madurai – 625 021 (India)

    2016-05-23

    Zn-doped CdS/CdTe nanoparticles (NPs) were synthesized and studied here for gas sensing. The crystallographic properties of the samples were studied by X-ray diffraction (XRD), which shows cubic structure for CdS and CdTe NPs. The three longitudinal optical phonon modes at 298, 595 and 895 cm{sup −1} were obtained from Raman spectrum and this also reveals the cubic structure of CdS NPs. The band gap for Zn-doped CdS/CdTe NPs increased slightly when compared with pure sample. The ethanol gas sensing in CdS/CdTe NPs shows an enhancement on Zn substitution.

  7. Exploring silver ionic liquids for reaction-based gas sensing on a quartz crystal microbalance.

    Science.gov (United States)

    Li, Hsin-Yi; Hsu, Tzu-Hsuan; Chen, Chien-Yuan; Tseng, Ming-Chung; Chu, Yen-Ho

    2015-09-21

    Reaction-based, sensitive sensing of aldehyde and ketone gases in real time was effectively achieved on QCM chips thin-coated with silver ionic liquids and , respectively. The method platform developed in this work involves straightforward synthesis of functional silver ionic liquids in water, and is label-free and highly chemoselective with superior gas reactivity for and and, most significantly, totally insensitive to moisture.

  8. Palladium Nanoribbon Array for Fast Hydrogen Gas Sensing with Ultrahigh Sensitivity.

    Science.gov (United States)

    Pak, Yusin; Lim, Namsoo; Kumaresan, Yogeenth; Lee, Ryeri; Kim, Kihyeun; Kim, Tae Heon; Kim, Sang-Mook; Kim, Jin Tae; Lee, Heon; Ham, Moon-Ho; Jung, Gun-Young

    2015-11-18

    A lithographically aligned palladium nano-ribbon (Pd-NRB) array with gaps of less than 40 nm is fabricated on a poly(ethylene terephthalate) substrate using the direct metal transfer method. The 200 μm Pd-NRB hydrogen gas sensor exhibits an unprecedented sensitivity of 10(9) % after bending treatment, along with fast sensing behavior (80% response time of 3.6 s and 80% recovery time of 8.7 s) at room temperature.

  9. Application technique and slurry co-fermentation effects on ammonia, nitrous oxide, and methane emissions after spreading: II. Greenhouse gas emissions.

    Science.gov (United States)

    Wulf, S; Maeting, M; Clemens, J

    2002-01-01

    The aim of this study was to investigate the effect of different application techniques on greenhouse gas emission from co-fermented slurry. Ammonia (NH3), nitrous oxide (N2O), and methane (CH4) emissions were measured in two field experiments with four different application techniques on arable and grassland sites. To gather information about fermentation effects, unfermented slurry was also tested, but with trail hose application only. Co-fermented slurry was applied in April at a rate of 30 m3 ha(-1). Measurements were made every 4 h on the first day after application and were continued for 6 wk with gradually decreasing sampling frequency. Methane emissions were application and are discussed in the preceding paper. We evaluated the climatic relevance of the measured gas emissions from the different application techniques based on the comparison of CO2 equivalents. It was evident that NH3 emission reduction, which can be achieved by injection, is at least compensated by increased N2O emissions. Our results indicate that on arable land, trail hose application with immediate shallow incorporation, and on grassland, trail shoe application, bear the smallest risks of high greenhouse gas emissions when fertilizing with co-fermented slurry.

  10. Gas-liquid absorption reaction between (NH{sub 4}){sub 2}SO{sub 3} solution and SO{sub 2} for ammonia-based wet flue gas desulfurization

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Xiang; Ding, Honglei; Du, Zhen; Fang, Mengxiang; Luo, Zhongyang; Cen, Kefa [State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027 (China); Wu, Zuliang [Department of Environmental Engineering, Zhejiang Gongshang University, Hangzhou 310035 (China)

    2010-08-15

    In order to investigate the characteristics of the reaction between ammonium sulfite, the main desulfurizing solution, and the flue-gas-contained sulfur dioxide during the process of ammonia-based WFGD (wet flue gas desulfurization) in a power plant, the gas-liquid absorption reaction between sulfur dioxide and an ammonium sulfite solution was studied in a stirred tank reactor. The experimental results indicate that the absorption of sulfur dioxide is controlled by both the gas- and liquid-films when the ammonium sulfite concentration is lower than 0.05 mol/L, and mainly by the gas-film at higher concentrations. In the latter case, the reaction rates are found to be zero-order with respect to the concentration of ammonium sulfite. The absorption rates of sulfur dioxide increase as the concentration of sulfur dioxide in inlet gas and the temperature increase. The reaction rate is of 0.6th-order with respect to the concentration of sulfur dioxide. (author)

  11. Facile synthesis of porous ZnO microbelts and analysis of their gas-sensing property

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jiarui, E-mail: jrhuang@mail.anhu.edu.cn; Shi, Chengcheng; Fu, Guijun; Sun, Pingping; Wang, Xinyue; Gu, Cuiping, E-mail: cpgu2008@mail.ahnu.edu.cn

    2014-04-01

    Porous ZnO microbelts were achieved using a facile chemical solution method combined with subsequent calcination. The micro-nanostructures were characterized through X-ray diffraction, field emission scanning electron microscopy, thermogravimetric-differential thermal analysis, and Brunauer–Emmett–Teller N{sub 2} adsorption-desorption analyses, among others. The BET surface area of the porous ZnO microbelts was calculated at 23.0 m² g{sup −1}. Furthermore, the gas sensing properties of the as-prepared porous ZnO microbelts were investigated using volatile organic compounds. Compared with ZnO microflowers, the porous ZnO microbelts exhibited higher response with certain organic vapors, such as formaldehyde, acetone, and ethanol. The responses to 100 ppm formaldehyde, acetone, and ethanol were 45.7, 40.6, and 38.4, respectively, at a working temperature of 300 °C. The results showed that the porous ZnO microbelts are highly promising candidates for gas sensing applications. - Highlights: • Zinc glycinate monohydrate microwires were obtained by a chemical solution method. • Porous ZnO microbelts were achieved after calcinations. • The porous ZnO microbelts exhibit superior gas-sensing property.

  12. Effect of gas sensing properties by Sn-Rh codoped ZnO nanosheets

    Science.gov (United States)

    Chen, Ziwei; Lin, Zhidong; Xu, Mengying; Hong, Yuyuan; Li, Na; Fu, Ping; Chen, Ze

    2016-05-01

    The hierarchically porous Sn-Rh codoped ZnO, Sn-doped ZnO and pure ZnO nanosheets have been successfully synthesized through a simple hydrothermal reaction process without any surfactant or template at 180°C. The morphology and composition were carefully characterized by X-ray diffraction, energy dispersive X-ray spectrometer, field emission scanning electronic microscopy and BET. The gas-sensing testing results indicated that the Sn-Rh codoped ZnO nanosheets, with the specific surface area was 26.9 m2/g, exhibited enhanced gas-sensing performance compared with that of pure ZnO and Sn-doped ZnO. The high sensitivity of the sensor based on Sn-Rh codoped ZnO was 149.38 to 100 ppm ethanol and the detection limit was less than 5 ppm (5.8). The response and recovery times were measured to be ˜3 s and ˜10 s when exposed to 100 ppm ethanol at the test temperature of 300°C. The good sensing performance of the Sn-Rh codoped ZnO sensor indicated that hierarchically porous Sn-Rh codoped ZnO could be a promising candidate for highly sensitive gas sensors. [Figure not available: see fulltext.

  13. Ethanol gas sensing properties of Al2O3-doped ZnO thick film resistors

    Indian Academy of Sciences (India)

    D R Patil; L A Patil; D P Amalnerkar

    2007-12-01

    The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films of Al2O3 (1 wt%) doped ZnO were observed to be highly sensitive to ethanol vapours at 300°C. Aluminium oxide grains dispersed around ZnO grains would result into the barrier height among the grains. Upon exposure of ethanol vapours, the barrier height would decrease greatly leading to drastic increase in conductance. It is reported that the surface misfits, calcination temperature and operating temperature can affect the microstructure and gas sensing performance of the sensor. The efforts are, therefore, made to create surface misfits by doping Al2O3 into zinc oxide and to study the sensing performance. The quick response and fast recovery are the main features of this sensor. The effects of microstructure and additive concentration on the gas response, selectivity, response time and recovery time of the sensor in the presence of ethanol vapours were studied and discussed.

  14. On Development and Characterisation of a Mobile and Metrologically Traceable Reference Gas Generator for Ammonia and Other Reactive Species in Ambient Air Levels

    Science.gov (United States)

    Leuenberger, Daiana; Pascale, Céline; Guillevic, Myriam; Ackermann, Andreas; Niederhauser, Bernhard

    2016-04-01

    Ammonia NH3 in the atmosphere is the major precursor for neutralising atmospheric acids and is thus affecting not only the long-range transport of sulphur dioxide and nitrogen oxides but also stabilies secondary particulate matter. These aerosols have negative impacts on air quality and human health. Moreover, they negatively affect terrestrial ecosystems after deposition. NH3 has been included in the air quality monitoring networks and emission reduction directives of European nations. Atmospheric concentrations are in the order of 0.5-500 nmol/mol. However, the lowest substance amount fraction of available certified reference material (CRM) is 30 μmol/mol. The EMRP JRP ENV55 MetNH3 aims at overcoming this discrepancy by assessing and developing novel approaches for the production of CRM and measurement methods. The Federal Institute of Metrology METAS has developed a mobile and metrologically traceable reference gas generator for reactive gases (ReGaS1). This device is based on the specific temperature dependent permeation of the reference substance through a membrane into a flow of carrier gas and subsequent dynamic dilution to desired amount fractions. The characteristics of individual components lead to the uncertainty estimation for the generated NH3 gas mixture according to GUM, which is aimed to be <3 %. Here we present insights into the development of said instrument and results of the first performance tests. Moreover, we include results of the study on adsorption/desorption effects in dry as well as humidified matrix gas into the discussion on the generation of reference gas mixtures.

  15. Synergistic improvement of gas sensing performance by micro-gravimetrically extracted kinetic/thermodynamic parameters

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Shuanbao; Xu, Pengcheng; Yu, Haitao; Cheng, Zhenxing; Li, Xinxin, E-mail: xxli@mail.sim.ac.cn

    2015-03-10

    Highlights: • Sensing material can be comprehensively optimized by using gravimetric cantilever. • Kinetic-thermodynamic model parameters are quantitatively extracted by experiment • Sensing-material performance is synergistically optimized by extracted parameters. - Abstract: A novel method is explored for comprehensive design/optimization of organophosphorus sensing material, which is loaded on mass-type microcantilever sensor. Conventionally, by directly observing the gas sensing response, it is difficult to build quantitative relationship with the intrinsic structure of the material. To break through this difficulty, resonant cantilever is employed as gravimetric tool to implement molecule adsorption experiment. Based on the sensing data, key kinetic/thermodynamic parameters of the material to the molecule, including adsorption heat −ΔH°, adsorption/desorption rate constants K{sub a} and K{sub d}, active-site number per unit mass N′ and surface coverage θ, can be quantitatively extracted according to physical–chemistry theories. With gaseous DMMP (simulant of organophosphorus agents) as sensing target, the optimization route for three sensing materials is successfully demonstrated. Firstly, a hyper-branched polymer is evaluated. Though suffering low sensitivity due to insufficient N′, the bis(4-hydroxyphenyl)-hexafluoropropane (BHPF) sensing-group exhibits satisfactory reproducibility due to appropriate −ΔH°. To achieve more sensing-sites, KIT-5 mesoporous-silica with higher surface-area is assessed, resulting in good sensitivity but too high −ΔH° that brings poor repeatability. After comprehensive consideration, the confirmed BHPF sensing-group is grafted on the KIT-5 carrier to form an optimized DMMP sensing nanomaterial. Experimental results indicate that, featuring appropriate kinetic/thermodynamic parameters of −ΔH°, K{sub a}, K{sub d}, N′ and θ, the BHPF-functionalized KIT-5 mesoporous silica exhibits synergistic

  16. 40 A Platinum-porous SiC gas sensor: Investigation sensing properties of H{sub 2} gas

    Energy Technology Data Exchange (ETDEWEB)

    Keffous, A., E-mail: keffousa@yahoo.fr [Centre de Recherche en Technologie des Semiconducteurs pourl' energetique (CRTSE), 02Bd, Frantz Fanon, B.P. 140, Algiers (Algeria); Cheriet, A.; Hadjersi, T.; Boukennous, Y.; Gabouze, N.; Boukezzata, A.; Belkacem, Y. [Centre de Recherche en Technologie des Semiconducteurs pourl' energetique (CRTSE), 02Bd, Frantz Fanon, B.P. 140, Algiers (Algeria); Kechouane, M. [Houari Boumediene University (USTHB), Physical Faculty (Algeria); Kerdja, T. [Advanced Technology Center (CDTA) (Algeria); Menari, H.; Berouaken, M.; Talbi, L.; Ouadah, Y. [Centre de Recherche en Technologie des Semiconducteurs pourl' energetique (CRTSE), 02Bd, Frantz Fanon, B.P. 140, Algiers (Algeria)

    2013-01-01

    The present paper reports on a new structure for H{sub 2} gas sensing based on thin porous silicon carbide (PSiC) films. The PSiC layer has been formed by electrochemical etching of SiC films previously deposited onto p-type silicon substrate by pulsed laser deposition (PLD) using 6H-SiC target. Current-voltage (I-V) and current-time (I-t) characteristics have been measured. A thin platinum (Pt) film (40 A thickness) deposited onto PSiC layer has been used as a catalytic metal. The Schottky diode parameters such as ideality factor (n), barrier height ({phi}{sub Bp}) and series resistance (R{sub S}) have been evaluated under different concentrations of H{sub 2} gas. The experimental results show that upon exposure to H{sub 2} gas the barrier height, the ideality factor and the series resistance change significantly. The different changes in the electrical parameters of the structure (increase and decrease as a function of the H{sub 2} concentration) have been explained by the formation of two inversion layers. The first one forms as soon as the gas is in contact with the sensor and the second when the concentration reaches 90 ppm. Subsequently, the effect of gas concentration on the maximum sensitivity value of the sensor has been investigated. A high sensitivity ({Delta}I/I) value around 86% is found at about 1 V bias voltage. In addition, the response and recovery times were determined to be around 55 s and 160 s, respectively. Finally, the structure shows a reversible response for low gas concentration at room temperature.

  17. Three-dimensional conductive networks based on stacked SiO2@graphene frameworks for enhanced gas sensing.

    Science.gov (United States)

    Huang, Da; Yang, Zhi; Li, Xiaolin; Zhang, Liling; Hu, Jing; Su, Yanjie; Hu, Nantao; Yin, Guilin; He, Dannong; Zhang, Yafei

    2017-01-07

    Graphene is an ideal candidate for gas sensing due to its excellent conductivity and large specific surface areas. However, it usually suffers from sheet stacking, which seriously debilitates its sensing performance. Herein, we demonstrate a three-dimensional conductive network based on stacked SiO2@graphene core-shell hybrid frameworks for enhanced gas sensing. SiO2 spheres are uniformly encapsulated by graphene oxide (GO) through an electrostatic self-assembly approach to form SiO2@GO core-shell hybrid frameworks, which are reduced through thermal annealing to establish three-dimensional (3D) conductive sensing networks. The SiO2 supported 3D conductive graphene frameworks reveal superior sensing performance to bare reduced graphene oxide (RGO) films, which can be attributed to their less agglomeration and larger surface area. The response value of the 3D framework based sensor for 50 ppm NH3 and 50 ppm NO2 increased 8 times and 5 times, respectively. Additionally, the sensing performance degradation caused by the stacking of the sensing materials is significantly suppressed because the graphene layers are separated by the SiO2 spheres. The sensing performance decays by 92% for the bare RGO films when the concentration of the sensing material increases 8 times, while there is only a decay of 25% for that of the SiO2@graphene core-shell hybrid frameworks. This work provides an insight into 3D frameworks of hybrid materials for effectively improving gas sensing performance.

  18. Optical Fiber Chemical Sensor with Sol-Gel Derived Refractive Material as Transducer for High Temperature Gas Sensing in Clean Coal Technology

    Energy Technology Data Exchange (ETDEWEB)

    Shiquan Tao

    2006-12-31

    fiber optic sensors uses sol-gel derived porous silica materials doped with nanometer particles of noble metals in the form of fiber or coating for sensing trace H{sub 2}, NH{sub 3} and HCl in gas samples at for applications ambient temperature. The third classes of fiber optic sensors use sol-gel derived semiconductor metal oxide coating on the surface of silica optical fiber as transducers for selectively sensing H{sub 2}, CH{sub 4} and CO at high temperature. In addition, optical fiber temperature sensors use the fluorescence signal of rare-earth metal ions doped porous silica optical fiber or the optical absorption signal of thermochromic metal oxide materials coated on the surface of silica optical fibers have also been developed for monitoring gas temperature of corrosive gas. Based on the results obtained from this project, the principle of fiber optic sensor techniques for monitoring matrix gas components as well as trace components of coal gasification derived syngas has been established. Prototype sensors for sensing trace ammonia and hydrogen sulfide in gasification derived syngas have been built up in our laboratory and have been tested using gas samples with matrix gas composition similar to that of gasification derived fuel gas. Test results illustrated the feasibility of these sensors for applications in IGCC processes.

  19. The Electrostatically Formed Nanowire: A Novel Platform for Gas-Sensing Applications

    Directory of Open Access Journals (Sweden)

    Gil Shalev

    2017-02-01

    Full Text Available The electrostatically formed nanowire (EFN gas sensor is based on a multiple-gate field-effect transistor with a conducting nanowire, which is not defined physically; rather, the nanowire is defined electrostatically post-fabrication, by using appropriate biasing of the different surrounding gates. The EFN is fabricated by using standard silicon processing technologies with relaxed design rules and, thereby, supports the realization of a low-cost and robust gas sensor, suitable for mass production. Although the smallest lithographic definition is higher than half a micrometer, appropriate tuning of the biasing of the gates concludes a conducting channel with a tunable diameter, which can transform the conducting channel into a nanowire with a diameter smaller than 20 nm. The tunable size and shape of the nanowire elicits tunable sensing parameters, such as sensitivity, limit of detection, and dynamic range, such that a single EFN gas sensor can perform with high sensitivity and a broad dynamic range by merely changing the biasing configuration. The current work reviews the design of the EFN gas sensor, its fabrication considerations and process flow, means of electrical characterization, and preliminary sensing performance at room temperature, underlying the unique and advantageous tunable capability of the device.

  20. Investigation Into Gas-Sensing Mechanism of Nanostructured Magnesium Aluminate as a Function of Temperature.

    Science.gov (United States)

    Nithyavathy, N; Arunmetha, S; Dhineshbabu, N R; Rajendran, V

    2015-07-01

    In this study, we used a new simple chemical method to synthesise nanostructured magnesium aluminate (NMA) powder. Sol-gel technique followed by sonication was used to develop different sensor samples namely NMA573, NMA873, and NMA1 073 by calcination at temperatures of 573, 873, and 1073 K respectively. Average crystallite size of 18-27 nm and specific surface area of 68.09 to 61.84 m2 g(-1) was obtained for the sensor samples. The existence of functional groups at 800 and 550 cm-1 corresponding respectively to AIO6 group and the lattice vibration of MgO4 stretching were confirmed through FTIR studies; SEM/EDX confirm the spherical morphology with elemental composition Mg, Al and O at different calcination temperatures. UV-Vis absorption spectra show band gap energy as 3.50, 3.48, and 3.44 eV for the sensor samples NMA573, NMA873, and NMA1 073 respectively. The effect of polyethylene glycol on the gas-sensing behaviour was studied in all the sensor samples. In particular, NMA1073 was found to have better resistance and sensor response for CO gas than NMA573 and NMA873. The effect of increase in calcination temperature of the sensor samples on the structural, morphological, optical, and gas response properties were carried out extensively to explore its gas sensing applications.

  1. A vertical tip-tip contact silicon nanowire array for gas sensing.

    Science.gov (United States)

    Lin, Leimiao; Liu, Dong; Chen, Qiaofen; Zhou, Hongzhi; Wu, Jianmin

    2016-10-20

    Novel chemiresistive gas sensors based on a vertical tip-tip contact silicon nanowire (TTC-SiNW) array were constructed. The welding of TTC-SiNWs after joule heating treatment was confirmed by a current-voltage curve (I-V curve). The TTC-SiNW structure not only resolved the problem of electrode contact encountered in conventional nanowire sensors, but also elongated the nanowire length to increase the void space for fast gas diffusion. The TTC-SiNW sensor comprising the same two types of SiNW arrays responded to NO2 very sensitively. The LOD for the p-p and n-n contact SiNW arrays is around 150 ppb and 3 ppb (S/N = 3), respectively. Furthermore, the highly oriented nano-junction formed on the TTC structure provided solid evidence to clarify the contribution of the nanojunction to gas sensing behavior. The TTC-SiNW sensor with a p-n junction displays a significant rectification effect. The sensitive response towards NO2 (LOD is about 18 ppb) was observed at a reverse bias voltage, whereas the response at a forward bias voltage was insignificant. Finally, the mechanism of gas sensing behavior on different types of TTC structures was proposed.

  2. Integrated Wavelength-Tunable Light Source for Optical Gas Sensing Systems

    Directory of Open Access Journals (Sweden)

    Bin Li

    2015-01-01

    Full Text Available A compact instrument consisting of a distributed feedback laser (DFB at 1.65 μm was developed as a light source for gas sensing systems using tunable diode laser absorption spectroscopy (TDLAS technique. The wavelength of laser is tuned by adjusting the laser working temperature and injection current, which are performed by self-developed temperature controller and current modulator respectively. Stability test shows the fluctuation of the laser temperature is within the range of ±0.02°C. For gas detection experiments, the wavelength is tuned around the gas absorption line by adjusting laser temperature and is then shifted periodically to scan across the absorption line by the laser current modulator, which generates a 10 Hz saw wave signal. In addition, the current modulator is able to generate sine wave signal for gas sensing systems using wavelength modulation spectroscopy (WMS technique involving extraction of harmonic signals. The spectrum test proves good stability that the spectrum was measured 6 times every 10 minutes at the constant temperature and current condition. This standalone instrument can be applied as a light source for detection systems of different gases by integrating lasers at corresponding wavelength.

  3. Reduced Graphene Oxide Mediated SnO2 Nanocrystals for Enhanced Gas-sensing Properties

    Institute of Scientific and Technical Information of China (English)

    Yanhong Chang; Yunfeng Yao; Bin Wang; Hui Luo; Tianyi Li; Linjie Zhi

    2013-01-01

    SnO2-reduced graphene oxide (SnO2-rGO) composites were prepared via a hydro-thermal reaction of graphene oxide (GO) and SnCl2·2H2O in the mixed solvent of ethylene glycol and water.During the redox reaction,GO was reduced to rGO while Sn2+ was oxidized to SnO2,uniformly depositing on the surface of rGO sheets.The composites were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),thermogravimetric analysis (TGA),infrared spectra analysis (IR) and transmission electron microscopy (TEM),respectively,and their gas sensing properties were further investigated.Compared with pure SnO2 nanoparticles,the as-prepared SnO2-rGO gas sensor showed much better gas sensing behavior in sensitivity and response-recovery time to ethanol and H2S at low concentrations.Overall,the highly sensitive,quickresponding and low cost SnO2-rGO gas sensor could be potentially applied in environmental monitoring area.

  4. Terahertz gas sensing based on a simple one-dimensional photonic crystal cavity with high-quality factors

    DEFF Research Database (Denmark)

    Chen, T.; Han, Z. H.; Liu, J. J.

    2014-01-01

    exhibits high-quality factors, facilitating the realization of high sensitivity in the gas refractive index sensing. In our experiment, 6% of the change of hydrogen concentration in air, which corresponds to a refractive index change of 1.4 x 10(-5), can be steadily detected, and different gas samples can......We report in this paper terahertz gas sensing using a simple 1D photonic crystal cavity. The resonant frequencies of the cavity depend linearly on the refractive index of the ambient gas, which can then be measured by monitoring the resonance shift. Although quite easy to manufacture, this cavity...

  5. Surface Acoustic WaveAmmonia Sensors Based on ST-cut Quartz under Periodic Al Structure

    Directory of Open Access Journals (Sweden)

    Ming-Yau Su

    2009-02-01

    Full Text Available Surface acoustic wave (SAW devices are key components for sensing applications. SAW propagation under a periodic grating was investigated in this work. The theoretical method used here is the space harmonic method. We also applied the results of SAW propagation studied in this work to design a two-port resonator with an Al grating on ST-cut quartz. The measured frequency responses of the resonator were similar to the simulation ones. Then, the chemical interface of polyaniline/WO3 composites was coated on the SAW sensor for ammonia detection. The SAW sensor responded to ammonia gas and could be regenerated using dry nitrogen.

  6. In situ gas sensing using a remotely detectable probe with replaceable insert.

    Science.gov (United States)

    Lim, Sun Do; Ma, Kyungsik; Jeong, Ji Ho; Kim, Gilhwan; Lee, Kwanil; Jeong, Je-Myung; Lee, Sang Bae

    2012-01-16

    We demonstrate a spectroscopic gas sensor using an optical fiber probe with a replaceable insert. The probe consists of a hollow-core photonic bandgap fiber (HC-PBGF) with a core diameter of 10.9 μm and a glass tube where a 2-μm hollow core fiber (HCF) with a gold coated end facet can be inserted. The HCF is designed to function as both a gate where gases can enter the HC-PBGF and a mirror reflecting the guided light back to the HC-PBGF. The opposite distal end of the probe is also designed to be able to regulate the gas pressure within the HC-PBGF for a high gas flow rate, while still transmitting the reflected light to the analysis instrument. The remote sensing probe, we believe, has much potential for detecting gases in hazardous environments.

  7. Chlorine sensing properties of zinc oxide resistive gas sensor doped with platinum

    Science.gov (United States)

    Fiedot, M.; Suchorska-Woźniak, P.; Rac, O.; Nawrot, W.; Teterycz, H.

    2016-11-01

    In presented studies resistive chlorine gas sensor with gas sensitive layer in the form of zinc oxide microrods doped with platinum was developed. The growth of active layer was carried out in water solution containing zinc nitrate (V), hexamethylenetetramine and chloroplatinic acid using the chemical bath deposition method. The structure and morphology of obtained sensors was characterized by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX). To determine the chlorine gas sensing properties Temperature-Stimulated Conductance method (TSC) was used. During the measurements sensor was tested in a reference atmosphere and an atmosphere with 2, 5 or 8 ppm of chlorine. Obtained results have shown that zinc oxide microrods doped with platinum were obtained. TSC measurements showed that developed sensor allows to detect chlorine with very good sensitivity.

  8. Preparation of magnesium hydroxide by ammonia gas method%氨气法制备氢氧化镁工艺研究

    Institute of Scientific and Technical Information of China (English)

    宋雪雪; 李丽娟; 刘志启; 时东; 姬连敏; 张波; 聂锋

    2014-01-01

    Magnesium hydroxide of high mass fraction slurry was directly synthesized without any additives,using bischofite and ammonia as raw materials.Stirring speed,mole ratio of ammonia to magnesium,ammonia gas addition rate,ageing time reaction temperature and magnesium chloride concentration were studied to find their influences to magnesium hydroxide slurry concentration and particle size.The optimum processing conditions were obtained as follows:stirring speed 350 r/min,mole ratio of ammonia to magnesium 2∶1 ,ammonia addition rate 320 mL/min,aging time 90 min,reaction temperature 60 ℃ and magnesium chloride concentration 4.30 mol/L.The effects of characterize product morphologies, structures and size distributions involved were studied through scanning electron microscope,X-ray diffractometer and laser particle analyzer.The magnesium hydroxide obtained under the optimal reaction conditions had D50 of 1 .43 μm,D90 of 2.40 μm,purity of 99.60% and whiteness of 99.34.The reaction yield reached 69.41% with magnesium hydroxide slurry mass fraction of 1 2.26%.%以水氯镁石和氨气为原料,在不加入任何添加剂的条件下,利用直接沉淀法,制备具有高料浆质量分数的氢氧化镁阻燃剂。研究了搅拌强度、氨镁摩尔比、氨气加入流量、陈化时间、反应温度、氯化镁浓度对制备氢氧化镁粒度分布以及料浆浓度的影响,确定了最佳工艺条件:搅拌强度350 r/min、氨镁摩尔比2∶1、氨气加入流量320 mL/min、陈化时间90 min、反应温度60℃、氯化镁浓度4.30 mol/L。用扫描电子显微镜、X射线衍射仪和激光粒度分布仪表征产品的形貌、结构及粒度。在最佳工艺条件下制备得到的氢氧化镁D501.43μm,D902.40μm,料浆质量分数12.26%,Mg收率69.41%,氢氧化镁纯度99.60%,白度99.34。

  9. Triboelectric-based harvesting of gas flow energy and powerless sensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Taghavi, Majid, E-mail: majid.taghavi@iit.it [Micro-BioRobotics Center, Istituto Italiano di Tecnologia, Pontedera (Italy); Biorobotics Institute, Scuola Superiore Sant’Anna, Pontedera, Pisa (Italy); Sadeghi, Ali; Mazzolai, Barbara [Micro-BioRobotics Center, Istituto Italiano di Tecnologia, Pontedera (Italy); Beccai, Lucia, E-mail: lucia.beccai@iit.it [Micro-BioRobotics Center, Istituto Italiano di Tecnologia, Pontedera (Italy); Mattoli, Virgilio, E-mail: virgilio.mattoli@iit.it [Micro-BioRobotics Center, Istituto Italiano di Tecnologia, Pontedera (Italy)

    2014-12-30

    Highlights: • The mechanical energy of both pure and impure gases can be harvested by the introduced system. • The blown gas vibrates a non conductive sheet between two surfaces, generating the triboelectric charges. • The system is able to measure the flow rate of the blown gas. • The existence of dust in the blown air can be detected without external powering. • A self powered smoke detector is introduced. - Abstract: In this work, we propose an approach that can convert gas flow energy to electric energy by using the triboelectric effect, in a structure integrating at least two conductive parts (i.e. electrodes) and one non-conductive sheet. The gas flow induces vibration of the cited parts. Therefore, the frequent attaching and releasing between a non-conductive layer with at least one electrode generates electrostatic charges on the surfaces, and then an electron flow between the two electrodes. The effect of blown gas on the output signals is studied to evaluate the gas flow sensing. We also illustrate that the introduced system has an ability to detect micro particles driven by air into the system. Finally we show how we can use this approach for a self sustainable system demonstrating smoke detection and LED lightening.

  10. Dimethylamine as a replacement for ammonia dosing in the secondary circuit of an advanced gas-cooled reactor (AGR) power station

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, Chris; Mitchell, Malcolm S. [EDF Energy, Hartlepool Power Station, Hartlepool (United Kingdom); Bull, Andrew E.A.; Quirk, Graham P.; Rudge, Andy [EDF Energy Nuclear Generation, Barnwood, Gloucester (United Kingdom). Central Technical Organisation; Woolsey, Ian S.

    2012-06-15

    Increasing flow resistance observed over recent years within the helical once-through boilers in the four advanced gas-cooled reactors at Hartlepool and Heysham 1 Power Stations have reduced boiler performance, resulting in reductions in feedwater flow, steam temperatures, and power output and in the need to carry out periodic chemical cleaning. The root cause is believed to be the development of magnetite deposits with high flow impedance in the 9Cr1Mo evaporator section of the boiler tubing. To prevent continued increases in boiler flow resistance, dimethylamine is being trialled, in one of the four affected units, as a replacement to the conventional ammonia dosing. Dimethylamine increases the pH at temperature around the secondary circuit and, based on full scale boiler rig simulations, is expected to reduce iron transport and prevent flow resistance increases within the evaporator section of the boiler. The dimethylamine plant trial commenced in January 2011 and is ongoing. The feedwater concentration of dimethylamine has been increased progressively towards a final target value of 900 {mu}g . kg{sup -1} and its effect on iron transport and boiler pressure loss is being closely monitored. The high steam temperature (> 500 C) of the secondary circuit leads to some decomposition of dimethylamine, which is being carefully monitored at various locations around the circuit. The decomposition products identified with dimethylamine dosing include ammonia, methylamine, formic acid, carbon dioxide and, as yet, unidentified neutral organic species. The effect of dimethylamine dosing on iron transport and boiler pressure drops and its decomposition behaviour around the secondary circuit during the plant trial will be presented in this paper. (orig.)

  11. Synthesis and evaluation of novel biochar-based and metal oxide-based catalysts for removal of model tar (toluene), ammonia, and hydrogen sulfide from simulated producer gas

    Science.gov (United States)

    Bhandari, Pushpak

    Gasification is a thermochemical conversion process in which carbonaceous feedstock is gasified in a controlled atmosphere to generate producer gas. The producer gas is used for production of heat, power, fuels and chemicals. Various contaminants such as tars, NH3, and H2S in producer gas possess many problems due to their corrosive nature and their ability to clog and deactivate catalysts. In this study, several catalysts were synthesized, characterized, and tested for removal of three contaminants (toluene (model tar), NH3, and H2S) from the biomass-generated producer gas. Biochar, a catalyst, was generated from gasification of switchgrass. Activated carbon and acidic surface activated carbon were synthesized using ultrasonication method from biochar. Acidic surface was synthesized by coating activated carbon with dilute acid. Mixed metal oxide catalysts were synthesized from hydrotalcite precursors using novel synthesis technique using microwave and ultrasonication. Surface area of activated carbon (˜900 m2/g) was significantly higher than that of its precursor biochar (˜60 m2/g). Surface area of metal oxide catalyst was approximately 180 m2/g after calcination. Biochar, activated carbon, and acidic surface activated carbon showed toluene removal efficiencies of approximately 78, 88, and 88 %, respectively, when the catalysts were tested individually with toluene in the presence of producer gas at 800 °C. The toluene removal efficiencies increased to 86, 91, and 97 % using biochar, activated carbon and acidic surface activated carbon, respectively in the presence of NH3 and H2S in the producer gas. Increase in toluene removal efficiencies in presence of NH3 and H2S indicates that NH3 and H 2S play a role in toluene reforming reactions during simultaneous removal of contaminants. Toluene removal efficiency for mixed metal oxide was approximately 83%. Ammonia adsorption capacities were 0.008 g NH3/g catalyst for biochar and 0.03g NH3/g catalyst for activated

  12. Synthesis, characterization and gas sensing properties of novel homo and hetero dinuclear ball-type phthalocyanines.

    Science.gov (United States)

    Kakı, Esra; Altındal, Ahmet; Salih, Bekir; Bekaroğlu, Özer

    2015-05-01

    New ball-type homodinuclear Co(ii)-Co(ii) phthalocyanine () and ball-type heterodinuclear Co(ii)-Fe(ii) phthalocyanine () were synthesized from the corresponding [2,10,16,24-tetrakis{4,4'-cyclohexylidenebis(2-cyclohexyphenoxyphthalonitrile)}phthalocyaninatocobalt(ii)] (). The novel compounds have been characterized by elemental analysis, IR, UV-Vis and MALDI-TOF mass spectroscopy. Gas sensing capability of the spin coated film of and were studied using amperometric technique at various temperatures. For a better understanding of the interaction of and films with organic compounds, two different groups of compounds (aromatics and alcohols) were selected as test analytes. It was observed that the operating temperature had a considerable effect on the gas sensing performance of the sensors investigated. The experimental results show that film offers a promising perspective as a sensing material for the detection of relatively low aromatic vapours even at room temperature. This suggests that aromatics might be distinguished from alcohols. The obtained data were analysed using two different adsorption kinetic models: the pseudo first order equation and Elovich equation to determine the best fit equation for the adsorption of toluene vapor onto and films. The first-order equation was the best of the various kinetic models studied to describe the adsorption kinetic of toluene on Pc films at higher concentrations, as evidenced by the highest correlation coefficients. In addition, it was observed that Elovich equation generates a straight line that best fit to the data of adsorption of lower concentrations of toluene.

  13. Enhancement of ammonia gas detection by integrating wavelength-modulated spectra across the line 992.69 cm-1

    Science.gov (United States)

    Dallah, Mohammad; Salloum, Akil

    2016-05-01

    A rapid tunable diode laser (TDL) absorption sensor was developed for real-time measurements of ammonia concentration by using wavelength modulation spectroscopy (WMS) at 992.698 cm-1 of the ν2 vibrational band. This line has patterns free from interference with other species in the atmosphere, and can be used for open-path detection. The 1f signal was used to normalize the 2f signal thereby eliminating the need for calibration and explaining the laser transmission variations. Using WMS with a large modulation depth and integrating the absolute value of the resulting spectra increased the limit of detection (LOD) of the sensor by a factor of seven, compared with the LOD achieved by using the maximum value of the WMS 2f signal. Furthermore, an increase by a factor of 25 compared with the direct absorption spectroscopy was achieved, which allowed obtaining LOD ∼ 1 ppb with a resolution time of <2 s for the detection of NH3 in the atmosphere using a short-path cell (a 60-cm absorption cell with four passes).

  14. Facile Synthesis and Characterizations of MOF-5 Coordination Polymer with Various Metal Linker Ratios for Ammonia Gas Storage

    Science.gov (United States)

    Misran, Halina; Aminuddin, A. M.; Zini, F. A. M.; Ghazali, M. J.; Ramesh, S.

    2011-01-01

    Metal-organic framework coordination polymer materials of MOF-5 with Fm3m cubic structure and tetrahedral structure were successfully synthesized at room temperature and pressure using liquid-crystal (i.e. surfactant) templating method and direct mixing method. The crystallinity increased as metal (Zn)/linker (benzenedicarboxylic acid, BDC) ratios were varied from 0.3 to 0.5. However, the cubic structure of evacuated framework was relatively disrupted at metal/linker ratio of 0.7. Direct-mixing synthesis approach resulted in MOF-5 with layered tetragonal structure due to the increased mobility of the organic-linker as the metal/linker ratios were increased. On the other hand, liquid-crystal templating method resulted in MOF-5 with cubic structure with sizes of ca. 3-5 micron. Changing the solvent from dimethylformamide to chloroform during the synthesis affected the size of the single cubic to decrease from 5 micron to 3 micron, respectively. Furthermore, MOF-5 prepared with metal/linker ratio 0.5 and aged in solvents with higher crystallinity exhibited higher ammonia adsorption uptake at ca. 7.2%.

  15. Evaluation of gas-sensing properties of ZnO nanostructures electrochemically doped with Au nanophases.

    Science.gov (United States)

    Dilonardo, Elena; Penza, Michele; Alvisi, Marco; Di Franco, Cinzia; Palmisano, Francesco; Torsi, Luisa; Cioffi, Nicola

    2016-01-01

    A one-step electrochemical method based on sacrificial anode electrolysis (SAE) was used to deposit stabilized gold nanoparticles (Au NPs) directly on the surface of nanostructured ZnO powders, previously synthesized through a sol-gel process. The effect of thermal annealing temperatures (300 and 550 °C) on chemical, morphological, and structural properties of pristine and Au-doped ZnO nancomposites (Au@ZnO) was investigated. Transmission and scanning electron microscopy (TEM and SEM), as well as X-ray photoelectron spectroscopy (XPS), revealed the successful deposition of nanoscale gold on the surface of spherical and rod-like ZnO nanostructures, obtained after annealing at 300 and 550 °C, respectively. The pristine ZnO and Au@ZnO nanocomposites are proposed as active layer in chemiresistive gas sensors for low-cost processing. Gas-sensing measurements towards NO2 were collected at 300 °C, evaluating not only the Au-doping effect, but also the influence of the different ZnO nanostructures on the gas-sensing properties.

  16. Influence of palladium on gas-sensing performance of magnesium ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Darshane, Sonali [Department of Physics, Solapur University, Solapur 413255 (India); National Chemical Laboratory, Pune 411008 (India); Mulla, I.S., E-mail: is.mulla@ncl.res.in [National Chemical Laboratory, Pune 411008 (India)

    2010-01-15

    Commercial ferrites with high densities are mostly used in the electromagnetic devices, which require high temperature synthesis. In this article the gas-sensing characteristics of pure and Pd-doped MgFe{sub 2}O{sub 4} powder has been discussed. The synthesis has been carried out by using a simple molten salt method. This method facilitates rapid synthesis at comparatively lower temperature enabling formation of nanostructures, suitable for the gas-sensing application. Various physicochemical techniques have been used for the characterization of samples. X-ray diffraction analysis confirmed the single-phase formation of pure and Pd-doped MgFe{sub 2}O{sub 4} having crystallite size 15-20 nm. Pure MgFe{sub 2}O{sub 4} showed highest responses towards liquid petroleum gas (LPG) at 350 deg. C while, on doping with Pd the highest response shifted towards lower operating temperature of {approx}200 deg. C. Pure MgFe{sub 2}O{sub 4} exhibited some response towards 200 ppm of LPG which markedly increased on doping of palladium (Pd). The probable mechanism is proposed to explain the selective response towards LPG.

  17. Evaluation of gas-sensing properties of ZnO nanostructures electrochemically doped with Au nanophases

    Directory of Open Access Journals (Sweden)

    Elena Dilonardo

    2016-01-01

    Full Text Available A one-step electrochemical method based on sacrificial anode electrolysis (SAE was used to deposit stabilized gold nanoparticles (Au NPs directly on the surface of nanostructured ZnO powders, previously synthesized through a sol–gel process. The effect of thermal annealing temperatures (300 and 550 °C on chemical, morphological, and structural properties of pristine and Au-doped ZnO nancomposites (Au@ZnO was investigated. Transmission and scanning electron microscopy (TEM and SEM, as well as X-ray photoelectron spectroscopy (XPS, revealed the successful deposition of nanoscale gold on the surface of spherical and rod-like ZnO nanostructures, obtained after annealing at 300 and 550 °C, respectively. The pristine ZnO and Au@ZnO nanocomposites are proposed as active layer in chemiresistive gas sensors for low-cost processing. Gas-sensing measurements towards NO2 were collected at 300 °C, evaluating not only the Au-doping effect, but also the influence of the different ZnO nanostructures on the gas-sensing properties.

  18. Micro/Nano Gas Sensors: A New Strategy Towards In-Situ Wafer-Level Fabrication of High-Performance Gas Sensing Chips

    Science.gov (United States)

    Xu, Lei; Dai, Zhengfei; Duan, Guotao; Guo, Lianfeng; Wang, Yi; Zhou, Hong; Liu, Yanxiang; Cai, Weiping; Wang, Yuelin; Li, Tie

    2015-01-01

    Nano-structured gas sensing materials, in particular nanoparticles, nanotubes, and nanowires, enable high sensitivity at a ppb level for gas sensors. For practical applications, it is highly desirable to be able to manufacture such gas sensors in batch and at low cost. We present here a strategy of in-situ wafer-level fabrication of the high-performance micro/nano gas sensing chips by naturally integrating microhotplatform (MHP) with nanopore array (NPA). By introducing colloidal crystal template, a wafer-level ordered homogenous SnO2 NPA is synthesized in-situ on a 4-inch MHP wafer, able to produce thousands of gas sensing units in one batch. The integration of micromachining process and nanofabrication process endues micro/nano gas sensing chips at low cost, high throughput, and with high sensitivity (down to ~20 ppb), fast response time (down to ~1 s), and low power consumption (down to ~30 mW). The proposed strategy of integrating MHP with NPA represents a versatile approach for in-situ wafer-level fabrication of high-performance micro/nano gas sensors for real industrial applications. PMID:26001035

  19. Application of gas-coupled laser acoustic detection to gelatins and underwater sensing

    Energy Technology Data Exchange (ETDEWEB)

    Caron, James N. [Research Support Instruments, Lanham, MD 20706, USA and Quarktet, Silver Spring, MD 20901 (United States); Kunapareddy, Pratima [Research Support Instruments, Lanham, MD 20706 (United States)

    2014-02-18

    Gas-coupled Laser Acoustic Detection (GCLAD) has been used as a method to sense ultrasound waves in materials without contact of the material surface. To sense the waveform, a laser beam is directed parallel to the material surface and displaced or deflected when the radiated waveform traverses the beam. We present recent tests that demonstrate the potential of using this technique for detecting ultrasound in gelatin phantoms and in water. As opposed to interferometric detection, GCLAD operates independently of the optical surface properties of the material. This allows the technique to be used in cases where the material is transparent or semi-transparent. We present results on sensing ultrasound in gelatin phantoms that are used to mimic biological materials. As with air-coupled transducers, the frequency response of GCLAD at high frequencies is limited by the high attenuation of ultrasound in air. In contrast, water has a much lower attenuation. Here we demonstrate the use of a GCLAD-like system in water, measuring the directivity response at 1 MHz and sensing waveforms with higher frequency content.

  20. An overview of micromachined platforms for thermal sensing and gas detection

    Energy Technology Data Exchange (ETDEWEB)

    Manginell, R.P.; Smith, J.H.; Ricco, A.J.

    1997-03-01

    Micromachined hotplates, membranes, filaments, and cantilevers have all been used as platforms for thermal sensing and gas detection. Compared with conventional devices, micromachined sensors are characterized by low power consumption, high sensitivity, and fast response time. Much of these gains can be attributed to the size reductions achieved by micromachining. In addition, micromachining permits easy, yet precise tailoring of the heat transfer characteristics of these devices. By simple alterations in device geometry and materials used, the relative magnitudes of radiation, convection and conduction losses and Joule heat gains can be adjusted, and in this way device response can be optimized for specific applications. The free-standing design of micromachined platforms, for example, reduces heat conduction losses to the substrate, thereby making them attractive as low power, fast-response heaters suitable for a number of applications. However, while micromachining solves some of the heat transfer problems typical of conventionally produced devices, it introduces some of its own. These trade-offs will be discussed in the context of several micromachined thermal and gas sensors present in the literature. These include micromachined flow sensors, gas thermal conductivity sensors, pressure sensors, uncooled IR sensors, metal-oxide and catalytic/calorimetric gas sensors. Recent results obtained for a microbridge-based catalytic/calorimetric gas sensor will also be presented as a means of further illustrating the concepts of thermal design in micromachined sensors.

  1. Design of nanocomposite film-based plasmonic device for gas sensing

    Indian Academy of Sciences (India)

    Kaushik Brahmachari; Mina Ray

    2014-07-01

    Surface plasmon resonance (SPR) is a very efficient tool for chemical and biological sensing in nanotechnology, nanobiotechnology, medicine and environmental monitoring. A theoretical simulation study incorporating the use of admittance loci design methodology in SPR-based sensing device using gold-tungsten trioxide (Au-WO3−) nanocomposite film is reported in this paper. A simple Kretschmann–Raether-type prism-based plasmonic device consisting of a glass prism, Au-WO3− nanocomposite film and various gas samples is considered. Complex permittivity for both stoichiometric and non-stoichiometric Au-WO3− nanocomposite films has been used for the simulation of the admittance loci plots, resonance curves and sensitivity curves by considering angular interrogation at a fixed wavelength of 632.8 nm.

  2. Gas sensing properties of Al-doped ZnO for UV-activated CO detection

    Science.gov (United States)

    Dhahri, R.; Hjiri, M.; El Mir, L.; Bonavita, A.; Iannazzo, D.; Latino, M.; Donato, N.; Leonardi, S. G.; Neri, G.

    2016-04-01

    Al-doped ZnO (AZO) samples were prepared using a modified sol-gel route and charaterized by means of trasmission electron microscopy, x-ray diffraction and photoluminescence analysis. Resistive planar devices based on thick films of AZO deposited on interdigitated alumina substrates were fabricated and investigated as UV light activated CO sensors. CO sensing tests were performed in both dark and illumination condition by exposing the samples to UV radiation (λ  =  400 nm).Under UV light, Al-doped ZnO gas sensors operated at lower temperature than in dark. Furthermore, by photoactivation we also promoted CO sensitivity and made signal recovery of AZO sensors faster. Results demonstrate that Al-doped ZnO might be a promising sensing material for the detection of CO under UV illumination.

  3. Finite size effect on hydrogen gas sensing performance in single Pd nanowires

    Science.gov (United States)

    Jeon, Kye Jin; Jeun, Minhong; Lee, Eunsongyi; Lee, Jun Min; Lee, Kyoung-Il; von Allmen, Paul; Lee, Wooyoung

    2008-12-01

    We present the hydrogen sensing performance of individual Pd nanowires grown by electrodeposition into nanochannels of anodized aluminum oxide (AAO) templates investigated as a function of the nanowire diameter. Four-terminal devices based on individual Pd nanowires were found to successfully detect hydrogen gas (H2). Our experimental results show that the H2 sensing sensitivity increases and the response time decreases with decreasing diameter of Pd nanowires with d = 400, 200, 80 and 20 nm, due to the high surface-to-volume ratio and short diffusion paths, respectively. This is in qualitatively good agreement with simulated results obtained from a theoretical model based on a combination of the rate equation and diffusion equation.

  4. Finite size effect on hydrogen gas sensing performance in single Pd nanowires.

    Science.gov (United States)

    Jeon, Kye Jin; Jeun, Minhong; Lee, Eunsongyi; Lee, Jun Min; Lee, Kyoung-Il; von Allmen, Paul; Lee, Wooyoung

    2008-12-10

    We present the hydrogen sensing performance of individual Pd nanowires grown by electrodeposition into nanochannels of anodized aluminum oxide (AAO) templates investigated as a function of the nanowire diameter. Four-terminal devices based on individual Pd nanowires were found to successfully detect hydrogen gas (H(2)). Our experimental results show that the H(2) sensing sensitivity increases and the response time decreases with decreasing diameter of Pd nanowires with d = 400, 200, 80 and 20 nm, due to the high surface-to-volume ratio and short diffusion paths, respectively. This is in qualitatively good agreement with simulated results obtained from a theoretical model based on a combination of the rate equation and diffusion equation.

  5. Numerical Analysis of Silicon Micromachined Gas Pendulum Tilt Sense Organ Temperature Field

    Institute of Scientific and Technical Information of China (English)

    Linhua Piao; Bin Zhang; Yaojie Lv; Fuxue Zhang

    2006-01-01

    An analysis of the sensitive mechanism of silicon micromachined gas pendulum tilt sense organ is made. Adopting the method of FEA (finite element analysis), the temperature field at two points heat source, when the two-dimensional enclosure was inclined, was obtained by application of the program ANSYS-FLOTRAN CFD and a series of procedures, such as modeling, meshing, loading and equation solving. The numerical results show that in the level state, the temperatures at two points heat source are two points in the same isotherm; however, the temperatures are not the same when the enclosure is inclined. The difference of the temperatures will increase with the augment of the tilt angle, and contrarily it will decrease. That is the characteristic used to sense the transformation of obliquity.

  6. State of the art stationary and mobile infrastructure for the dynamic generation and dilution of traceable reference gas mixtures of Ammonia at ambient air amount fractions

    Science.gov (United States)

    Leuenberger, Daiana; Pascale, Céline; Guillevic, Myriam; Ackermann, Andreas; Niederhauser, Bernhard

    2017-04-01

    Ammonia (NH3) in the atmosphere is the major precursor for neutralising atmospheric acids and is thus affecting not only the long-range transport of sulphur dioxide and nitrogen oxides but also stabilises secondary particulate matter. These aerosols have negative impacts on air quality and human health. Moreover, they negatively affect terrestrial ecosystems after deposition. NH3 has been included in the air quality monitoring networks and emission reduction directives of European nations. Atmospheric concentrations are in the order of 0.5-500 nmol/mol. However, the lowest substance amount fraction of available certified reference material (CRM) is 10 μmol/mol. This due to the fact that adsorption on the walls of aluminium cylinders and desorption as pressure in the cylinder decreases cause substantial instabilities in the amount fractions of the gas mixtures. Moreover, analytical techniques to be calibrated are very diverse and cause challenges for the production and application of CRM. The Federal Institute of Metrology METAS has developed, partially in the framework of EMRP JRP ENV55 MetNH3, an infrastructure to meet with the different requirements in order to generate SI-traceable NH3 reference gas mixtures dynamically in the amount fraction range 0.5-500 nmol/mol and with uncertainties UNH3 filling. The mobile system as well as these cylinders can be applied for calibrations in other laboratories and in the field. In addition, an SI traceable system based on a cascade of critical orifices has been established to dilute NH3 mixtures in the order of μmol/mol stored in cylinders for the participation in the international key-comparison CCQM K117. It is planned to establish this system to calibrate and re-sample gas cylinders due to its very economical gas use. Here we present insights into the development of said infrastructure and results of the first performance tests. Moreover, we include results of the study on adsorption/desorption effects in dry as well

  7. Effect of Unsaturated Sn Atoms on Gas-Sensing Property in Hydrogenated SnO2 Nanocrystals and Sensing Mechanism.

    Science.gov (United States)

    Yuan, Y; Wang, Y; Wang, M; Liu, J; Pei, C; Liu, B; Zhao, H; Liu, S; Yang, H

    2017-04-27

    Sensing reaction mechanism is crucial for enhancing the sensing performance of semiconductor-based sensing materials. Here we show a new strategy to enhancing sensing performance of SnO2 nanocrystals by increasing the density of unsaturated Sn atoms with dangling bonds at the SnO2 surface through hydrogenation. A concept of the surface unsaturated Sn atoms serving as active sites for the sensing reaction is proposed, and the sensing mechanism is described in detail at atomic and molecule level for the first time. Sensing properties of other metal oxide sensors and catalytic activity of other catalysts may be improved by using the hydrogenation strategy. The concept of the surface unsaturated metal atoms serving as active sites may be very useful for understanding the sensing and catalytic reaction mechanisms and designing advanced sensing sensors, catalysts and photoelectronic devices.

  8. Monitoring Hydrogen Sulfide Using a Quantum Cascade Laser Based Trace Gas Sensing System

    Institute of Scientific and Technical Information of China (English)

    WANG Ling-Fang; SHARPLES Thomas-Roben

    2011-01-01

    @@ We present the detection of hydrogen sulfide (HS) in a quantum cascade laser (QCL) based gas sensing system employing direct laser absorption spectroscopy.The sensitivity is obtained to be 3.61 × 10 cm Hz and the HS broadening coefficient in N is analyzed by fitting to the plot of the Lorentzian half width at the half maximum as a function of N pressure is 0.1124±0.0031 cm.atm.A simulation based on data from the HITRAN database shows broad agreement with the experimentally obtained spectrum.

  9. High-performance gas sensing achieved by mesoporous tungsten oxide mesocrystals with increased oxygen vacancies

    KAUST Repository

    Wang, Dong

    2013-01-01

    The inner structure of W18O49 mesocrystals was observed by electron microscopy with the help of ultramicrotomy and focused ion beam techniques. The results showed that these mesocrystals contain irregular mesopores formed through partial fusion of self-assembled nanowires, and consequently have long-range structural ordering in one dimension and short-range ordering in the other two dimensions. The W18O 49 mesocrystals exhibit superior performance in gas sensing applications, which is considered to be associated with the presence of more oxygen vacancy sites in the unique mesoporous structure. © 2013 The Royal Society of Chemistry.

  10. Influence of Fabricating Process on Gas Sensing Properties of ZnO Nanofiber-Based Sensors

    Institute of Scientific and Technical Information of China (English)

    XU Lei; WANG Rui; LIU Yong; DONG Liang

    2011-01-01

    @@ ZnO nanofibers are synthesized by an electrospinning method and characterized by x-ray diffraction(XRD)and scanning electron microscopy(SEM).Two types of gas sensors are fabricated by loading these nanofibers as the sensing materials and their performances are investigated in detail.Compared with the sensors based on traditional ceramic tubes with Au electrodes(traditional sensors), the sensors fabricated by spinning ZnO nanofibers on ceramic planes with Ag-Pd electrodes(plane sensors)exhibit much higher sensing properties.The sensitivity for the plane sensors is about 30 to 100ppm ethanol at 300℃, while the value is only 13 for the traditional sensors.The response and recovery times are about 2 and 3s for the plane sensors and are 3 and 6s for the traditional sensors, respectively.Lower minimum-detection-limit is also found for the plane sensors.These improvements are explained by considering the morphological damage in the fabricating process for traditional sensors.The results suggest that the plane sensors are more suitable to sensing investigation for higher veracity.%ZnO nanofibers are synthesized by an electrospinning method and characterized by x-ray diffraction (XRD)and scanning electron microscopy (SEM). Two types of gas sensors are fabricated by loading these nanofibers as the sensing materials and their performances are investigated in detail. Compared with the sensors based on traditional ceramic tubes with Au electrodes (traditional sensors), the sensors fabricated by spinning ZnO nanofibers on ceramic planes with Ag-Pd electrodes (plane sensors) exhibit much higher sensing properties. The sensitivity for the plane sensors is about 30 to l00ppm ethanol at 300℃, while the value is only 13 for the traditional sensors. The response and recovery times are about 2 and 3s for the plane sensors and are 3 and 6s for the traditional sensors, respectively. Lower minimum-detection-limit is also found for the plane sensors. These improvements are explained

  11. Development and Application of Gas Sensing Technologies to Enable Boiler Balancing

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Prabir

    2008-12-31

    Identifying gas species and their quantification is important for optimization of many industrial applications involving high temperatures, including combustion processes. CISM (Center for Industrial Sensors and Measurements) at the Ohio State University has developed CO, O{sub 2}, NO{sub x}, and CO{sub 2} sensors based on TiO{sub 2} semiconducting oxides, zirconia and lithium phosphate based electrochemical sensors and sensor arrays for high-temperature emission control. The underlying theme in our sensor development has been the use of materials science and chemistry to promote high-temperature performance with selectivity. A review article presenting key results of our studies on CO, NO{sub x}, CO{sub 2} and O{sub 2} sensors is described in: Akbar, Sheikh A.; Dutta, Prabir K. Development and Application of Gas Sensing Technologies for Combustion Processes, PowerPlant Chemistry, 9(1) 2006, 28-33.

  12. Acetone gas sensing mechanism on zinc oxide surfaces: A first principles calculation

    Science.gov (United States)

    Sadeghian Lemraski, M.; Nadimi, E.

    2017-03-01

    Semiconducting metal oxide gas sensors have attracted growing interest as a result of their outstanding performance in the bio and industrial applications. Nevertheless, the sensing mechanism is yet not totally understood. In this study, we extensively investigate the adsorption mechanism of acetone molecule on ZnO-based thin film sensors by performing ab initio density functional theory calculations and employing quantum molecular dynamic simulations. Since the sensitivity of a metal oxide sensor is exceedingly depends on molecular oxygen exposure and operating temperature, we explore the competitive adsorption of acetone and oxygen molecule on the most stable orientation of ZnO surface (10 1 ̅ 0) at different temperatures. Results indicate that at elevated temperatures acetone gains required thermal energy to remove preadsorbed oxygen molecule from the surface in a competitive process. We will show that this competition is responsible for the resistive switching behavior in the ZnO-based gas sensors.

  13. Graphene enhanced evanescent field in microfiber multimode interferometer for highly sensitive gas sensing.

    Science.gov (United States)

    Yao, B C; Wu, Y; Zhang, A Q; Rao, Y J; Wang, Z G; Cheng, Y; Gong, Y; Zhang, W L; Chen, Y F; Chiang, K S

    2014-11-17

    Graphene based new physics phenomena are leading to a variety of stimulating graphene-based photonic devices. In this study, the enhancement of surface evanescent field by graphene cylindrical cladding is observed, for the first time, by using a graphene-coated microfiber multi-mode interferometer (GMMI). It is found theoretically and experimentally that the light transmitting in the fiber core is efficiently dragged by the graphene, hence significantly enhancing the evanescent fields, and subsequently improving the sensitivity of the hybrid waveguide. The experimental results for gas sensing verified the theoretical prediction, and ultra-high sensitivities of ~0.1 ppm for NH(3) gas detection and ~0.2 ppm for H(2)O vapor detection are achieved, which could be used for trace analysis. The enhancement of surface evanescent field induced by graphene may pave a new way for developing novel graphene-based all-fiber devices with compactness, low cost, and temperature immunity.

  14. Experimental research of optical fiber hydrogen gas sensing system based on palladium-silver alloy

    Science.gov (United States)

    Cui, Lu-jun; Zhou, Gao-feng; Li, Zheng-feng; Cao, Yan-long

    2016-11-01

    A novel optical fiber hydrogen sensing system based on palladium (Pd) and sliver (Ag) is proposed. By direct current (DC) magnetron process, Pd/Ag alloy ultra-thin films were deposited on the substrate to eliminate the hydrogen embrittlement of sensor based on pure Pd. Several samples with different thin film thicknesses were fabricated at different substrate temperatures and tested in the optical fiber hydrogen sensor setup. We do a series of experiments for obtaining optimum sputtering parameters, such as optimum sputtering temperature and thickness of Pd/Ag alloy film. The humidity effect and reliability experiment for the optical fiber hydrogen gas sensor are reported in detail. The testing results demonstrate the Pd/Ag alloy is a promising material for optical fiber hydrogen gas sensor.

  15. Fabrication of Porous TiO2 Hollow Spheres and Their Application in Gas Sensing

    Directory of Open Access Journals (Sweden)

    Hu Peng

    2010-01-01

    Full Text Available Abstract In this work, porous TiO2 hollow spheres with an average diameter of 100 nm and shell thickness of 20 nm were synthesized by a facile hydrothermal method with NH4HCO3 as the structure-directing agent, and the formation mechanism for this porous hollow structure was proved to be the Ostwald ripening process by tracking the morphology of the products at different reaction stages. The product was characterized by SEM, TEM, XRD and BET analyses, and the results show that the as-synthesized products are anatase phase with a high surface area up to 132.5 m2/g. Gas-sensing investigation reveals that the product possesses sensitive response to methanal gas at 200°C due to its high surface area.

  16. Nitrogen-monoxide gas-sensing properties of transparent p-type copper-oxide nanorod arrays

    Energy Technology Data Exchange (ETDEWEB)

    Park, Soojeong; Kim, Hyojin; Kim, Dojin [Chungnam National University, Daejeon (Korea, Republic of)

    2015-01-15

    We report the nitrogen-monoxide (NO) gas-sensing properties of transparent p-type copper-oxide (CuO) nanorod arrays synthesized by using the hydrothermal method with a CuO nanoparticle seed layer deposited on a glass substrate via sputtering process. We synthesized polycrystalline CuO nanorods measuring 200 to 300 nm in length and 20 to 30 nm in diameter for three controlled molarity ratios of 1:1, 1:2 and 1:4 between copper nitrate trihydrate [Cu(NO{sub 2}){sub 2}·3H{sub 2}O] and hexamethylenetetramine (C{sub 6}H{sub 12}N{sub 4}). The crystal structures and morphologies of the synthesized CuO nanorod arrays were examined using grazing incidence X-ray diffraction and scanning electron microscopy. The gas-sensing measurements for NO gas in dry air indicated that the CuO nanorodarray-based gas sensors synthesized under hydrothermal condition at a molarity ratio of 1:2 showed the best gas sensing response to NO gas. These CuO nanorod-array gas sensors exhibited a highly sensitive response to NO gas, with a maximum sensitivity of about 650% for 10 ppm NO in dry air at an operating temperature of 100 .deg. C. These transparent p-type CuO nanorod-array gas sensors have shown a reversible and reliable response to NO gas over a range of operating temperatures. These results indicate certain potential use of p-type oxide semiconductor CuO nanorods as sensing materials for several types of gas sensors, including p - n junction gas sensors.

  17. Controllable synthesis of Co{sub 3}O{sub 4}/polyethyleneimine-carbon nanotubes nanocomposites for CO and NH{sub 3} gas sensing at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yufei [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Kan, Kan [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Institute of Advanced Technology, Heilongjiang Academy of Sciences, Harbin 150000 (China); Song, Wanzhen; Zhang, Guo; Dang, Lifang [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Xie, Yu [Department of Materials Chemistry, Nanchang Hangkong University, Nanchang 330063 (China); Shen, Peikang [Department of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Li, Li, E-mail: llwjjhlju@sina.cn [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Key Laboratory of Chemical Engineering Process & Technology for High-efficiency Conversion, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Shi, Keying, E-mail: shikeying2008@163.com [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China)

    2015-08-05

    Graphical abstract: Co{sub 3}O{sub 4}/polyethyleneimine-carbon nanotubes composites (CoPCNTs) have been successfully controllable synthesized via hydrothermal method at different temperature. The CoPCNTs sensors exhibited the highest response to CO and NH{sub 3} gases with response time of 4 s and 4.3 s, low detection limit of 5 ppm and 1 ppm at room temperature, respectively. The enhanced gas sensing could be ascribed to the synergistic effect between the tiny size of Co{sub 3}O{sub 4} and good conductivity of carbon nanotubes functionalized by polyethyleneimine. - Highlights: • The CNTs functionalized by polyethyleneimine provided a new functional structural. • The novel 1D structure could capture and migrate electrons quickly. • The Co{sub 3}O{sub 4} nanoparticles liked a snake winding around CNTs. • The gas sensor could work at room temperatures, which suit to practical application. - Abstract: A novel 1D Co{sub 3}O{sub 4}/polyethyleneimine-carbon nanotubes composites (CoPCNTs) have been successfully synthesized via hydrothermal method at different temperature. The CNTs functionalized by polyethyleneimine (PCNTs) provided a new material with new structural and functional properties. The PCNTs was used as loading guider and electron transfer path. The Co{sub 3}O{sub 4} nanoparticles (NPs) loaded on the PCNTs surface liked a snake winding around CNTs, and the size was about 5–10 nm. The gas sensing characteristics of the CoPCNTs sensors to carbon monoxide (CO) and ammonia (NH{sub 3}) were evaluated with different gas concentration. The CoPCNTs sensors grown at 160 °C exhibited the highest response to CO and NH{sub 3} gases with response time of 4 s and 4.3 s at room temperature (RT), respectively. Hence, the approach developed in this work would be important for the low-cost and large-scale production of the CoPCNTs materials with highly promising applications in gas sensors.

  18. Plasmonic nanoantenna array with single-chip integrated metal-organic framework for infrared absorption gas sensing (Conference Presentation)

    Science.gov (United States)

    Chong, Xinyuan; Kim, Ki-Joong; Li, Erwen; Zhang, Yujing; Ohodnicki, Paul R.; Chang, Chih-Hung; Wang, Alan X.

    2017-03-01

    Surface-enhanced infrared absorption (SEIRA) is a spectroscopic technique used to identify molecular fingerprints by resonant detection of infrared vibrational modes through coupling with the plasmonic modes of metallic nanostructures. Many reported works have demonstrated its capability to enhance the infrared absorption of solid or liquid samples. However, this technique has not been successfully applied to gas sensing yet due to the short light-matter interaction length and intrinsically weak absorption of gas compared to solid or liquid materials. Usually, IR gas sensing is conducted in a gas cell with a long absorption path. In the paper, we propose an integrated photonic device to expand the application of SEIRA to gas sensing by combining metal-organic framework (MOF) ZIF-8 (zeolitic imidazole framework) with plasmonic nanoantenna array. The device consists of an Au nanopatch array on sapphire substrate and is covered by a thin layer of MOF material. The MOF thin film, which is a new class of highly nanoporous material, serves as a gas absorber to selectively adsorb and concentrate CO2 from ambient environment into the thin layer, which has a high spatial overlap with the high intensity optical field of the plasmonic nanopatch antenna array. Namely, we can effectively increase the gas molecule concentration at the hot-spots for the SEIRA device. The experimentally demonstrated peak IR enhancement factor of the device for carbon dioxide sensing is over 1,100 times.

  19. Fe-Doped TiO2 Thin Films for CO Gas Sensing

    Science.gov (United States)

    Kumar, Mukesh; Kumar, Dinesh; Gupta, Anil Kumar

    2015-01-01

    Fe-doped TiO2 thin films were prepared by the sol-gel technique on silicon substrate. The thin films were evaluated for detection of carbon monoxide (CO) gas at room temperature. The TiO2 films were characterized by x-ray diffraction (XRD) analysis, field-emission scanning electron microscopy, and ultraviolet-visible (UV) spectroscopy. The characterization revealed that, as the doping concentration was increased, the grain size decreased. XRD patterns revealed the phase transition from rutile to anatase with addition of different percentages (weight/volume) of Fe. The bandgap determined from UV spectroscopy was found to decrease with increasing Fe doping concentration. Fe doping was observed to have a significant effect on the resistivity of the doped TiO2 thin films. The gas sensing behavior of the films was studied by exposure to different concentrations of CO gas with measurement of the electrical resistance. It was observed that Fe-doped (7% weight/volume) TiO2 exhibited high sensitivity and good response/recovery on exposure to CO gas in the concentration range from 100 ppm to 900 ppm in Ar.

  20. Examining the Gas Sensing Properties of the Nanocrystalline Sm2O3-WO3

    Institute of Scientific and Technical Information of China (English)

    邓粲达; 林冠男; 林鸿明; 杨宗烨

    2004-01-01

    In this study, nanocrystalline (NC) WO3 and Sm2O3-WO3 gas sensors have been synthesized and deposited on Al2O3 substrate by gas condensation method, then sintering to 600℃. SEM is used to observe the morphology of the surface. TEM is used to measure the particle size. The resistance of sensor is measured in different temperatures and gas concentration to evaluate the sensing properties of NC WO3 and NC Sm2O3-WO3 sensor. The results indicate that WO3 is a usability gas sensor material. After Sm2O3 is doped in WO3, it does not obviously influence CO detection; it owns better sensitivity and stability. To UV irradiation on WO3, the sensitivity of WO3 is enhanced and it maintains WO3 recovery properties in NO2 detecting. UV irradiation on Sm2O3 doped WO3 does not show enhanced well properties as UV illuminate on WO3.

  1. Carbon monoxide gas sensing using zinc oxide film deposited by spray pyrolysis

    Science.gov (United States)

    Leano, J. M. G.; Villapando, J. M. L. A.; Balaaldia, A. E.; Gianan, G.; Manalo, F. K. B.; Florido, E. A.

    2017-05-01

    This study was aimed to determine the carbon monoxide (CO) gas sensing ability of zinc oxide (ZnO) film fabricated by spray pyrolysis on glass substrate heated at 3000C using 0.2 M zinc acetate precursor solution. The temperature of the precursor solution was maintained at room temperature. Carbon monoxide gas was synthesized by mixing the required amount of formic acid and excess sulfuric acid in the ratio of 1:6 to produce CO gas concentrations of 100, 200, 300, 400, and 500 parts per million (ppm) v/v. There were five trials for each concentration. The films produced exhibited good sensor characteristics such as high linearity in current voltage relationship and voltage response versus concentration. Electrical characterization using the four-point probe showed a linear relationship between current and voltage with resistivity of 0.49 ohm-cm and R2 value of 0.994 The zinc oxide film exhibited a sensitivity of 0.19 Volt per 100 ppm of CO gas and linearity R2 value of 0.993.

  2. A UAV-based gas sensing system for detecting fugitive methane emissions

    Science.gov (United States)

    Hugenholtz, C.; Barchyn, T.; Myshak, S.; Bauer, J.

    2016-12-01

    Methane is one of the most prevalent greenhouse gases emitted by human activities and is a major component of government-led initiatives to reduce GHG emissions in Canada, the USA, and elsewhere. In light of growing demand for measurements and verification of atmospheric methane concentration across the oil and gas supply chain, an autonomous airborne gas sensing system was developed that combines a small UAV and a lightweight gas monitor. This paper outlines the technology, analytics, and presents data from a case study to demonstrate the proof of concept. The UAV is a fixed-wing (2.2 m wingspan), battery-operated platform, with a flight endurance of 80-120 minutes. The gas sensor onboard the UAV is a tunable diode laser absorption spectrometer that uses an integrated transmitter/receiver unit and a remote, passive retro-reflector. The transmitter is attached to one of the winglets, while the other is coated with reflective material. The total weight of the UAV and gas sensor is 4.3 kg. During flight, the system operates autonomously, acquiring averages of raw measurements at 1 Hz, with a recorded resolution of 0.0455 ppm. The onboard measurement and control unit (MCU) for the gas sensor is integrated with the UAV autopilot in order to provide time-stamped and geotagged concentration measurements, and to provide real-time flight adjustments when concentration exceeds a pre-determined threshold. The data are retrieved from the MCU when the mission is complete. In order to demonstrate the proof of concept, we present results from a case study and outline opportunities for translating the measurements into decision making.

  3. Determination of Ammonia-nitrogen in the Dyeing Wastewater by the Gas-phase Molecular Absorption Spectrometry%气相分子吸收光谱法测定印染废水中的氨氮

    Institute of Scientific and Technical Information of China (English)

    徐运; 肖国起

    2011-01-01

    本文用气相分子吸收光谱法测定印染废水中的氨氮。气相分子吸收光谱法应用国内的气相分子吸收光谱仪测定印染废水中氨氮,与纳氏试剂法相比较,该方法快捷简单、受干扰小、分析精度高。%This paper introduced the gas-phase molecular absorption spectrometry for the ammonia-nitrogen in the dyeing wastewater.The gas-phase molecular absorption spectrometry applied the as-phase molecular absorption spectrophotometer device to analyze the ammonia-nitrogen in the dyeing wastewater.Compared with the Nesster's reagent colorimetric method,this method was fast,simple,less-disturbance and highly perceptive.

  4. Effects of Feeding Encapsulated Nitrate to Beef Cattle on Ammonia and Greenhouse Gas Emissions from Their Manure in a Short-Term Manure Storage System.

    Science.gov (United States)

    Lee, Chanhee; Araujo, Rafael C; Koenig, Karen M; Hile, Michael L; Fabian-Wheeler, Eileen E; Beauchemin, Karen A

    2016-11-01

    A study was conducted to investigate effects of feeding encapsulated nitrate (EN) to beef cattle on ammonia (NH) and greenhouse gas emissions from their manure. Eight beef heifers were randomly assigned to diets containing 0 (control), 1, 2, or 3% EN (55% forage dry matter; EN replaced encapsulated urea in the control diet and therefore all diets were iso-nitrogenous) in a replicated 4 × 4 Latin square design. Urine and feces collected from individual animals were reconstituted into manure and incubated over 156 h using a steady-state flux chamber system to monitor NH, methane (CH), carbon dioxide (CO), and nitrous oxide (NO) emissions. Urinary, fecal, and manure nitrate (NO)-N concentration linearly increased ( feeding EN, and urinary urea concentration tended to be lower ( = 0.078) for EN versus Control. The hourly emissions of NH, CO, and NO (mg head h) were not affected, although NH emission rates tended to be lower ( = 0.070) for EN compared with Control at 0 to 12 h. Cumulative NH, CO, and NO emissions over 156 h were not affected, but CH emissions were less (4.5 vs. 7.4 g head; = 0.027) for EN compared with Control. In conclusion, although NH emissions were initially lower for EN manures, total NH emitted over 156 h was not affected. Dietary EN lowered CH emissions from manure, and, despite greater NO concentrations in EN manure, NO emissions were not affected in this short-term incubation.

  5. Kinetic studies on hydrolysis of urea in a semi-batch reactor at atmospheric pressure for safe use of ammonia in a power plant for flue gas conditioning

    Energy Technology Data Exchange (ETDEWEB)

    Mahalik, K. [Department of Chemical Engineering, Indian Institute of Technology (IIT), Kharagpur, P.O. Kharagpur Technology, West Bengal 721302 (India); Department of Chemical Engineering, Gandhi Institute of Engineering and Technology, Gunupur, Orissa (India); Sahu, J.N., E-mail: jnsahu@um.edu.my [Department of Chemical Engineering, Indian Institute of Technology (IIT), Kharagpur, P.O. Kharagpur Technology, West Bengal 721302 (India); Department of Chemical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Patwardhan, Anand V. [Department of Chemical Engineering, Institute of Chemical Technology (ICT), Mumbai 400019 (India); Meikap, B.C. [Department of Chemical Engineering, Indian Institute of Technology (IIT), Kharagpur, P.O. Kharagpur Technology, West Bengal 721302 (India); School of Chemical Engineering, University of KwaZulu-Natal, Faculty of Engineering, Howard College Campus, King George V. Avenue, Durban 4041 (South Africa)

    2010-03-15

    With growing industrialization in power sector, air is being polluted with a host of substances-most conspicuously with suspended particulate matter emanating from coal-fired thermal power plants. Flue gas conditioning, especially in such power plants, requires in situ generation of ammonia. In the present paper, experiments for kinetic study of hydrolysis of urea have been conducted using a borosil glass reactor, first without stirring followed by with stirring. The study reveals that conversion increases exponentially with an increase in temperature and feed concentration. Furthermore, the effect of stirring speed, temperature and concentration on conversion has been studied. Using collision theory, temperature dependency of forward rate constant has been developed from which activation energy of the reaction and the frequency factors have been calculated. It has been observed that the forward rate constant increases with an increase in temperature. The activation energy and frequency factor with stirring has been found to be 59.85 kJ/mol and 3.9 x 10{sup 6} min{sup -1} respectively with correlation co-efficient and standard deviation being 0.98% and {+-}0.1% in that order.

  6. Back propagation neural network model for predicting the performance of immobilized cell biofilters handling gas-phase hydrogen sulphide and ammonia.

    Science.gov (United States)

    Rene, Eldon R; López, M Estefanía; Kim, Jung Hoon; Park, Hung Suck

    2013-01-01

    Lab scale studies were conducted to evaluate the performance of two simultaneously operated immobilized cell biofilters (ICBs) for removing hydrogen sulphide (H2S) and ammonia (NH3) from gas phase. The removal efficiencies (REs) of the biofilter treating H2S varied from 50 to 100% at inlet loading rates (ILRs) varying up to 13 g H2S/m(3) ·h, while the NH3 biofilter showed REs ranging from 60 to 100% at ILRs varying between 0.5 and 5.5 g NH3/m(3) ·h. An application of the back propagation neural network (BPNN) to predict the performance parameter, namely, RE (%) using this experimental data is presented in this paper. The input parameters to the network were unit flow (per min) and inlet concentrations (ppmv), respectively. The accuracy of BPNN-based model predictions were evaluated by providing the trained network topology with a test dataset and also by calculating the regression coefficient (R (2)) values. The results from this predictive modeling work showed that BPNNs were able to predict the RE of both the ICBs efficiently.

  7. Back Propagation Neural Network Model for Predicting the Performance of Immobilized Cell Biofilters Handling Gas-Phase Hydrogen Sulphide and Ammonia

    Directory of Open Access Journals (Sweden)

    Eldon R. Rene

    2013-01-01

    Full Text Available Lab scale studies were conducted to evaluate the performance of two simultaneously operated immobilized cell biofilters (ICBs for removing hydrogen sulphide (H2S and ammonia (NH3 from gas phase. The removal efficiencies (REs of the biofilter treating H2S varied from 50 to 100% at inlet loading rates (ILRs varying up to 13 g H2S/m3·h, while the NH3 biofilter showed REs ranging from 60 to 100% at ILRs varying between 0.5 and 5.5 g NH3/m3·h. An application of the back propagation neural network (BPNN to predict the performance parameter, namely, RE (% using this experimental data is presented in this paper. The input parameters to the network were unit flow (per min and inlet concentrations (ppmv, respectively. The accuracy of BPNN-based model predictions were evaluated by providing the trained network topology with a test dataset and also by calculating the regression coefficient (R2 values. The results from this predictive modeling work showed that BPNNs were able to predict the RE of both the ICBs efficiently.

  8. Graphene-based LbL deposited films: further study of electrical and gas sensing properties

    Directory of Open Access Journals (Sweden)

    Nabok A.

    2017-01-01

    Full Text Available Graphene-surfactant composite materials obtained by the ultrasonic exfoliation of graphite powder in the presence of ionic surfactants (either CTAB or SDS were utilised to construct thin films using layer-by-layer (LbL electrostatic deposition technique. A series of graphene-based thin films were made by alternating layers of either graphene-SDS with polycations (PEI or PAH or graphene-CTAB with polyanions (PSS. Also, graphene-phthalocyanine composite films were produced by alternating layers of graphene-CTAB with tetrasulfonated nickel phthalocyanine. Graphene-surfactant LbL films exhibited good electric conductivity (about 0.1 S/cm of semiconductor type with a band gap of about 20 meV. Judging from UV-vis spectra measurements, graphene-phthalocyanine LbL films appeared to form joint π-electron system. Gas sensing testing of such composite films combining high conductivity of graphene with the gas sensing abilities of phthalocyanines showed substantial changes (up to 10% in electrical conductivity upon exposure to electro-active gases such as HCl and NH3.

  9. Structural, electrical and gas-sensing properties of In2O3 : Ag composite nanoparticle layers

    Indian Academy of Sciences (India)

    B R Mehta; V N Singh

    2005-11-01

    The central objective of this study is to investigate (i) size-dependent properties of In2O3 nanoparticles and (ii) the role of metal additives in enhancing the gas sensing response. For this purpose, In2O3 : Ag composite nanoparticle layers having well-defined individual nanoparticle size and composition have been grown by a two step synthesis method. Thermogravimetric analysis, X-ray diffraction and transmission electron microscopy have been used to study the effect of post-synthesis heat treatment on the size and structure of the nanoparticles. A first-time unambiguous observation of size-dependent lowering of transformation temperature has been explained in terms of lower cohesive energy of surface atoms and increase in surface-to-volume ratio with decrease in nanoparticle size. The gas sensing studies of In2O3 as well as the In2O3 : Ag composite nanoparticle layers have been studied as a function of size and composition. In2O3 : Ag composite nanoparticle layers with 15% silver show a sensitivity of 436 and response time of 6 s for 1000 ppm of ethanol in air. Ag additives form a p-type Ag2O, which interact with n-type In2O3 to produce an electron-deficient space-charge layer. In the presence of ethanol, interfacial Ag2O reduces to Ag, creating an accumulation layer in In2O3 resulting in increased sensitivity.

  10. UV-assisted room temperature gas sensing of GaN-core/ZnO-shell nanowires

    Science.gov (United States)

    Park, Sunghoon; Ko, Hyunsung; Kim, Soohyun; Lee, Chongmu

    2014-11-01

    GaN is highly sensitive to low concentrations of H2 in ambient air and is almost insensitive to most other common gases. However, enhancing the sensing performance and the detection limit of GaN is a challenge. This study examined the H2-gas-sensing properties of GaN nanowires encapsulated with ZnO. GaN-core/ZnO-shell nanowires were fabricated by using a two-step process comprising the thermal evaporation of GaN powders and the atomic layer deposition of ZnO. The core-shell nanowires ranged from 80 to 120 nm in diameter and from a few tens to a few hundreds of micrometers in length, with a mean shell layer thickness of ~8 nm. Multiple-networked pristine GaN nanowire and ZnO-encapsulated GaN (or GaN-core/ZnO-shell) nanowire sensors showed responses of 120-147% and 179-389%, respectively, to 500-2,500 ppm of H2 at room temperature under UV (254 nm) illumination. The underlying mechanism of the enhanced response of the GaN nanowire to H2 gas when using ZnO encapsulation and UV irradiation is discussed.

  11. Improving Gas Sensing Properties of Tin Oxide Nanowires Palladium-Coated Using a Low Cost Technique

    Directory of Open Access Journals (Sweden)

    M. Barzegar

    2012-12-01

    Full Text Available Thin films of SnO2 nanowires were successfully prepared by using chemical vapor deposition (CVD process on quartz substrates. Afterwards, a thin  layer of palladium (Pd as a catalyst was coated on top of nanowires. For the deposition of Pd, a simple and low cost technique of spray pyrolysis was employed, which caused an intensive enhancement on the sensing response of fabricated sensors. Prepared sensor devices were exposed to liquid petroleum gas (LPG and vapor of ethanol (C2H5OH. Results indicate that SnO2 nanowires sensors coated with Pd as a catalyst show decreasing in response time (~40s to 1000ppm of LPG at a relatively low operating temperature (200o C. SnO2 /Pd nanowire devices show gas sensing response time and recovery time as short as 50s and 10s respectively with a high sensitivity value of ~120 for C2H5OH, that is remarkable in comparison with other reports.

  12. Fast optical NO sub 2 gas sensing of porphyrin Langmuir-Blodgett films

    CERN Document Server

    Dooling, C M

    2002-01-01

    A porphyrin sensor for the detection of NO sub 2 gas in the 0.1-5.0 ppm range has been developed. The sensing characteristics of 5,10,15,20-tetrakis(3,4,-bis[-ethylhexyloxy]phenyl)-21H,23H-porphine (EHO) Langmuir-Blodgett (LB) films are shown to be dependent on a range of parameters including surface pressure, film thickness and deposition speed. This research has led to exceptionally fast response times with the best t sub 5 sub 0 values of approx 15s achieved with relatively large absorbance changes of typically 60%. The kinetics of the sensing response have been simulated using the Elovichian model and shown to exhibit Langmuirian and Arrhenius behaviour. Ultra-fast LB deposition (500-1000 mm min sup - sup 1) has been developed as a means of both decreasing sample production time and increasing the surface area - volume ratio for enhanced gas response. This technique maintains orientational symmetry and high transfer ratio, yet displays a highly disordered porous structure. The 'bed of nails' texture is pr...

  13. Nickel oxide nanowires: vapor liquid solid synthesis and integration into a gas sensing device.

    Science.gov (United States)

    Kaur, N; Comini, E; Zappa, D; Poli, N; Sberveglieri, G

    2016-05-20

    In the field of advanced sensor technology, metal oxide nanostructures are promising materials due to their high charge carrier mobility, easy fabrication and excellent stability. Among all the metal oxide semiconductors, nickel oxide (NiO) is a p-type semiconductor with a wide band gap and excellent optical, electrical and magnetic properties, which has not been much investigated. Herein, we report the growth of NiO nanowires by using the vapor liquid solid (VLS) technique for gas sensing applications. Platinum, palladium and gold have been used as a catalyst for the growth of NiO nanowires. The surface morphology of the nanowires was investigated through scanning electron microscopy to find out which catalyst and growth conditions are best for the growth of nanowires. GI-XRD and Raman spectroscopies were used to confirm the crystalline structure of the material. Different batches of sensors have been prepared, and their sensing performances towards different gas species such as carbon monoxide, ethanol, acetone and hydrogen have been explored. NiO nanowire sensors show interesting and promising performances towards hydrogen.

  14. Enhanced Gas Sensing Properties of Spin-coated Na-doped ZnO Nanostructured Films

    Science.gov (United States)

    Basyooni, Mohamed A.; Shaban, Mohamed; El Sayed, Adel M.

    2017-01-01

    In this report, the structures, morphologies, optical, electrical and gas sensing properties of ZnO and ZnO: Na spin-coated films are studied. X-ray diffraction (XRD) results reveal that the films are of a single phase wurtzite ZnO with a preferential orientation along (002) direction parallel to c-axis. Na doping reduces the crystalline quality of the films. The plane surface of ZnO film turned to be wrinkle net-work structure after doping. The reflectance and the optical band gap of the ZnO film decreased after Na doping. The wrinkle net-work nanostructured Na-doped film shows an unusually sensitivity, 81.9% @ 50 sccm, for CO2 gas at room temperature compared to 1.0% for the pure ZnO film. The signals to noise ratio (SNR) and detection limit of Na-doped ZnO sensor are 0.24 and 0.42 sccm, respectively. These enhanced sensing properties are ascribed to high surface-to-volume ratio, hoping effect, and the increase of O- vacancies density according to Kroger VinK effect. The response time increased from 179 to 240 s by the incorporation of Na atoms @50 sccm. This response time increased as the CO2 concentration increased. The recovery time is increased from 122 to 472 s by the incorporation of Na atoms @50 sccm. PMID:28145506

  15. A MEMS-based Benzene Gas Sensor with a Self-heating WO3 Sensing Layer

    Directory of Open Access Journals (Sweden)

    Lung-Ming Fu

    2009-04-01

    Full Text Available In the study, a MEMS-based benzene gas sensor is presented, consisting of a quartz substrate, a thin-film WO3 sensing layer, an integrated Pt micro-heater, and Pt interdigitated electrodes (IDEs. When benzene is present in the atmosphere, oxidation occurs on the heated WO3 sensing layer. This causes a change in the electrical conductivity of the WO3 film, and hence changes the resistance between the IDEs. The benzene concentration is then computed from the change in the measured resistance. A specific orientation of the WO3 layer is obtained by optimizing the sputtering process parameters. It is found that the sensitivity of the gas sensor is optimized at a working temperature of 300 °C. At the optimal working temperature, the experimental results show that the sensor has a high degree of sensitivity (1.0 KΩ ppm-1, a low detection limit (0.2 ppm and a rapid response time (35 s.

  16. Gas sensing properties of graphene–WO{sub 3} composites prepared by hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Xiangfeng, E-mail: xfchu99@ahut.edu.cn [School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan 243002 (China); Hu, Tao [School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan 243002 (China); Gao, Feng [Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Dong, Yongping; Sun, Wenqi; Bai, Linshan [School of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan 243002 (China)

    2015-03-15

    Graphical abstract: - Highlights: • The amount of graphene had an effect on the morphology of graphene–WO{sub 3} composites. • The optimum temperature of 0.1 wt% graphene–WO{sub 3} sensor to acetaldehyde was 100 °C. • 0.1 wt% graphene–WO{sub 3} sensor exhibited good selectivity to acetaldehyde at 100 °C. - Abstract: Graphene–WO{sub 3} composites mixed with different amounts of graphene (0, 0.1, 0.5, 1 and 3 wt%) were prepared by hydrothermal method at 180 °C for 24 h. The as-prepared graphite oxide, graphene and graphene–WO{sub 3} composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR) and Raman spectroscopy, respectively. The effect of the amount of graphene in the composites on the gas-sensing responses and the gas-sensing selectivity of the materials was investigated. The experimental results revealed that the sensor based on 0.1 wt% graphene–WO{sub 3} composite exhibited high response and good selectivity to acetaldehyde vapor at 100 °C, the optimum operating temperature of this sensor to 1000 ppm acetaldehyde vapor decreased from 180 °C to 100 °C comparing with that of pure WO{sub 3}. The response time and the recovery time for 100 ppm acetaldehyde vapor were 250 s and 225 s, respectively.

  17. Effect of Nanoparticle Size on Gas-sensing Properties of Tin Dioxide Sensors

    Institute of Scientific and Technical Information of China (English)

    XU Hong-yan; CUI De-liang; CAO Bing-qiang

    2012-01-01

    Sn(OH)4 was prepared by the conventional solution precipitate method,followed by supercritical CO2 drying.The resultant Sn(OH)4 was divided into three aliquots and calcined at 400,600 and 800 ℃,respectively,thus SnO2 nanoparticles with average crystallite sizes of 5,10 and 25 nm were obtained.Furthermore,three SnO2 thick film gas sensors(denoted as sensors S-400,S-600 and S-800) were fabricated from the above SnO2 nanoparticles.The adhesion of sensing materials on the surface of alumina tube is good.Compared to the sensors S-600 and S-800,sensor S-400 showed a much higher sensitivity to 1000 μL/L ethanol.On the other hand,sensor S-800 showed a much lower intrinsic resistance and improved selectivity to ethanol than sensors S-400 and S-600.X-Ray diffraction(XRD),transmission electron microscopy(TEM) and selective area electron diffraction(SAED) measurements were used to characterize the SnO2 nanoparticles calcined at different temperatures.The differences in the gas sensing performance of these sensors were analyzed on the basis of scanning electron microscopy(SEM).

  18. Reforming Gas Acetylene and Ammonia Compressor%氨乙炔混合气压缩机改造

    Institute of Scientific and Technical Information of China (English)

    胡晓东; 陈妙芳; 王正鲁

    2012-01-01

    针对MW50/28-298型氨乙炔混合气无油润滑压缩机设计缺陷导致排气量不足、使用寿命短等问题进行了理论和实验分析,在此基础上,提出了对压缩机无油润滑、活塞体结构的改造。实践证明:改造后的压缩机其微量油润滑对混合气体质量无影响,各项性能指标优越设计要求,使用寿命大大提高,这说明改造压缩机微量油润滑及活塞体结构是符合氨乙炔混合气压缩机的设计要求。%We believe there are some deficiencies in the design of the MW50/28-298-type gas aetylene and amonia compressor with oil-free lubrication, for example lower air discharging capacity and short service life. Hence, we propose reforming the oil-free lubrication and piston structure of the gas aetylene and amonia compresso with theo- retical and experimental analysis. The experimental results show that a small quantity of lubrication oil contained in the compressor thus reformed has no influence on the mixed gas quality and that the reformed compressor's perform- ance is better than that of the existing design; thus its service life is greatly enhanced.

  19. Chemical bonding and humidity sensing properties of amorphous carbon nitride (a-CNx) by acetylene gas

    Science.gov (United States)

    Aziz, Siti Aisyah Abd; Purhanudin, Noorain; Awang, Rozidawati

    2017-05-01

    Amorphous carbon nitride (a-CNx) thin films were deposited by radio frequency plasma enhance chemical vapor deposition (RF-PECVD) using a fixed mixture of acetylene (C2H2) at 20 sccm and nitrogen (N2) gases at 50 sccm. The films were deposited at different RF power of 60, 70, 80, 90 and 100 W. The deposition pressure, deposition time and substrate temperature were kept constant at 0.8 mbar, 30 minutes and 100°C, respectively. The chemical bonding of the a-CNx thin films was characterized using Fourier transform infrared spectroscopy (FTIR) and its sensing properties was determined using a home built humidity sensor system. The increase of RF powers leads to an increment of formation of double (C=N) and triple (C≡N) bonds as compared to a-CNx deposited using methane (CH4) or ethane (C2H6) gas. This is due to a higher ratio of C to H atoms in C2H2. The humidity sensing performance show the sensitivity of the films is the highest at low deposition power in changes of relative humidity (%RH). The a-CNx thin film show good repeatability and high sensitivity as a humidity sensing materials which prepared at low RF power.

  20. Tail Gas Treatment Measure in Ammonia Plant and Arrangement Gist for Flare System%氨厂尾气处理措施与火炬系统设置要点

    Institute of Scientific and Technical Information of China (English)

    张占一

    2013-01-01

    Author has analyzed the discharge situation of tail gas in large-sized synthetic ammonia plants under different conditions; has briefly de-scribed the appropriate treatment measures; has summarized the arrangement gist of flare system .%分析了大型合成氨厂不同工况下尾气的排放状况;简述了相应的处理措施;总结了火炬系统的设置要点。

  1. Flow synthesis using gaseous ammonia in a Teflon AF-2400 tube-in-tube reactor: Paal-Knorr pyrrole formation and gas concentration measurement by inline flow titration.

    Science.gov (United States)

    Cranwell, Philippa B; O'Brien, Matthew; Browne, Duncan L; Koos, Peter; Polyzos, Anastasios; Peña-López, Miguel; Ley, Steven V

    2012-08-14

    Using a simple and accessible Teflon AF-2400 based tube-in-tube reactor, a series of pyrroles were synthesised in flow using the Paal-Knorr reaction of 1,4-diketones with gaseous ammonia. An inline flow titration technique allowed measurement of the ammonia concentration and its relationship to residence time and temperature.

  2. Ammonia excitation imaging of shocked gas towards the W28 gamma-ray source HESS J1801-233

    CERN Document Server

    Maxted, Nigel I; Rowell, Gavin P; Nicholas, Brent P; Burton, Michael G; Walsh, Andrew; Fukui, Yasuo; Kawamura, Akiko

    2016-01-01

    We present 12 mm Mopra observations of the dense (>10^3 cm^-3 ) molecular gas towards the north-east (NE) of the W28 supernova remnant (SNR). This cloud is spatially well-matched to the TeV gamma-ray source HESS J1801-233 and is known to be a SNR-molecular cloud interaction region. Shock-disruption is evident from broad NH3 (1,1) spectral line-widths in regions towards the W28 SNR, while strong detections of spatially-extended NH3(3,3), NH3(4,4) and NH3(6,6) inversion emission towards the cloud strengthen the case for the existence of high temperatures within the cloud. Velocity dispersion measurements and NH3(n,n)/(1,1) ratio maps, where n=2, 3, 4 and 6, indicate that the source of disruption is from the side of the cloud nearest to the W28 SNR, suggesting that it is the source of cloud-disruption. Towards part of the cloud, the ratio of ortho to para-NH3 is observed to exceed 2, suggesting gas-phase NH3 enrichment due to NH3 liberation from dust grain mantles. The measured NH3 abundance with respect to H2 i...

  3. IFI16 and cGAS cooperate in the activation of STING during DNA sensing in human keratinocytes.

    Science.gov (United States)

    Almine, Jessica F; O'Hare, Craig A J; Dunphy, Gillian; Haga, Ismar R; Naik, Rangeetha J; Atrih, Abdelmadjid; Connolly, Dympna J; Taylor, Jordan; Kelsall, Ian R; Bowie, Andrew G; Beard, Philippa M; Unterholzner, Leonie

    2017-02-13

    Many human cells can sense the presence of exogenous DNA during infection though the cytosolic DNA receptor cyclic GMP-AMP synthase (cGAS), which produces the second messenger cyclic GMP-AMP (cGAMP). Other putative DNA receptors have been described, but whether their functions are redundant, tissue-specific or integrated in the cGAS-cGAMP pathway is unclear. Here we show that interferon-γ inducible protein 16 (IFI16) cooperates with cGAS during DNA sensing in human keratinocytes, as both cGAS and IFI16 are required for the full activation of an innate immune response to exogenous DNA and DNA viruses. IFI16 is also required for the cGAMP-induced activation of STING, and interacts with STING to promote STING phosphorylation and translocation. We propose that the two DNA sensors IFI16 and cGAS cooperate to prevent the spurious activation of the type I interferon response.

  4. Experimental study of electrical properties of ZnO nanowire random networks for gas sensing and electronic devices

    Science.gov (United States)

    Zhang, D.; Chava, S.; Berven, C.; Lee, S. K.; Devitt, R.; Katkanant, V.

    2010-07-01

    In this paper, we report on studying of ZnO nanowire mats as an electrical nanomaterial with particular interest in their interaction with various gas surroundings for gas sensing characteristics. The ZnO nanowires were synthesized on sapphire substrates using a horizontal tube furnace. The techniques of Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS) were applied to determine the as-grown ZnO nanowires’ morphological and crystal structures, chemical composition and electronic states. Four-terminal current-voltage (I-V) measurements were used to examine the electrical conductance of the ZnO nanowire mats exposed to various testing gases with reference to the vacuum condition. Gas exposure experiments were conducted in a custom-built environmental chamber, which was filled with different testing gases. We observed the current being significantly influenced with ambient CO gas. The I-V behavior of CO gas was also found to be reversible and repeatable after the chamber evacuation, which indicates that the ZnO nanowire mats can be used for gas sensing purposes. A possible interactive model of nanowires and testing gas molecules is proposed to elucidate the sensing selective and sensitive mechanism for gas sensors.

  5. Experimental study of electrical properties of ZnO nanowire random networks for gas sensing and electronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, D.; Lee, S.K.; Devitt, R.; Katkanant, V. [California State University, Fresno, Department of Physics, Fresno, CA (United States); Chava, S.; Berven, C. [University of Idaho, Department of Physics, Moscow (United States)

    2010-07-15

    In this paper, we report on studying of ZnO nanowire mats as an electrical nanomaterial with particular interest in their interaction with various gas surroundings for gas sensing characteristics. The ZnO nanowires were synthesized on sapphire substrates using a horizontal tube furnace. The techniques of Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS) were applied to determine the as-grown ZnO nanowires' morphological and crystal structures, chemical composition and electronic states. Four-terminal current-voltage (I-V) measurements were used to examine the electrical conductance of the ZnO nanowire mats exposed to various testing gases with reference to the vacuum condition. Gas exposure experiments were conducted in a custom-built environmental chamber, which was filled with different testing gases. We observed the current being significantly influenced with ambient CO gas. The I-V behavior of CO gas was also found to be reversible and repeatable after the chamber evacuation, which indicates that the ZnO nanowire mats can be used for gas sensing purposes. A possible interactive model of nanowires and testing gas molecules is proposed to elucidate the sensing selective and sensitive mechanism for gas sensors. (orig.)

  6. Application effects of coated urea and urease and nitrification inhibitors on ammonia and greenhouse gas emissions from a subtropical cotton field of the Mississippi delta region.

    Science.gov (United States)

    Tian, Zhou; Wang, Jim J; Liu, Shuai; Zhang, Zengqiang; Dodla, Syam K; Myers, Gerald

    2015-11-15

    Nitrogen (N) fertilization affects both ammonia (NH3) and greenhouse gas (GHG) emissions that have implications in air quality and global warming potential. Different cropping systems practice varying N fertilizations. The aim of this study was to investigate the effects of applications of polymer-coated urea and urea treated with N process inhibitors: NBPT [N-(n-butyl)thiophosphoric triamide], urease inhibitor, and DCD [Dicyandiamide], nitrification inhibitor, on NH3 and GHG emissions from a cotton production system in the Mississippi delta region. A two-year field experiment consisting of five treatments including the Check (unfertilized), urea, polymer-coated urea (ESN), urea+NBPT, and urea+DCD was conducted over 2013 and 2014 in a Cancienne loam (Fine-silty, mixed, superactive, nonacid, hyperthermic Fluvaquentic Epiaquepts). Ammonia and GHG samples were collected using active and passive chamber methods, respectively, and characterized. The results showed that the N loss to the atmosphere following urea-N application was dominated by a significantly higher emission of N2O-N than NH3-N and the most N2O-N and NH3-N emissions were during the first 30-50 days. Among different N treatments compared to regular urea, NBPT was the most effective in reducing NH3-N volatilization (by 58-63%), whereas DCD the most significant in mitigating N2O-N emissions (by 75%). Polymer-coated urea (ESN) and NBPT also significantly reduced N2O-N losses (both by 52%) over urea. The emission factors (EFs) for urea, ESN, urea-NBPT, urea+DCD were 1.9%, 1.0%, 0.2%, 0.8% for NH3-N, and 8.3%, 3.4%, 3.9%, 1.0% for N2O-N, respectively. There were no significant effects of different N treatments on CO2-C and CH4-C fluxes. Overall both of these N stabilizers and polymer-coated urea could be used as a mitigation strategy for reducing N2O emission while urease inhibitor NBPT for reducing NH3 emission in the subtropical cotton production system of the Mississippi delta region.

  7. Simonkolleite nano-platelets: Synthesis and temperature effect on hydrogen gas sensing properties

    Energy Technology Data Exchange (ETDEWEB)

    Sithole, J. [NANOAFNET, MRD-iThemba LABS, National Research Foundation,1 Old Faure road, Somerset West 7129 (South Africa); Dept. of Physics, University of Western Cape, Private Bag X 17, Belleville (South Africa); Ngom, B.D., E-mail: bdngom@tlabs.ac.za [NANOAFNET, MRD-iThemba LABS, National Research Foundation,1 Old Faure road, Somerset West 7129 (South Africa) and African Laser Centre, CSIR campus, P.O. Box 395, Pretoria (South Africa); Laboratoire de Photonique et de Nano-Fabrication, Groupe de Physique du Solide et Sciences des Materiaux, Departement de Physique Facultes des Sciences et Technique Universite Cheikh Anta Diop de Dakar, Dakar (Senegal); Khamlich, S. [NANOAFNET, MRD-iThemba LABS, National Research Foundation,1 Old Faure road, Somerset West 7129 (South Africa); African Laser Centre, CSIR campus, P.O. Box 395, Pretoria (South Africa); Manikanadan, E. [National Centre for Nano-Structured Materials (NCNSM), Council for Scientific and Industrial Research, Pretoria (South Africa); Manyala, N. [Department of Physics, SARCHI Chair in Carbon Technology and Materials, Institute of Applied Materials, University of Pretoria, Pretoria 0028 (South Africa); Saboungi, M.L. [Centre de Recherche sur la Matiere Divisee, CNRS-Orleans, Orleans (France); Knoessen, D. [Dept. of Physics, University of Western Cape, Private Bag X 17, Belleville (South Africa); Nemutudi, R.; Maaza, M. [NANOAFNET, MRD-iThemba LABS, National Research Foundation,1 Old Faure road, Somerset West 7129 (South Africa)

    2012-08-01

    In this work, the new refined mineral platelets-like morphology of simonkolleite based particles described by Shemetzer et al. (1985) were synthesized in zinc nitrate aqueous solution by a moderate solution process. The morphological and structural properties of the platelets-like Zn{sub 5}(OH){sub 8}Cl{sub 2}{center_dot}H{sub 2}O were characterized by scanning electron microscope energy dispersed X-ray spectroscopy, transmission electron microscope, powder X-ray diffraction and selected area electron diffraction as well as attenuated total reflection infrared spectroscopy. The morphology as well as the size in both basal and transversal directions of the simonkolleite Zn{sub 5}(OH){sub 8}Cl{sub 2}{center_dot}H{sub 2}O nano/micro crystals was found to be significantly depending on the specific concentration of 0.1 M of Zn{sup 2+}/Cl{sup -} ions in the precursor solution. The simonkolleite Zn{sub 5}(OH){sub 8}Cl{sub 2}{center_dot}H{sub 2}O nano-platelets revealed a significant and singular H{sub 2} gas sensing characteristics. The operating temperature was found to play a key role on the sensing properties of simonkolleite. The effect of temperature on the simonkolleite sample as a hydrogen gas sensor was studied by recording the change in resistivity of the film in presence of the test gas. The results on the sensitivity and response time as per comparison to earlier reported ZnO based sensors are indicated and discussed.

  8. Calcination-temperature-dependent gas-sensing properties of mesoporous α-Fe2O3 nanowires as ethanol sensors

    Science.gov (United States)

    Li, X. Q.; Li, D. P.; Xu, J. C.; Han, Y. B.; Jin, H. X.; Hong, B.; Ge, H. L.; Wang, X. Q.

    2017-07-01

    The mesoporous α-Fe2O3 nanowires (NWs) were successfully synthesized by changing the calcination temperature from 550 to 750 °C (marked NWs-550, NWs-650 and NWs-750) via using SBA-15 silica as the hard templates with the nanocasting method. The characterization results indicated that the bandgap of the as-prepared samples hardly changed and the high BET surface areas changed a little with the calcination temperature from 550 to 750 °C. Mesoporous α-Fe2O3 NWs had been found to possess the remarkable gas-sensing performance to ethanol gas. The gas-sensing behavior indicated that α-Fe2O3 NWs-650 exhibited the higher response than that of α-Fe2O3 NWs-550 and α-Fe2O3 NWs-750. The calcination-temperature-dependent gas-sensing properties were mainly attributed to the competition of surface defects and body defects by the crystallization temperature. The lower calcination temperature could create more surface defects to improve the gas-sensing response, while the higher temperature would reduce the body defect and make the charge carriers transport easily. As the result, the suitable calcination temperature was desired to optimize the defects of nanostructures to improve the gas sensitivity.

  9. WOOD COLOR CHANGES BY AMMONIA FUMING

    Directory of Open Access Journals (Sweden)

    Josip Miklečić,

    2012-06-01

    Full Text Available This paper studies the influence of ammonia gas on wood color changes in response to an increasing demand for dark colored wood specimens. The darker wood color in ammonia fuming is accomplished through chemical reactions between ammonia gas and wood compounds. We exposed oak, maple, spruce, and larch wood samples to ammonia gas for 16 days. During fuming, the color changes were studied using CIE L*a*b* parameters. After fuming, the changes in extractives content, tannin, and nitrogen content were analyzed. The chemical changes of wood and residues of wood extractives after fuming were analyzed by FTIR spectroscopy. Oak wood reacted intensively with ammonia gas in a very short time, and the darkening was prominent for all the investigated wood species. It was established that tannin had no major influence on color changes of maple and larch wood in the ammonia-fuming process. The FTIR spectra of fumed wood indicated involvement of carbonyl groups, and the FTIR spectra of wood extractives indicated involvement of carbonyl, aromatic, and alcohol groups in reaction with ammonia gas.

  10. Synthesis Methods, Microscopy Characterization and Device Integration of Nanoscale Metal Oxide Semiconductors for Gas Sensing in Aerospace Applications

    Science.gov (United States)

    VanderWal, Randy L.; Berger, Gordon M.; Kulis, Michael J.; Hunter, Gary W.; Xu, Jennifer C.; Evans, Laura J.

    2009-01-01

    A comparison is made between SnO2, ZnO, and TiO2 single-crystal nanowires and SnO2 polycrystalline nanofibers for gas sensing. Both nanostructures possess a one-dimensional morphology. Different synthesis methods are used to produce these materials: thermal evaporation-condensation (TEC), controlled oxidation, and electrospinning. Advantages and limitations of each technique are listed. Practical issues associated with harvesting, purification, and integration of these materials into sensing devices are detailed. For comparison to the nascent form, these sensing materials are surface coated with Pd and Pt nanoparticles. Gas sensing tests, with respect to H2, are conducted at ambient and elevated temperatures. Comparative normalized responses and time constants for the catalyst and noncatalyst systems provide a basis for identification of the superior metal-oxide nanostructure and catalyst combination. With temperature-dependent data, Arrhenius analyses are made to determine an activation energy for the catalyst-assisted systems.

  11. Simple Route to Obtain Nanostructured CeO2 Microspheres and CO Gas Sensing Performance

    Science.gov (United States)

    López-Mena, Edgar R.; Michel, Carlos R.; Martínez-Preciado, Alma H.; Elías-Zuñiga, Alex

    2017-03-01

    In this work, nanostructured CeO2 microspheres with high surface area and mesoporosity were prepared by the coprecipitation method, in absence of a template. The reaction between cerium nitrate and concentrated formic acid produced cerium formate, at room temperature. Further, calcination at 300 °C yielded single-phase CeO2 microspheres, with a diameter in the range 0.5-2.6 μm, the surface of these microspheres is completely nanostructured (diameter about 30-90 nm). CeO2 microspheres were used to fabricate a sensor device, and it was tested for intermediate CO gas concentrations (200-800 ppm). The detection of 200 ppm carbon monoxide was observed at 275 °C, with a response time of 9 s, using an applied frequency of 100 kHz. The detection of changes on the CO gas concentration was studied at different temperatures and applied frequencies. The results revealed a reproducible and stable gas sensing response.

  12. Trace-gas sensing using the compliance voltage of an external cavity quantum cascade laser

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Taubman, Matthew S.

    2013-06-04

    Quantum cascade lasers (QCLs) are increasingly being used to detect, identify, and measure levels of trace gases in the air. External cavity QCLs (ECQCLs) provide a broadly-tunable infrared source to measure absorption spectra of chemicals and provide high detection sensitivity and identification confidence. Applications include detecting chemical warfare agents and toxic industrial chemicals, monitoring building air quality, measuring greenhouse gases for atmospheric research, monitoring and controlling industrial processes, analyzing chemicals in exhaled breath for medical diagnostics, and many more. Compact, portable trace gas sensors enable in-field operation in a wide range of platforms, including handheld units for use by first responders, fixed installations for monitoring air quality, and lightweight sensors for deployment in unmanned aerial vehicles (UAVs). We present experimental demonstration of a new chemical sensing technique based on intracavity absorption in an external cavity quantum cascade laser (ECQCL). This new technique eliminates the need for an infrared photodetector and gas cell by detecting the intracavity absorption spectrum in the compliance voltage of the laser device itself. To demonstrate and characterize the technique, we measure infrared absorption spectra of chemicals including water vapor and Freon-134a. Sub-ppm detection limits in one second are achieved, with the potential for increased sensitivity after further optimization. The technique enables development of handheld, high-sensitivity, and high-accuracy trace gas sensors for in-field use.

  13. High reflected cubic cavity as long path absorption cell for infrared gas sensing

    Science.gov (United States)

    Yu, Jia; Gao, Qiang; Zhang, Zhiguo

    2014-10-01

    One direct and efficient method to improve the sensitivity of infrared gas sensors is to increase the optical path length of gas cells according to Beer-Lambert Law. In this paper, cubic shaped cavities with high reflected inner coating as novel long path absorption cells for infrared gas sensing were developed. The effective optical path length (EOPL) for a single cubic cavity and tandem cubic cavities were investigated based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) measuring oxygen P11 line at 763 nm. The law of EOPL of a diffuse cubic cavity in relation with the reflectivity of the coating, the port fraction and side length of the cavity was obtained. Experimental results manifested an increase of EOPL for tandem diffuse cubic cavities as the decrease of port fraction of the connecting aperture f', and the EOPL equaled to the sum of that of two single cubic cavities at f'<0.01. The EOPL spectra at infrared wavelength range for different inner coatings including high diffuse coatings and high reflected metallic thin film coatings were deduced.

  14. AIRBORNE, OPTICAL REMOTE SENSING OF METHANE AND ETHANE FOR NATURAL GAS PIPLINE LEAK DETECTION

    Energy Technology Data Exchange (ETDEWEB)

    Jerry Myers

    2004-05-12

    Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. The third six-month technical report contains a summary of the progress made towards finalizing the design and assembling the airborne, remote methane and ethane sensor. The vendor has been chosen and is on contract to develop the light source with the appropriate linewidth and spectral shape to best utilize the Ophir gas correlation software. Ophir has expanded upon the target reflectance testing begun in the previous performance period by replacing the experimental receiving optics with the proposed airborne large aperture telescope, which is theoretically capable of capturing many times more signal return. The data gathered from these tests has shown the importance of optimizing the fiber optic receiving fiber to the receiving optic and has helped Ophir to optimize the design of the gas cells and narrowband optical filters. Finally, Ophir will discuss remaining project issues that may impact the success of the project.

  15. Synthesis of Diacid-Assisted Indium Oxide Nanoparticles and Its CO Gas Sensing Activity.

    Science.gov (United States)

    Lee, Soo-Keun; Chang, Daeic; Yang, Seung Dae; Kim, Sang Wook

    2015-12-01

    Indium oxide (In2O3) is an extreme wide band-gap oxide material with unique electronic and optical properties that is used widely in solar cells, gas sensors and optoelectronic devices. In this study, two types of In2O3 nanostructures were prepared by a simple hydrothermal method using succinic acid (SA) or malonic acid (MA) as the assistant agents. The products were characterized by powder X-ray diffractions and scanning electron microscopy (SEM). SEM of the products showed that the In2O3 nanostructures prepared in the presence of SA have a typical cubic morphology with a length and height of -30 nm, whereas the In2O3 nanostructures synthesized in the presence of MA has an atypical rock shape, length and height of 30 -300 nm. Gas sensitivity measurements suggested that both In2O3 sensors (operated at 350 degrees C) have a good response to carbon monoxide (CO) compared to the commercial In2O3 nanoparticles. The SA-In2O3 sensor showed a shorter response time and stronger response than the MA-In2O3 sensor, suggesting that the improved gas sensing performance can be attributed mainly to the surface area.

  16. Effect of Sm on Gas-Sensing Properties of SnO2 with Different Oxygen Vacancy Concentrations

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The SnO2-x with different oxygen vacancy concentrations was modified by adding Sm. The modified SnO2-x was investigated by means of X-ray diffraction, X-ray photoelectron spectroscope, and scanning electron microscopy. Its gas-sensing properties to C2H6, C6H14, C2H5OH, CO, and H2 were studied too. The experiment results show that the gas-sensing properties of Sm/SnO2-x depend upon the amount of oxygen vacancies, therefore it is possible to improve gas-sensing properties of doped SnO2 by controlling its concentration of oxygen vacancy.

  17. The Preparation and Gas-sensing Property of Nanosize γ-Fe2O3/SiO2

    Institute of Scientific and Technical Information of China (English)

    马丽景; 闫涛; 白守礼; 黄小葳; 宋永吉; 陈霭璠; LIUChungChium

    2004-01-01

    Nanostructured γ-Fe2O3/SiO2 complex oxide was prepared by sol-gel method with tetraethoxysilane and iron nitrate as precursors. The particle size distribution, thermal and phase stabilities and gas sensing properties were systematically characterized by TEM, granularity distribution, TG-DTA, XRD and gas sensitivity measurements. The particle size is about 10 nm and size distribution is very narrow. The sensitivity of the sensing element to CO, H2, C2H4, C6H6 and the effects of calcination temperature on the sensitivity and conductance of gases were examined. The combination of excellent thermal stability and tunable gas sensing properties through careful control of the preparation and judicious selection of material compositions gives rise to novel nanocomposites, which is attractive for the sensitive and selective detection of reducing gases and some hydrocarbon gases.

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

    Science.gov (United States)

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

    2001-05-01

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

  19. DC Electrical Conductivity Retention, Optical Properties and Ammonia Sensing Analysis of Naturally Degraded CSA-Doped Graphene/polyaniline Composite Nanofibers Prepared with CTAB

    Science.gov (United States)

    Ghazali, Sayyed; Hossain, Muhammad M.; Khan, Abuzar; Khan, Mohd Y.; Hasan, Mudassir

    2016-09-01

    In this paper, we report surfactant-mediated synthesis of camphor sulfonic acid (CSA)-doped polyaniline/graphene (PANI/GN) composite nanofibers as an electrical conductor and excellent ammonia sensor. The synthesis was mediated by cetyltrimethylammonium bromide as surfactant. The as-synthesized composite nanofibers were characterized by Raman spectroscopy, scanning electron microscopy, tunneling electron microscopy, x-ray diffraction, diffused reflectance spectroscopy and differential scanning calorimetry. The electrical conductivity of the CSA-doped PANI/GN composite nanofibers was found to be remarkably enhanced as compared to the CSA-doped PANI. The boost in electronic conductivity could be attributed to an improved electronic interaction between CSA-doped PANI backbone and GN present in the composite system. The naturally degraded CSA-doped PANI/GN composite nanofibers showed a decrease in electrical conductivity but worked as a good ammonia sensor in open atmospheric conditions.

  20. DC Electrical Conductivity Retention, Optical Properties and Ammonia Sensing Analysis of Naturally Degraded CSA-Doped Graphene/polyaniline Composite Nanofibers Prepared with CTAB

    Science.gov (United States)

    Ghazali, Sayyed; Hossain, Muhammad M.; Khan, Abuzar; Khan, Mohd Y.; Hasan, Mudassir

    2017-01-01

    In this paper, we report surfactant-mediated synthesis of camphor sulfonic acid (CSA)-doped polyaniline/graphene (PANI/GN) composite nanofibers as an electrical conductor and excellent ammonia sensor. The synthesis was mediated by cetyltrimethylammonium bromide as surfactant. The as-synthesized composite nanofibers were characterized by Raman spectroscopy, scanning electron microscopy, tunneling electron microscopy, x-ray diffraction, diffused reflectance spectroscopy and differential scanning calorimetry. The electrical conductivity of the CSA-doped PANI/GN composite nanofibers was found to be remarkably enhanced as compared to the CSA-doped PANI. The boost in electronic conductivity could be attributed to an improved electronic interaction between CSA-doped PANI backbone and GN present in the composite system. The naturally degraded CSA-doped PANI/GN composite nanofibers showed a decrease in electrical conductivity but worked as a good ammonia sensor in open atmospheric conditions.

  1. Nanocrystalline TiO2/SnO2 heterostructures for gas sensing.

    Science.gov (United States)

    Lyson-Sypien, Barbara; Kusior, Anna; Rekas, Mieczylaw; Zukrowski, Jan; Gajewska, Marta; Michalow-Mauke, Katarzyna; Graule, Thomas; Radecka, Marta; Zakrzewska, Katarzyna

    2017-01-01

    The aim of this research is to study the role of nanocrystalline TiO2/SnO2 n-n heterojunctions for hydrogen sensing. Nanopowders of pure SnO2, 90 mol % SnO2/10 mol % TiO2, 10 mol % SnO2/90 mol % TiO2 and pure TiO2 have been obtained using flame spray synthesis (FSS). The samples have been characterized by BET, XRD, SEM, HR-TEM, Mössbauer effect and impedance spectroscopy. Gas-sensing experiments have been performed for H2 concentrations of 1-3000 ppm at 200-400 °C. The nanomaterials are well-crystallized, anatase TiO2, rutile TiO2 and cassiterite SnO2 polymorphic forms are present depending on the chemical composition of the powders. The crystallite sizes from XRD peak analysis are within the range of 3-27 nm. Tin exhibits only the oxidation state 4+. The H2 detection threshold for the studied TiO2/SnO2 heterostructures is lower than 1 ppm especially in the case of SnO2-rich samples. The recovery time of SnO2-based heterostructures, despite their large responses over the whole measuring range, is much longer than that of TiO2-rich samples at higher H2 flows. TiO2/SnO2 heterostructures can be intentionally modified for the improved H2 detection within both the small (1-50 ppm) and the large (50-3000 ppm) concentration range. The temperature Tmax at which the semiconducting behavior begins to prevail upon water desorption/oxygen adsorption depends on the TiO2/SnO2 composition. The electrical resistance of sensing materials exhibits a power-law dependence on the H2 partial pressure. This allows us to draw a conclusion about the first step in the gas sensing mechanism related to the adsorption of oxygen ions at the surface of nanomaterials.

  2. Nanocrystalline TiO2/SnO2 heterostructures for gas sensing

    Science.gov (United States)

    Kusior, Anna; Rekas, Mieczylaw; Zukrowski, Jan; Gajewska, Marta; Michalow-Mauke, Katarzyna; Graule, Thomas; Radecka, Marta; Zakrzewska, Katarzyna

    2017-01-01

    The aim of this research is to study the role of nanocrystalline TiO2/SnO2 n–n heterojunctions for hydrogen sensing. Nanopowders of pure SnO2, 90 mol % SnO2/10 mol % TiO2, 10 mol % SnO2/90 mol % TiO2 and pure TiO2 have been obtained using flame spray synthesis (FSS). The samples have been characterized by BET, XRD, SEM, HR-TEM, Mössbauer effect and impedance spectroscopy. Gas-sensing experiments have been performed for H2 concentrations of 1–3000 ppm at 200–400 °C. The nanomaterials are well-crystallized, anatase TiO2, rutile TiO2 and cassiterite SnO2 polymorphic forms are present depending on the chemical composition of the powders. The crystallite sizes from XRD peak analysis are within the range of 3–27 nm. Tin exhibits only the oxidation state 4+. The H2 detection threshold for the studied TiO2/SnO2 heterostructures is lower than 1 ppm especially in the case of SnO2-rich samples. The recovery time of SnO2-based heterostructures, despite their large responses over the whole measuring range, is much longer than that of TiO2-rich samples at higher H2 flows. TiO2/SnO2 heterostructures can be intentionally modified for the improved H2 detection within both the small (1–50 ppm) and the large (50–3000 ppm) concentration range. The temperature T max at which the semiconducting behavior begins to prevail upon water desorption/oxygen adsorption depends on the TiO2/SnO2 composition. The electrical resistance of sensing materials exhibits a power-law dependence on the H2 partial pressure. This allows us to draw a conclusion about the first step in the gas sensing mechanism related to the adsorption of oxygen ions at the surface of nanomaterials. PMID:28144570

  3. Short communication: Impact of the intensity of milk production on ammonia and greenhouse gas emissions in Portuguese cattle farms

    Directory of Open Access Journals (Sweden)

    José Pereira

    2015-12-01

    Full Text Available The aim of this study was evaluate the relationship between the intensity of milk production for a wide range of Portuguese commercial cattle farms and NH3 and greenhouse gas (GHG emissions from manure management and enteric fermentation. A survey was carried out at 1471 commercial dairy cattle farms (Holstein-Friesian and the NH3, N2O and CH4 emissions at each stage of manure management were estimated as well as CH4 losses from enteric fermentation. Gaseous emissions were estimated by a mass flow approach and following the recommendations of IPCC guidelines. The manure management and enteric fermentation in a typical Portuguese cattle farm contributes with 7.5±0.15 g N/L milk produced as NH3 and 1.2±0.22 kg CO2 equivalent per litre of milk as GHG. Increasing milk production will significantly reduce NH3 and GHG emissions per litre of milk produced. It can be concluded that a win-win strategy for reducing NH3 and GHG emissions from dairy cattle farms will be the increase of milk production on these farms. This goal can be achieved by implementing animal breeding programs and improving feed efficiency in order to increase productivity.

  4. Effects of a high-fibre diet on ammonia and greenhouse gas emissions from gestating sows and fattening pigs

    Science.gov (United States)

    Philippe, François-Xavier; Laitat, Martine; Wavreille, José; Nicks, Baudouin; Cabaraux, Jean-François

    2015-05-01

    This study aims to measure under barn conditions the emissions of NH3, N2O, CH4 and CO2 associated with gestating sows (trial 1) and fattening pigs (trial 2) fed either a control diet (CTD) based on cereals or a high-fibre diet (HFD) based on sugar beet pulp (SBP). Three successive batches of 10 Belgian Landrace gestating sows were used for trial 1. Two successive batches of 24 Piétrain × Belgian Landrace fattening pigs were used for trial 2. Animals were kept on slatted floor. The gas emissions were measured by infrared photoacoustic detection and expressed per day and per livestock unit, equals to 500 kg body weight. Similar trends were observed for both animal types. With HFD, the NH3 emissions were reduced (27.2 vs. 36.5 g for the gestating sows, P sows, P sows and 2.1 g for fattening pigs, P > 0.05), and on CO2 emissions (around 6.0 kg for gestating sows and 9.1 kg for fattening pigs, P > 0.05). Most of manure parameters did not statistically differ regarding the treatment. Reproductive performance and body condition of the sows were not affected by the diet. However, growth performance and carcass traits of the HFD-fed fattening pigs were deteriorated compared to CTD.

  5. Disposable, Paper-Based, Inkjet-Printed Humidity and H2S Gas Sensor for Passive Sensing Applications

    Directory of Open Access Journals (Sweden)

    Abdul Quddious

    2016-12-01

    Full Text Available An inkjet-printed, fully passive sensor capable of either humidity or gas sensing is presented herein. The sensor is composed of an interdigitated electrode, a customized printable gas sensitive ink and a specialized dipole antenna for wireless sensing. The interdigitated electrode printed on a paper substrate provides the base conductivity that varies during the sensing process. Aided by the porous nature of the substrate, a change in relative humidity from 18% to 88% decreases the electrode resistance from a few Mega-ohms to the kilo-ohm range. For gas sensing, an additional copper acetate-based customized ink is printed on top of the electrode, which, upon reaction with hydrogen sulphide gas (H2S changes, both the optical and the electrical properties of the electrode. A fast response time of 3 min is achieved at room temperature for a H2S concentration of 10 ppm at a relative humidity (RH of 45%. The passive wireless sensing is enabled through an antenna in which the inner loop takes care of conductivity changes in the 4–5 GHz band, whereas the outer-dipole arm is used for chipless identification in the 2–3 GHz band.

  6. Disposable, Paper-Based, Inkjet-Printed Humidity and H2S Gas Sensor for Passive Sensing Applications

    KAUST Repository

    Quddious, Abdul

    2016-12-06

    An inkjet-printed, fully passive sensor capable of either humidity or gas sensing is presented herein. The sensor is composed of an interdigitated electrode, a customized printable gas sensitive ink and a specialized dipole antenna for wireless sensing. The interdigitated electrode printed on a paper substrate provides the base conductivity that varies during the sensing process. Aided by the porous nature of the substrate, a change in relative humidity from 18% to 88% decreases the electrode resistance from a few Mega-ohms to the kilo-ohm range. For gas sensing, an additional copper acetate-based customized ink is printed on top of the electrode, which, upon reaction with hydrogen sulphide gas (HS) changes, both the optical and the electrical properties of the electrode. A fast response time of 3 min is achieved at room temperature for a HS concentration of 10 ppm at a relative humidity (RH) of 45%. The passive wireless sensing is enabled through an antenna in which the inner loop takes care of conductivity changes in the 4-5 GHz band, whereas the outer-dipole arm is used for chipless identification in the 2-3 GHz band.

  7. Adsorption induced phase transition in Ti(Pc){sub 2} gas sensing films: A joint AFM-EDXR study

    Energy Technology Data Exchange (ETDEWEB)

    Generosi, A., E-mail: Amanda.generosi@ism.cnr.it [ISM-CNR, Area della Ricerca di Tor Vergata, Via Fosso del Cavaliere 100, 00133 Roma (Italy); Rossi Albertini, V. [ISM-CNR, Area della Ricerca di Tor Vergata, Via Fosso del Cavaliere 100, 00133 Roma (Italy); Pennesi, G. [ISM-CNR, Area di Ricerca di Montelibretti, Via Salaria Km.29.5, 00116 Monterotondo Scalo, Roma (Italy); Paci, B. [ISM-CNR, Area della Ricerca di Tor Vergata, Via Fosso del Cavaliere 100, 00133 Roma (Italy)

    2014-12-15

    The morphological properties of thin metal phthalocyanine films, used as active material in gas sensing devices, are studied. Morphological changes, such as bulk or surface phase transitions, are key phenomena, having a determinant influence on the final properties and stability of the materials and devices. In this work, we successfully prove that joint in-situ atomic force microscopy and Energy Dispersive X-ray Reflectivity can be used, not only to monitor the sensing activity of bi[phthalocyaninato(2-)]titanium(IV) films, but also as a powerful tool to disclose the physical-chemical process beneath the sensing activity. Indeed it is shown that NO{sub x} adsorption activates a phase transition in the TiPc{sub 2} film, characterized by an oscillating behavior between two metastable states. Such phenomena endure as long as the gas molecules are present, finally evolving into the thermodynamically most stable phase. Fourier transform infrared spectroscopy analysis supports the above conclusions. - Highlights: • The NO{sub x} gas/TiPc{sub 2} sensing film interaction is investigated in real time. • Simultaneous EDXR/AFM techniques disclose a phase transition in the sensing material. • An oscillating α to β{sub 1} phase transition is induced by the presence of NO{sub x} molecules. • When the sensing process is concluded, the material turns to the most stable phase.

  8. Hydrogen Gas Sensing Based on SnO2 Nanostructure Prepared by Sol-Gel Spin Coating Method

    Science.gov (United States)

    Kadhim, Imad H.; Abu Hassan, H.

    2016-12-01

    A novel H2 gas sensor based on a SnO2 nanostructure was operated at room temperature (RT) (25°C). The SnO2 nanostructure was grown on Al2O3 substrates by a sol-gel spin coating method. The structural characteristics, surface morphology, and gas sensing properties of the SnO2 nanostructure were investigated. Thin film annealing at 500°C produced a high-quality SnO2 nanostructure with a crystallite size of 33.98 nm. A metal-semiconductor-metal gas sensor was fabricated using the SnO2 nanostructure and palladium metal. The gas sensor exhibited a sensitivity of 2570% to 1000 ppm H2 gas at RT. The sensing measurements for H2 gas at different temperatures (RT to 125°C) were repeatable for 50 min. Sensor sensitivity was tested under different H2 concentrations (150 ppm, 250 ppm, 375 ppm, 500 ppm, and 1000 ppm) at different operating temperatures. Adding glycerin to the sol solution increased the porosity of the SnO2 nanostructure surface, which increased the adsorption/desorption of gas molecules which leads to the high sensitivity of the sensor. Therefore, this H2 gas sensor is a suitable portable RT gas sensor.

  9. Hydrogen Gas Sensing Based on SnO2 Nanostructure Prepared by Sol-Gel Spin Coating Method

    Science.gov (United States)

    Kadhim, Imad H.; Abu Hassan, H.

    2017-03-01

    A novel H2 gas sensor based on a SnO2 nanostructure was operated at room temperature (RT) (25°C). The SnO2 nanostructure was grown on Al2O3 substrates by a sol-gel spin coating method. The structural characteristics, surface morphology, and gas sensing properties of the SnO2 nanostructure were investigated. Thin film annealing at 500°C produced a high-quality SnO2 nanostructure with a crystallite size of 33.98 nm. A metal-semiconductor-metal gas sensor was fabricated using the SnO2 nanostructure and palladium metal. The gas sensor exhibited a sensitivity of 2570% to 1000 ppm H2 gas at RT. The sensing measurements for H2 gas at different temperatures (RT to 125°C) were repeatable for 50 min. Sensor sensitivity was tested under different H2 concentrations (150 ppm, 250 ppm, 375 ppm, 500 ppm, and 1000 ppm) at different operating temperatures. Adding glycerin to the sol solution increased the porosity of the SnO2 nanostructure surface, which increased the adsorption/desorption of gas molecules which leads to the high sensitivity of the sensor. Therefore, this H2 gas sensor is a suitable portable RT gas sensor.

  10. Orbital remote sensing for geological mapping in southern Tunisia: Implication for oil and gas exploration

    Science.gov (United States)

    Peña, Sherrie A.; Abdelsalam, Mohamed G.

    2006-02-01

    mapping and seismic exploration. Identifying lithological and structural features using remote sensing studies incorporated with surface and sub-surface geological investigations in southern Tunisia can aid exploration for new oil and gas fields. Such an approach of integrating remote sensing and in situ geological studies can be successfully adopted in other parts of North Africa and arid regions in general.

  11. Integration and Testing of Miniaturized Volcanic Gas-Sensing Instruments on UAS Platforms

    Science.gov (United States)

    Lopez, T. M.; Kern, C.; Diaz, J. A.; Vanderwaal, S. J.; Levy, A.

    2015-12-01

    Volcanologists measure the concentrations and emission rates of gases emitted from active volcanoes to understand magmatic processes, which aids in eruption forecasting, and to evaluate air quality for human and environmental health. Both of these applications become particularly important during periods of unusually high volcanic unrest when it is typically hazardous to approach a given volcano. Unmanned aerial systems (UASs) represent a promising platform for continued gas measurements during unrest, while reducing the risk to volcanologists. Two miniature gas-sensing instruments have been developed specifically for integration onto small UAS platforms. Both instruments weigh 1 kg or less, including integrated power. The microDOAS instrument is an upward-looking UV/vis spectrometer that measures the spectral absorption signature of SO2 and certain halogen oxides in scattered solar radiation. By flying beneath a volcanic plume, the instrument can measure the SO2 content in the plume cross-section which can be used to determine the SO2 emission rate. The miniGas instrument is flown within the volcanic plume and records in situ concentrations of CO2, SO2 and H2S, as well as atmospheric temperature, pressure, relative humidity and GPS location. All data are telemetered back to the base station to immediately alert the operator of potentially hazardous conditions. Both instruments have been successfully tested at active volcanoes in Alaska and Costa Rica and were integrated onto small ACUASI Ptarmigan hexacopters. A test mission was conducted at the Poker Flat Research Range in Alaska. During this experiment both instruments were successfully flown in flight patterns typical of manned volcanic gas measurements and new UAV-specific measurement strategies were developed. Here we describe the instruments and platforms employed, our experimental results and observations, and make recommendations for application to volcanic settings.

  12. Remote sensing for gas plume monitoring using state-of-the-art infrared hyperspectral imaging

    Science.gov (United States)

    Hinnrichs, Michele

    1999-02-01

    Under contract to the US Air Force and Navy, Pacific Advanced Technology has developed a very sensitive hyperspectral imaging infrared camera that can perform remote imaging spectro-radiometry. One of the most exciting applications for this technology is in the remote monitoring of gas plume emissions. Pacific Advanced Technology (PAT) currently has the technology available to detect and identify chemical species in gas plumes using a small light weight infrared camera the size of a camcorder. Using this technology as a remote sensor can give advanced warning of hazardous chemical vapors undetectable by the human eye as well as monitor the species concentrations in a gas plume from smoke stack and fugitive leaks. Some of the gas plumes that have been measured and species detected using an IMSS imaging spectrometer are refinery smoke stacks plumes with emission of CO2, CO, SO2, NOx. Low concentration vapor unseen by the human eye that has been imaged and measured is acetone vapor evaporating at room temperature. The PAT hyperspectral imaging sensor is called 'Image Multi-spectral Sensing or IMSS.' The IMSS instrument uses defractive optic technology and exploits the chromatic aberrations of such lenses. Using diffractive optics for both imaging and dispersion allows for a very low cost light weight robust imaging spectrometer. PAT has developed imaging spectrometers that span the spectral range from the visible, midwave infrared (3 to 5 microns) and longwave infrared (8 to 12 microns) with this technology. This paper will present the imaging spectral data that we have collected on various targets with our hyperspectral imaging instruments as will also describe the IMSS approach to imaging spectroscopy.

  13. Characterization and Gas Sensing Properties of Copper-doped Tin Oxide Thin Films Deposited by Ultrasonic Spray Pyrolysis

    Directory of Open Access Journals (Sweden)

    Zhaoxia ZHAI

    2016-05-01

    Full Text Available Tin oxide-based thin films are deposited by ultrasonic spray pyrolysis technology, in which Cu addition is introduced to enhance the gas sensing performance by H2S detection. The thin films are porous and comprise nano-sized crystallites. One of the Cu-containing thin film sensors demonstrates a fast and significant response to H2S gas. The values of power law exponent n are calculated to discuss the sensitivity of the sensors, which is significantly promoted by Cu additive. The sensitivity of Cu-doped SnO2 gas sensors is determined by two mechanisms. One is the normal gas sensing mechanism of SnO2 grains, and the other is the promoted mechanism caused by the transformation between CuO and CuS in the H2S detection. DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12917

  14. SDS-assisted hydrothermal synthesis of NiO flake-flower architectures with enhanced gas-sensing properties

    Science.gov (United States)

    Miao, Ruiyang; Zeng, Wen; Gao, Qi

    2016-10-01

    A facile hydrothermal route was developed for the preparation of well-aligned hierarchical flower-like NiO nanostructure with the assistance of SDS that served as a structure-directing agent as well as a capping agent in the process of aggregation and assembly. Notably, the NiO sensors exhibit enhanced gas-sensing performance towards ethanol, which could be explained in association with the ultrathin nanosheets that are close to Debye length (LD) scale and thus get the majority carriers fully depleted due to the ionization of adsorbed oxygen, abundant effective gas diffusion paths as well as high surface-to-volume ratio to promote sufficient contact and reaction between the NiO sample and ethanol molecules, and numerous miniature reaction rooms assembled with nanosheets to make the test gas molecules stay long enough for completed gas-sensing reactions. Besides, a novel growth mechanism with the passage of reaction time was also proposed in detail.

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

    Directory of Open Access Journals (Sweden)

    Muhammad B. Haider

    2012-02-01

    Full Text Available 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.

  16. Effects of surface roughness on hydrogen gas sensing properties of single Pd nanowires.

    Science.gov (United States)

    Lee, Jun Min; Lee, Wooyoung

    2011-03-01

    We report on the effects of surface roughness resulting from an ion milling technique on the hydrogen gas sensing performance of a single Pd nanowire grown by electrodeposition into nanochannels in anodized aluminum oxide templates. A combination of electron beam lithography and a lift-off process was utilized to fabricate four-terminal devices based on individual Pd nanowires. These results are the first demonstration of the effect of ion milling on the response time in a single Pd nanowire used as a hydrogen sensor. The response time of the single Pd nanowire surface-treated by ion milling was 20 times faster than that of a sample without surface treatment. The faster response time was due to the surface roughness effects of the surface treatment, an increase in the surface-to-volume ratio of the ion-milled nanowire.

  17. Polypyrrole nanoparticles fabricated via Triton X-100 micelles template approach and their acetone gas sensing property

    Energy Technology Data Exchange (ETDEWEB)

    Li, Fake; Li, Hang [Department of Clinical Laboratory Medcine, Research Institute of Surgery, Daping Hospital, Third Military Medical University, Chongqing 400042 (China); Jiang, Hongmin [26th Research Institute, Chinese Electronics Scientific and Technical Group Company, Chongqing 400060 (China); Zhang, Kejun; Chang, Kai; Jia, Shuangrong; Jiang, Wenbin; Shang, Ya; Lu, Weiping [Department of Clinical Laboratory Medcine, Research Institute of Surgery, Daping Hospital, Third Military Medical University, Chongqing 400042 (China); Deng, Shaoli, E-mail: dengsl072@yahoo.com.cn [Department of Clinical Laboratory Medcine, Research Institute of Surgery, Daping Hospital, Third Military Medical University, Chongqing 400042 (China); Chen, Ming, E-mail: chenming1971@yahoo.com [Department of Clinical Laboratory Medcine, Research Institute of Surgery, Daping Hospital, Third Military Medical University, Chongqing 400042 (China)

    2013-09-01

    Nano-scaled polypyrrole (PPy) particles have been successfully synthesized with the help of Triton X-100 micelles via soft template approach. The polypyrrole nanoparticles have been spin-coated on surface acoustic wave (SAW) transducers to demonstrate their sensing capability toward acetone gas exposure. Field Emission Scanning Electron Microscopes (FE-SEM) and Fourier transform infrared (FT-IR) spectroscopy have been utilized to characterize these PPy nanoparticles. The PPy nanoparticles have an average diameter of 95 nm. The responses of the sensors are linearly associated with the acetone concentrations in the range from 5.5 ppm to 80 ppm. In response to 5.5 ppm acetone exposure, the response and recovery time are 9 s and 8.3 s, respectively. SAW sensors coated with PPy nanoparticles were potentially useful to detect acetone.

  18. Hydrogen gas sensors from polysilicon nanobelt devices selectively modified with sensing materials

    Science.gov (United States)

    Tran, Nhan Ai; Pan, Fu-Ming; Sheu, Jeng-Tzong

    2016-12-01

    Double-junction n+/n-/n+ polysilicon nanobelts featuring selectively deposited sensing materials have been investigated for application as H2 gas sensors. The selective modification of the devices was performed through a combination of localized ablation of a resist and lift-off of a previous catalyst material deposited through e-beam evaporation. Four nanobelt devices, differentiated by their doping concentrations at the n- region (from 2.5 × 1013 to 2.5 × 1014 cm-2), were analyzed in terms of the responses to H2 and their self-heating effects. A low doping concentration improved the response at room temperature, owing to a longer Debye length. The variation in the H2-induced surface potential associated with temperature, accounting for degradation in the response of the nanobelts with Joule heating bias, was analyzed in terms of the I-V characteristics of the double-junction device. Among various catalysts (Pt, Pd, Pt/Pd) evaluated for their H2 sensing characteristics, an ultrathin film of Pt/Pd was most favorable.

  19. Polyaniline-Cadmium Ferrite Nanostructured Composite for Room-Temperature Liquefied Petroleum Gas Sensing

    Science.gov (United States)

    Kotresh, S.; Ravikiran, Y. T.; Tiwari, S. K.; Vijaya Kumari, S. C.

    2017-08-01

    We introduce polyaniline-cadmium ferrite (PANI-CdFe2O4) nanostructured composite as a room-temperature-operable liquefied petroleum gas (LPG) sensor. The structure of PANI and the composite prepared by chemical polymerization was characterized by Fourier-transform infrared (FT-IR) spectroscopy, x-ray diffraction (XRD) analysis, and field-emission scanning electron microscopy. Comparative XRD and FT-IR analysis confirmed CdFe2O4 embedded in PANI matrix with mutual interfacial interaction. The nanostructure of the composite was confirmed by transmission electron microscopy. A simple LPG sensor operable at room temperature, exclusively based on spin-coated PANI-CdFe2O4 nanocomposite, was fabricated with maximum sensing response of 50.83% at 1000 ppm LPG. The response and recovery time of the sensor were 50 s and 110 s, respectively, and it was stable over a period of 1 month with slight degradation of 4%. The sensing mechanism is discussed on the basis of the p- n heterojunction barrier formed at the interface of PANI and CdFe2O4.

  20. Metal Decoration Effects on the Gas-Sensing Properties of 2D Hybrid-Structures on Flexible Substrates

    Directory of Open Access Journals (Sweden)

    Byungjin Cho

    2015-09-01

    Full Text Available We have investigated the effects of metal decoration on the gas-sensing properties of a device with two-dimensional (2D molybdenum disulfide (MoS2 flake channels and graphene electrodes. The 2D hybrid-structure device sensitively detected NO2 gas molecules (>1.2 ppm as well as NH3 (>10 ppm. Metal nanoparticles (NPs could tune the electronic properties of the 2D graphene/MoS2 device, increasing sensitivity to a specific gas molecule. For instance, palladium NPs accumulate hole carriers of graphene/MoS2, electronically sensitizing NH3 gas molecules. Contrarily, aluminum NPs deplete hole carriers, enhancing NO2 sensitivity. The synergistic combination of metal NPs and 2D hybrid layers could be also applied to a flexible gas sensor. There was no serious degradation in the sensing performance of metal-decorated MoS2 flexible devices before/after 5000 bending cycles. Thus, highly sensitive and endurable gas sensor could be achieved through the metal-decorated 2D hybrid-structure, offering a useful route to wearable electronic sensing platforms.

  1. Metal Decoration Effects on the Gas-Sensing Properties of 2D Hybrid-Structures on Flexible Substrates.

    Science.gov (United States)

    Cho, Byungjin; Yoon, Jongwon; Lim, Sung Kwan; Kim, Ah Ra; Choi, Sun-Young; Kim, Dong-Ho; Lee, Kyu Hwan; Lee, Byoung Hun; Ko, Heung Cho; Hahm, Myung Gwan

    2015-09-25

    We have investigated the effects of metal decoration on the gas-sensing properties of a device with two-dimensional (2D) molybdenum disulfide (MoS₂) flake channels and graphene electrodes. The 2D hybrid-structure device sensitively detected NO₂ gas molecules (>1.2 ppm) as well as NH₃ (>10 ppm). Metal nanoparticles (NPs) could tune the electronic properties of the 2D graphene/MoS₂ device, increasing sensitivity to a specific gas molecule. For instance, palladium NPs accumulate hole carriers of graphene/MoS₂, electronically sensitizing NH₃ gas molecules. Contrarily, aluminum NPs deplete hole carriers, enhancing NO₂ sensitivity. The synergistic combination of metal NPs and 2D hybrid layers could be also applied to a flexible gas sensor. There was no serious degradation in the sensing performance of metal-decorated MoS₂ flexible devices before/after 5000 bending cycles. Thus, highly sensitive and endurable gas sensor could be achieved through the metal-decorated 2D hybrid-structure, offering a useful route to wearable electronic sensing platforms.

  2. Optical Thin Films for Gas Sensing in Advanced Coal Fired Power Plants

    Energy Technology Data Exchange (ETDEWEB)

    Ohodnicki, Paul; Brown, Thomas; Baltrus John; Chorpening, Benjamin

    2012-08-09

    Even for existing coal based plants, the opportunity for sensors and controls to improve efficiency is great. A wide range of gas species are of interest for relevant applications. Functional sensor layers for embedded sensing must be compatible with extreme conditions (temperature, pressure, corrosive). Au incorporated metal oxides have been looked at by a number of other authors previously for gas sensing, but have often focused on temperatures below 500{degree}C. Au nanoparticle incorporated metal oxide thin films have shown enhanced gas sensing response. In prior work, we have demonstrated that material systems such as Au nanoparticle incorporated TiO{sub 2} films exhibit a potentially useful optical response to changing gas atmospheres at temperatures up to ~800-850{degree}C. Current work is focused on sputter-deposited Au/TiO{sub 2} films. Au and Ti are multi-layered sputter deposited, followed by a 950{degree}C oxidation step. Increasing Au layer thickness yields larger particles. Interband electronic transitions significantly modify the optical constants of Au as compared to the damped free electron theory. A high temperature oxidation (20%O{sub 2}/N{sub 2}) treatment was performed at 700{degree}C followed by a reduction (4%H{sub 2}/N{sub 2}) treatment to illustrate the shift in both absorption and scattering with exposure to reducing gases. Shift of localized surface plasmon resonance (LSPR) absorption peak in changing gas atmospheres is well documented, but shift in the peak associated with diffuse scattering is a new observation. Increasing Au layer-thickness results in an increase in LSPR absorption and a shift to longer wavelengths. Diffuse scattering associated with the LSPR resonance of Au shows a similar trend with increasing Au thickness. To model the temperature dependence of LSPR, the modification to the plasmon frequency, the damping frequency, and the dielectric constant of the oxide matrix must be accounted for. Thermal expansion of Au causes

  3. AIRBORNE, OPTICAL REMOTE SENSING OF METHANE AND ETHANE FOR NATURAL GAS PIPELINE LEAK DETECTION

    Energy Technology Data Exchange (ETDEWEB)

    Jerry Myers

    2003-11-12

    Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. This second six-month technical report summarizes the progress made towards defining, designing, and developing the hardware and software segments of the airborne, optical remote methane and ethane sensor. The most challenging task to date has been to identify a vendor capable of designing and developing a light source with the appropriate output wavelength and power. This report will document the work that has been done to identify design requirements, and potential vendors for the light source. Significant progress has also been made in characterizing the amount of light return available from a remote target at various distances from the light source. A great deal of time has been spent conducting laboratory and long-optical path target reflectance measurements. This is important since it helps to establish the overall optical output requirements for the sensor. It also reduces the relative uncertainty and risk associated with developing a custom light source. The data gathered from the optical path testing has been translated to the airborne transceiver design in such areas as: fiber coupling, optical detector selection, gas filters, and software analysis. Ophir will next, summarize the design progress of the transceiver hardware and software development. Finally, Ophir will discuss remaining project issues that may impact the success of the project.

  4. ZnO nanoflowers with single crystal structure towards enhanced gas sensing and photocatalysis.

    Science.gov (United States)

    Zhang, Sha; Chen, Hsueh-Shih; Matras-Postolek, Katarzyna; Yang, Ping

    2015-11-11

    In this paper, ZnO nanoflowers (NFs) were fabricated by thermal decomposition in an organic solvent and their application in gas sensors and photocatalysis was investigated. These single crystal ZnO NFs, which were observed for the first time, with an average size of ∼60 nm and were grown along the {100} facet. It was suggested that oleylamine used in the synthesis inhibited the growth and agglomeration of ZnO through the coordination of the oleylamine N atoms. The NFs exhibited excellent selectivity to acetone with a concentration of 25 ppm at 300 °C because they had a high specific surface area that provided more active sites and the surface adsorbed oxygen species for interaction with acetone. In addition, the ZnO NFs showed enhanced gas sensing response which was also ascribed to abundant oxygen vacancies at the junctions between petals of the NFs. Furthermore, ZnO-reduced graphene oxide (RGO) composites were fabricated by loading the ZnO NFs on the surface of the stratiform RGO sheet. In the photodegradation of rhodamine B tests, the composite revealed an enhanced photocatalytic performance compared with ZnO NFs under UV light irradiation.

  5. Characterization of Tungsten Oxide Thin Films Produced by Spark Ablation for NO2 Gas Sensing.

    Science.gov (United States)

    Isaac, Nishchay A; Valenti, Marco; Schmidt-Ott, Andreas; Biskos, George

    2016-02-17

    Tungsten oxides (WOx) thin films are currently used in electro-chromic devices, solar-cells and gas sensors as a result of their versatile and unique characteristics. In this study, we produce nanoparticulate WOx films by spark ablation and focused inertial deposition, and demonstrate their application for NO2 sensing. The primary particles in the as-deposited film samples are amorphous with sizes ranging from 10 to 15 nm. To crystallize the samples, the as-deposited films are annealed at 500 °C in air. This also caused the primary particles to grow to 30-50 nm by sintering. The morphologies and crystal structures of the resulting materials are studied using scanning and transmission electron microscopy and X-ray diffraction, whereas information on composition and oxidation states are determined by X-ray photoemission spectroscopy. The observed sensitivity of the resistance of the annealed films is ∼100 when exposed to 1 ppm of NO2 in air at 200 °C, which provides a considerable margin for employing them in gas sensors for measuring even lower concentrations. The films show a stable and repeatable response pattern. Considering the numerous advantages of spark ablation for fabricating nanoparticulate thin films, the results reported here provide a promising first step toward the production of high sensitivity and high accuracy sensors.

  6. Enhanced physical properties of porous silicon for improved hydrogen gas sensing

    Science.gov (United States)

    Naderi, N.; Hashim, M. R.; Amran, T. S. T.

    2012-05-01

    In the current communication, porous silicon samples were prepared by pulsed photoelectrochemical etching using a hydrofluoric acid-based solution. The structural and gas-sensing properties of the samples were studied. Apart from the cycle time T and pause time Toff of the pulsed current, a novel parameter, in the shape of the current named 'delay time Td' was introduced. Our results showed that by optimization of delay time, the porosity of samples can be controlled due to the chemical preparation of silicon surface prior to electrochemical anodization. The fourier-transform infrared measurements of porous silicon (PS) layers on Si substrate showed that the typical PS surface was characterized by chemical species like Si-H and Si-O-Si terminations. The two-minute delay before applying electrical current was considered sufficient for the fabrication of higher porosity (83%), more uniform, and more stable structures. The photoluminescence (PL) peak of the optimized sample showed higher intensity than the other samples. An obvious PL blue shift also revealed a change in the crystallographic characteristics of silicon due to quantum confinement effects. Metal-semiconductor-metal diodes with Schottky contacts of nickel were fabricated on PS samples and the potential application of optimized substrates for the improved sensitivity, stability, response time and recovery time of hydrogen gas sensors was subsequently studied.

  7. Synthesis and enhanced NO2 gas sensing properties of ZnO nanorods/TiO2 nanoparticles heterojunction composites.

    Science.gov (United States)

    Zou, C W; Wang, J; Xie, W

    2016-09-15

    ZnO nanorods/TiO2 nanoparticles composites were synthesized and the effects of TiO2 concentrations on the NO2 sensing properties were studied in detail. The as-prepared composites were characterized by XRD, SEM, TEM, PL, I-V and gas sensing measurements. The gas sensing results demonstrated that all the sensors based on ZnO/TiO2 nanocomposites exhibited much higher response than that of sensors based on pure ZnO nanorods. At the optimum operating temperature of 180°C, the response values of the sensors based on ZnO/TiO2 nanocomposites decorated with TiO2 concentrations of 0, 3, 5, 8 and 10wt% were 50, 140, 310, 350 and 258, respectively. The PL and I-V results indicated that the increased charge transfer between the ZnO nanorods mediated by TiO2 nanoparticles enhanced the conductivity of the ZnO/TiO2 nanocomposites. The gas sensing mechanism was also carefully analyzed. The attachment of TiO2 nanoparticles onto ZnO nanorods induced more active sites for the adsorption of oxygen molecules (O(2)) and O(2) which can be more easily adsorbed on the surface of ZnO nanorods. Furthermore, the conduction channel of ZnO/TiO2 was much narrower as a result of the formation of heterojunction which may further contribute to the enhanced NO2 sensing properties.

  8. TiO2(B) nanoparticle-functionalized WO3 nanorods with enhanced gas sensing properties.

    Science.gov (United States)

    Zhang, Hongxin; Wang, Shurong; Wang, Yanshuang; Yang, Jiedi; Gao, Xueling; Wang, Liwei

    2014-06-14

    In this work, TiO2(B) nanoparticle (NP)-functionalized WO3 nanorods (NRs) were synthesized by a two-step solution strategy, with a hydrothermal process for WO3 NRs and hydrolyzation of Ti(OBu)4 for the functionalization of TiO2(B) NPs. Various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were employed to investigate the morphology, microstructure, crystalline nature and chemical composition of the prepared TiO2(B) NP-functionalized WO3 NRs. SEM and TEM results revealed that the TiO2(B)-WO3 composite showed a rod-like nanostructure with a diameter in the range from 93 to 154 nm and a rough surface, which could increase the accessible surface area and the amount of surface active sites, thus improving the properties or performance of the as-prepared composite NRs. XRD and XPS analysis clearly verified that monoclinic TiO2(B) NPs, a metastable polymorph of TiO2, were successfully supported on the WO3 NRs. Gas sensing measurement results for several common reductive organic gases such as acetone, ethanol, ether, methanol and formaldehyde demonstrated that the sensor based on the as-obtained TiO2(B) NP-functionalized WO3 NRs exhibited obviously enhanced responses compared with a pure WO3 NR based sensor, as well as fast response-recovery speeds, good reproducibility and good stability, indicating their promising application in gas sensors. The excellent gas sensing performance could be attributed to the unique 1D rod-like nanostructure with a rough surface, the existence of TiO2-WO3 heterojunctions and the catalytic effect of the TiO2(B) NPs. The as-prepared TiO2(B) NP-functionalized WO3 NRs will also have very good prospects in electrochromic devices and catalysis applications.

  9. In Situ Monitoring of the Deposition of Flame-Made Chemoresistive Gas-Sensing Films.

    Science.gov (United States)

    Blattmann, Christoph O; Güntner, Andreas T; Pratsinis, Sotiris E

    2017-07-19

    Flame-deposited semiconducting nanomaterials on microelectronic circuitry exhibit exceptional performance as chemoresistive gas sensors. Current manufacturing technology, however, does not monitor in situ the formation of such nanostructured films, even though this can facilitate the controlled and economic synthesis of these sensors. Here, the resistance of such growing films is measured in situ during fabrication to monitor the creation of a semiconducting nanoparticle network for gas sensors. Upon formation of that network, the film resistance drops drastically to an asymptotic value that depends largely on the film structure or morphology rather than on its thickness and size of nanoparticle building blocks. Precursor solutions of various concentrations enable the flame deposition of Sb-doped SnO2 sensing films of different morphologies, each of which exhibit a characteristic in situ resistance pattern. Low precursor concentrations (1 mM) lead to thin (ca. 0.16 μm) films with slender columnar structures of increasing diameter (up to 25 nm) after prolonged deposition (up to 6 min) and show an oscillating in situ resistance during their fabrication. On the other extreme, high precursor concentrations (100 mM) lead to thick (up to 80 μm) dendritic and porous films consisting of nanoparticles with relatively small primary particle diameter (around 7 nm) that remain invariant of deposition duration, which is in agreement with the stable in situ resistance. Such dendritic films exhibit a sensor recovery time that is an order of magnitude longer than that of those made at lower concentrations. The above understanding enables the rapid and economic flame synthesis of thin gas sensors consisting of minimal semiconducting nanomaterial mass possessing a tuned baseline resistance and exhibiting excellent response to ethanol vapor.

  10. AIRBORNE, OPTICAL REMOTE SENSING OF METHANE AND ETHANE FOR NATURAL GAS PIPELINE LEAK DETECTION

    Energy Technology Data Exchange (ETDEWEB)

    Jerry Myers

    2003-05-13

    Ophir Corporation was awarded a contract by the U. S. Department of Energy, National Energy Technology Laboratory under the Project Title ''Airborne, Optical Remote Sensing of Methane and Ethane for Natural Gas Pipeline Leak Detection'' on October 14, 2002. This six-month technical report summarizes the progress for each of the proposed tasks, discusses project concerns, and outlines near-term goals. Ophir has completed a data survey of two major natural gas pipeline companies on the design requirements for an airborne, optical remote sensor. The results of this survey are disclosed in this report. A substantial amount of time was spent on modeling the expected optical signal at the receiver at different absorption wavelengths, and determining the impact of noise sources such as solar background, signal shot noise, and electronic noise on methane and ethane gas detection. Based upon the signal to noise modeling and industry input, Ophir finalized the design requirements for the airborne sensor, and released the critical sensor light source design requirements to qualified vendors. Responses from the vendors indicated that the light source was not commercially available, and will require a research and development effort to produce. Three vendors have responded positively with proposed design solutions. Ophir has decided to conduct short path optical laboratory experiments to verify the existence of methane and absorption at the specified wavelength, prior to proceeding with the light source selection. Techniques to eliminate common mode noise were also evaluated during the laboratory tests. Finally, Ophir has included a summary of the potential concerns for project success and has established future goals.

  11. Morphology-controlled preparation of tungsten oxide nanostructures for gas-sensing application

    Institute of Scientific and Technical Information of China (English)

    秦玉香; 刘长雨; 柳杨

    2015-01-01

    Novel three-dimensional (3D) hierarchical structure and roughly oriented one-dimensional (1D) nanowire of WO3 are selectively prepared on alumina substrate by an induced hydrothermal growth method. Each hierarchical structure is constructed hydrothermally through bilateral inductive growth of WO3 nanowire arrays from a nanosheet preformed on the substrate. Only roughly oriented 1D WO3 nanowire can be obtained from a spherical induction layer. The analyses show that as-prepared 1D nanowire and 3D hierarchical structures exhibit monoclinic and hexagonal phases of WO3, re-spectively. The gas-sensing properties of the nanowires and hierarchical structure of WO3, which include the variations of their resistances and response times when exposed to NO2, are investigated at temperatures ranging from room tempera-ture (20 ◦C) to 250 ◦C over 0.015 ppm–5 ppm NO2. The hierarchical WO3 behaves as a p-type semiconductor at room temperature, and shows p-to-n response characteristic reversal with the increase of temperature. Meanwhile, unlike the 1D nanowire, the hierarchical WO3 exhibits excellent response characteristic and very good reversibility and selectivity to NO2 gas at room temperature due to its unique microstructure. Especially, it is found that the hierarchical WO3-based sensor is capable of detecting NO2 at a ppb level with ultrashort response time shorter than 5 s, indicating the potential of this material in developing high sensitive gas sensor with low power consumption.

  12. Surface-area-controlled synthesis of porous TiO2 thin films for gas-sensing applications

    Science.gov (United States)

    Park, Jae Young; Kim, Ho-hyoung; Rana, Dolly; Jamwal, Deepika; Katoch, Akash

    2017-03-01

    Surface-area-controlled porous TiO2 thin films were prepared via a simple sol–gel chemical route, and their gas-sensing properties were thoroughly investigated in the presence of typical oxidizing NO2 gas. The surface area of TiO2 thin films was controlled by developing porous TiO2 networked by means of controlling the TiO2-to-TTIP (titanium isopropoxide, C12H28O4Ti) molar ratio, where TiO2 nanoparticles of size ∼20 nm were used. The sensor’s response was found to depend on the surface area of the TiO2 thin films. The porous TiO2 thin-film sensor with greater surface area was more sensitive than those of TiO2 thin films with lesser surface area. The improved sensing ability was ascribed to the porous network formed within the thin films by TiO2 sol. Our results show that surface area is a key parameter for obtaining superior gas-sensing performance; this provides important guidelines for preparing and using porous thin films for gas-sensing applications.

  13. Surface-area-controlled synthesis of porous TiO2 thin films for gas-sensing applications.

    Science.gov (United States)

    Park, Jae Young; Kim, Ho-Hyoung; Rana, Dolly; Jamwal, Deepika; Katoch, Akash

    2017-03-03

    Surface-area-controlled porous TiO2 thin films were prepared via a simple sol-gel chemical route, and their gas-sensing properties were thoroughly investigated in the presence of typical oxidizing NO2 gas. The surface area of TiO2 thin films was controlled by developing porous TiO2 networked by means of controlling the TiO2-to-TTIP (titanium isopropoxide, C12H28O4Ti) molar ratio, where TiO2 nanoparticles of size ∼20 nm were used. The sensor's response was found to depend on the surface area of the TiO2 thin films. The porous TiO2 thin-film sensor with greater surface area was more sensitive than those of TiO2 thin films with lesser surface area. The improved sensing ability was ascribed to the porous network formed within the thin films by TiO2 sol. Our results show that surface area is a key parameter for obtaining superior gas-sensing performance; this provides important guidelines for preparing and using porous thin films for gas-sensing applications.

  14. 甲醇弛放气制合成氨低负荷运行的解决措施%Solution Measure in Case of Operation with Low Load for Synthetic Ammonia Made by Methanol Releasing Gas

    Institute of Scientific and Technical Information of China (English)

    陈世通; 魏连坤; 徐会强

    2014-01-01

    针对山东恒昌聚材化工科技股份有限公司甲醇弛放气制合成氨长期低负荷运行的问题,介绍了新建两段炉、甲醇转化炉燃料气和化产管式炉燃料气改投解吸气等3种解决低负荷运行的解决措施。结果表明:甲醇弛放气由改造前的8600 m3/h增加到13500 m3/h,液氨产量提高了57.1%,基本保证了合成氨装置的满负荷运行。%In allusion to problems existed in long-term low load operation of synthetic ammonia made by methanol releasing gas in Shandong Hengchang Jucai Chemical Engineering & Science Technology Stock Company Ltd ., author has introduced the 3 kinds of solution measures in running of solving low load operation, making combustion gas used for new-built two stage furnace, methanol conventor and tube type furnace in operation to be changed to put into desorption gas and so on.Result indicates that methanol releasing gas is increased from 8 600 m3/h before reformation to 13 500 m3/h, liquid ammonia production is increased by 57.1%,it can guarantee basically full load operation for synthetic ammonia plant .

  15. Application effects of coated urea and urease and nitrification inhibitors on ammonia and greenhouse gas emissions from a subtropical cotton field of the Mississippi delta region

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Zhou [College of Resources and Environment, Northwest A& F University, Yangling, Shaanxi (China); School of Plant, Environment & Soil Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA 70803 (United States); Wang, Jim J., E-mail: jjwang@agcenter.lsu.edu [School of Plant, Environment & Soil Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA 70803 (United States); Liu, Shuai [College of Resources and Environment, Northwest A& F University, Yangling, Shaanxi (China); School of Plant, Environment & Soil Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA 70803 (United States); Zhang, Zengqiang, E-mail: zqzhang@nwsuaf.edu.cn [College of Resources and Environment, Northwest A& F University, Yangling, Shaanxi (China); Dodla, Syam K.; Myers, Gerald [School of Plant, Environment & Soil Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA 70803 (United States)

    2015-11-15

    Nitrogen (N) fertilization affects both ammonia (NH{sub 3}) and greenhouse gas (GHG) emissions that have implications in air quality and global warming potential. Different cropping systems practice varying N fertilizations. The aim of this study was to investigate the effects of applications of polymer-coated urea and urea treated with N process inhibitors: NBPT [N-(n-butyl)thiophosphoric triamide], urease inhibitor, and DCD [Dicyandiamide], nitrification inhibitor, on NH{sub 3} and GHG emissions from a cotton production system in the Mississippi delta region. A two-year field experiment consisting of five treatments including the Check (unfertilized), urea, polymer-coated urea (ESN), urea + NBPT, and urea + DCD was conducted over 2013 and 2014 in a Cancienne loam (Fine-silty, mixed, superactive, nonacid, hyperthermic Fluvaquentic Epiaquepts). Ammonia and GHG samples were collected using active and passive chamber methods, respectively, and characterized. The results showed that the N loss to the atmosphere following urea-N application was dominated by a significantly higher emission of N{sub 2}O-N than NH{sub 3}-N and the most N{sub 2}O-N and NH{sub 3}-N emissions were during the first 30–50 days. Among different N treatments compared to regular urea, NBPT was the most effective in reducing NH{sub 3}-N volatilization (by 58–63%), whereas DCD the most significant in mitigating N{sub 2}O-N emissions (by 75%). Polymer-coated urea (ESN) and NBPT also significantly reduced N{sub 2}O-N losses (both by 52%) over urea. The emission factors (EFs) for urea, ESN, urea-NBPT, urea + DCD were 1.9%, 1.0%, 0.2%, 0.8% for NH{sub 3}-N, and 8.3%, 3.4%, 3.9%, 1.0% for N{sub 2}O-N, respectively. There were no significant effects of different N treatments on CO{sub 2}-C and CH{sub 4}-C fluxes. Overall both of these N stabilizers and polymer-coated urea could be used as a mitigation strategy for reducing N{sub 2}O emission while urease inhibitor NBPT for reducing NH{sub 3} emission

  16. Determination of Content of Nitrate Removal of Ammonia in Ash of Boiler Flue Gas of Coal-ifred Units%燃煤机组锅炉烟气脱硝灰中氨含量测定

    Institute of Scientific and Technical Information of China (English)

    刘政修

    2015-01-01

    NOx is one of the main pollutants in the atmospheric environment, which is mainly from the thermal power generating units. Rely on low nitrogen combustion technology, far less than the emission requirements. Selective catalytic reduction (SCR) technology is the power plant flue gas DeNOx Technology is currently the most widely the highest efficiency and most mature, application. At present, online ammonia escape monitoring technology has many problems, affecting the ammonia escape the accuracy and stability of the monitoring data. In determining the type of fuel, furnace structure, the arrangement of heating surface, excess air, furnace air distribution and denitration catalyst type and other conditions, good control of ammonia addition amount and escape volume is the key to guarantee the NOx removal rate. Coal-fired boiler dust fly ash ammonia content can reflect the denitration ammonia escape rate conditions. According to foreign reports, under normal circumstances, the ammonia content in flue dust electricity is generally in the range of 50mg/kg-100mg/kg. The determination method of ammonia is no ash in domestic, no denitrification operation of fly ash containing ammonia affects the amount of accumulated data. In this paper, through a lot of experiments, the conditions of ammonia dissolved in ash determined (such as dissolution time, mixing state, cement water ratio, ash sample quantity and stability), developed methods for determination of ammonia in ash.%NOx是大气环境的主要污染物之一,其主要来源为火力发电机组。依靠低氮燃烧技术,远达不到排放要求。选择性催化还原脱硝(简称SCR)技术是目前效率最高、最成熟、应用最广泛的电厂烟气脱硝技术。目前,在线氨逃逸监测技术存在诸多问题,影响了氨逃逸监测数据的准确度和稳定性。在燃料种类、炉膛结构、受热面布置、过量空气量、炉膛气流分布以及脱硝催化剂类型等条件确定的情

  17. Methane gas sensing at relatively low operating temperature by hydrothermally prepared SnO{sub 2} nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Amutha, A. [Pondicherry University, Centre for Nanoscience and Technology (India); Amirthapandian, S. [Indira Gandhi Centre for Atomic Research, Materials Physics Division, Materials Science Group (India); Prasad, A. K. [Indira Gandhi Centre for Atomic Research, Surface and Nanoscience Division, Materials Science Group (India); Panigrahi, B. K. [Indira Gandhi Centre for Atomic Research, Materials Physics Division, Materials Science Group (India); Thangadurai, P., E-mail: thangadurai.p@gmail.com [Pondicherry University, Centre for Nanoscience and Technology (India)

    2015-07-15

    Tin oxide (SnO{sub 2}) nanorods were prepared by surfactant-free hydrothermal method and their methane gas sensing characteristics were studied. These SnO{sub 2} nanorods were characterized by XRD, SEM, TEM, EDS, EELS, UV–Visible, and Raman spectroscopies. The SnO{sub 2} nanorods were single crystalline possessing tetragonal rutile structure. Average diameter of the nanorods was in the range from 8 to 48 nm with an average length of 174 nm. The diameter of the nanorod was found to increase with the increase of reaction time. The E{sub g} and A{sub 1g} Raman modes showed a significant blue and red shift, respectively, and this was due to the contribution from the phonons with q ≠ 0 in the first Brillouin zone. Gas sensing measurements against methane gas showed a good sensitivity at an operating temperature of 100 °C, and the maximum gas sensitivity was observed at 175 °C. Our present experiments clearly demonstrate the sensitivity of methane up to 300 ppm at 100 °C, which is a lower operating temperature compared to the previously reported values. Hydrogen sensor was also fabricated with the same SnO{sub 2} nanorods and its performance was compared with the methane gas sensor. These rods show better sensitivity toward methane gas than hydrogen gas.

  18. Enhanced gas sensing performance of electrospun Pt-functionalized NiO nanotubes with chemical and electronic sensitization.

    Science.gov (United States)

    Fu, Jiecai; Zhao, Changhui; Zhang, Junli; Peng, Yong; Xie, Erqing

    2013-08-14

    Pt-functionalized NiO composite nanotubes were synthesized by a simple electrospinning method, and their morphology, chemistry, and crystal structure have been characterized at the nanoscale. It was found that the Pt nanoparticles were dispersed uniformly in the NiO nanotubes, and the Pt-functionalized NiO composite nanotubes showed some dendritic structure in the body of nanotubes just like thorns growing in the nanotubes. Compared with the pristine NiO nanotube based gas sensor and other NiO-based gas sensors reported previously, the Pt-functionalized NiO composite nanotube based gas sensor showed substantially enhanced electrical responses to target gas (methane, hydrogen, acetone, and ethanol), especially ethanol. The NiO-Pt 0.7% composite nanotube based gas sensor displayed a response value of 20.85 at 100 ppm at ethanol and 200 °C, whereas the pristine NiO nanotube based gas sensor only showed a response of 2.06 under the same conditions. Moreover, the Pt-functionalized NiO composite nanotube based gas sensor demonstrated outstanding gas selectivity for ethanol against methane, hydrogen, and acetone. The reason for which the Pt-functionalized NiO composite nanotube based gas sensor obviously enhanced the gas sensing performance is attributed to the role of Pt on the chemical sensitization (catalytic oxidation) of target gases and the electronic sensitization (Fermi-level shifting) of NiO.

  19. Preparation of nanostructured PbS thin films as sensing element for NO{sub 2} gas

    Energy Technology Data Exchange (ETDEWEB)

    Kaci, S., E-mail: k_samira05@yahoo.fr [Centre de Recherche en Technologie des Semi-conducteurs pour l’Energétique (CRTSE) Division Couches Minces et Interfaces, 02 Bd Frantz Fanon, B.P. 140, 7 Merveilles, 16038 Algiers (Algeria); Keffous, A.; Hakoum, S. [Centre de Recherche en Technologie des Semi-conducteurs pour l’Energétique (CRTSE) Division Couches Minces et Interfaces, 02 Bd Frantz Fanon, B.P. 140, 7 Merveilles, 16038 Algiers (Algeria); Trari, M. [Université des Sciences et Technologies Houari Boumediene (USTHB), Laboratoire de Stockage et de Valorisation des Eneriges Renouvelables, Faculté de Chimie, BP 32, EL Alia, 16111 Bab Ezzouar, Algiers (Algeria); Mansri, O.; Menari, H. [Centre de Recherche en Technologie des Semi-conducteurs pour l’Energétique (CRTSE) Division Couches Minces et Interfaces, 02 Bd Frantz Fanon, B.P. 140, 7 Merveilles, 16038 Algiers (Algeria)

    2014-06-01

    In this work, we demonstrate that semiconducting films of A{sub IV}B{sub VI} compounds, in particular, of nanostructured lead sulfide (PbS) which prepared by chemical bath deposition (CBD), can be used as a sensing element for nitrogen dioxide (NO{sub 2}) gas. The CBD method is versatile, simple in implementation and gives homogeneous semiconductor structures. We have prepared PbS nanocrystalline thin film at different reaction baths and temperatures. In the course of deposition, variable amounts of additives, such as organic substances among them, were introduced into the baths. The energy dispersive analysis (EDX) confirms the chemical composition of PbS films. A current–voltage (I–V) characterization of Pd/nc-PbS/a-SiC:H pSi(100)/Al Schottky diode structures were studied in the presence of NO{sub 2} gas. The gas sensing behavior showed that the synthesized PbS nanocrystalline thin films were influenced by NO{sub 2} gas at room temperature. The results can be used for developing an experimental sensing element based on chemically deposited nanostructured PbS films which can be applicable in gas sensors.

  20. Oil and gas reservoir exploration based on hyperspectral remote sensing and super-low-frequency electromagnetic detection

    Science.gov (United States)

    Qin, Qiming; Zhang, Zili; Chen, Li; Wang, Nan; Zhang, Chengye

    2016-01-01

    This paper proposes a method that combined hyperspectral remote sensing with super-low-frequency (SLF) electromagnetic detection to extract oil and gas reservoir characteristics from surface to underground, for the purpose of determining oil and gas exploration target regions. The study area in Xinjiang Karamay oil-gas field, China, was investigated. First, a Hyperion dataset was used to extract altered minerals (montmorillonite, chlorite, and siderite), which were comparatively verified by field survey and spectral measurement. Second, the SLF electromagnetic datasets were then acquired where the altered minerals were distributed. An inverse distance weighting method was utilized to acquire two-dimensional profiles of the electrical feature distribution of different formations on the subsurface. Finally, existing geological data, field work, and the results derived from Hyperion images and SLF electromagnetic datasets were comprehensively analyzed to confirm the oil and gas exploration target region. The results of both hyperspectral remote sensing and SLF electromagnetic detection had a good consistency with the geological materials in this study. This paper demonstrates that the combination of hyperspectral remote sensing and SLF electromagnetic detection is suitable for the early exploration of oil and gas reservoirs, which is characterized by low exploration costs, large exploration areas, and a high working efficiency.

  1. Improvement of NO Gas Sensing Properties of Polyaniline/MWCNT Composite by Photocatalytic Effect of TiO2

    Directory of Open Access Journals (Sweden)

    Jumi Yun

    2013-01-01

    Full Text Available The highly sensitive and rapid NO gas sensor was prepared with polyaniline/TiO2/carbon nanotube composites. Aniline was polymerized on the surface of carbon nanotube (p-type semiconductor with embedding TiO2. The gas sensing property was measured by the changes of electrical resistance without or with UV irradiation to investigate the photodegradation of NO by TiO2. The photo-degraded products such as HNO2, NO2, and HNO3, which were adsorbed on the PANi-coated carbon nanotubes, resulted in the decreased electrical resistance in the p-type semiconductors of carbon nanotube and polyaniline. The advantages of TiO2 photocatalyst in gas sensing were apparent in the improvement in both sensitivity and response rate.

  2. Gas Sensing Analysis of Ag-Decorated Graphene for Sulfur Hexafluoride Decomposition Products Based on the Density Functional Theory

    Science.gov (United States)

    Zhang, Xiaoxing; Huang, Rong; Gui, Yingang; Zeng, Hong

    2016-01-01

    Detection of decomposition products of sulfur hexafluoride (SF6) is one of the best ways to diagnose early latent insulation faults in gas-insulated equipment, and the occurrence of sudden accidents can be avoided effectively by finding early latent faults. Recently, functionalized graphene, a kind of gas sensing material, has been reported to show good application prospects in the gas sensor field. Therefore, calculations were performed to analyze the gas sensing properties of intrinsic graphene (Int-graphene) and functionalized graphene-based material, Ag-decorated graphene (Ag-graphene), for decomposition products of SF6, including SO2F2, SOF2, and SO2, based on density functional theory (DFT). We thoroughly investigated a series of parameters presenting gas-sensing properties of adsorbing process about gas molecule (SO2F2, SOF2, SO2) and double gas molecules (2SO2F2, 2SOF2, 2SO2) on Ag-graphene, including adsorption energy, net charge transfer, electronic state density, and the highest and lowest unoccupied molecular orbital. The results showed that the Ag atom significantly enhances the electrochemical reactivity of graphene, reflected in the change of conductivity during the adsorption process. SO2F2 and SO2 gas molecules on Ag-graphene presented chemisorption, and the adsorption strength was SO2F2 > SO2, while SOF2 absorption on Ag-graphene was physical adsorption. Thus, we concluded that Ag-graphene showed good selectivity and high sensitivity to SO2F2. The results can provide a helpful guide in exploring Ag-graphene material in experiments for monitoring the insulation status of SF6-insulated equipment based on detecting decomposition products of SF6. PMID:27809269

  3. Gas Sensing Analysis of Ag-Decorated Graphene for Sulfur Hexafluoride Decomposition Products Based on the Density Functional Theory

    Directory of Open Access Journals (Sweden)

    Xiaoxing Zhang

    2016-11-01

    Full Text Available Detection of decomposition products of sulfur hexafluoride (SF6 is one of the best ways to diagnose early latent insulation faults in gas-insulated equipment, and the occurrence of sudden accidents can be avoided effectively by finding early latent faults. Recently, functionalized graphene, a kind of gas sensing material, has been reported to show good application prospects in the gas sensor field. Therefore, calculations were performed to analyze the gas sensing properties of intrinsic graphene (Int-graphene and functionalized graphene-based material, Ag-decorated graphene (Ag-graphene, for decomposition products of SF6, including SO2F2, SOF2, and SO2, based on density functional theory (DFT. We thoroughly investigated a series of parameters presenting gas-sensing properties of adsorbing process about gas molecule (SO2F2, SOF2, SO2 and double gas molecules (2SO2F2, 2SOF2, 2SO2 on Ag-graphene, including adsorption energy, net charge transfer, electronic state density, and the highest and lowest unoccupied molecular orbital. The results showed that the Ag atom significantly enhances the electrochemical reactivity of graphene, reflected in the change of conductivity during the adsorption process. SO2F2 and SO2 gas molecules on Ag-graphene presented chemisorption, and the adsorption strength was SO2F2 > SO2, while SOF2 absorption on Ag-graphene was physical adsorption. Thus, we concluded that Ag-graphene showed good selectivity and high sensitivity to SO2F2. The results can provide a helpful guide in exploring Ag-graphene material in experiments for monitoring the insulation status of SF6-insulated equipment based on detecting decomposition products of SF6.

  4. Gas Sensing Analysis of Ag-Decorated Graphene for Sulfur Hexafluoride Decomposition Products Based on the Density Functional Theory.

    Science.gov (United States)

    Zhang, Xiaoxing; Huang, Rong; Gui, Yingang; Zeng, Hong

    2016-11-01

    Detection of decomposition products of sulfur hexafluoride (SF₆) is one of the best ways to diagnose early latent insulation faults in gas-insulated equipment, and the occurrence of sudden accidents can be avoided effectively by finding early latent faults. Recently, functionalized graphene, a kind of gas sensing material, has been reported to show good application prospects in the gas sensor field. Therefore, calculations were performed to analyze the gas sensing properties of intrinsic graphene (Int-graphene) and functionalized graphene-based material, Ag-decorated graphene (Ag-graphene), for decomposition products of SF₆, including SO₂F₂, SOF₂, and SO₂, based on density functional theory (DFT). We thoroughly investigated a series of parameters presenting gas-sensing properties of adsorbing process about gas molecule (SO₂F₂, SOF₂, SO₂) and double gas molecules (2SO₂F₂, 2SOF₂, 2SO₂) on Ag-graphene, including adsorption energy, net charge transfer, electronic state density, and the highest and lowest unoccupied molecular orbital. The results showed that the Ag atom significantly enhances the electrochemical reactivity of graphene, reflected in the change of conductivity during the adsorption process. SO₂F₂ and SO₂ gas molecules on Ag-graphene presented chemisorption, and the adsorption strength was SO₂F₂ > SO₂, while SOF₂ absorption on Ag-graphene was physical adsorption. Thus, we concluded that Ag-graphene showed good selectivity and high sensitivity to SO₂F₂. The results can provide a helpful guide in exploring Ag-graphene material in experiments for monitoring the insulation status of SF₆-insulated equipment based on detecting decomposition products of SF₆.

  5. Room temperature ferromagnetism and CH{sub 4} gas sensing of titanium oxynitride induced by milling and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Bolokang, Amogelang S., E-mail: Sylvester.Bolokang@transnet.net [DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria, 0001 (South Africa); Transnet Engineering, Product Development, Private Bag X 528, Kilnerpark, 0127 (South Africa); Tshabalala, Zamaswazi P. [DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria, 0001 (South Africa); Malgas, Gerald F. [Department of Physics, University of the Western Cape, Private Bag X17, Bellville, 7535 (South Africa); Kortidis, Ioannis [DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria, 0001 (South Africa); West Virginia University, Department of Mechanical & Aerospace Engineering, Evansdale Campus, Morgantown, WV, 26506 (United States); Swart, Hendrik C. [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein, ZA9300 (South Africa); Motaung, David E., E-mail: dmotaung@csir.co.za [DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria, 0001 (South Africa)

    2017-06-01

    We report on the room temperature ferromagnetism and CH{sub 4} gas sensing of titanium oxynitride prepared by milling and annealing at 1100 °C in a nitrogen gas environment. Structural analyses revealed a metastable orthorhombic TiO{sub 2} phase after milling for 120 h. The 120 h milled TiO{sub 2} particles and subsequently annealed in nitrogen gas at 1100 °C showed the formation of titanium oxynitride (TiO{sub x}N{sub y}) with a tetragonal crystal structure. An FCC metastable TiO{sub x}N{sub y} phase was also observed with a lattice parameter a = 4.235 Å. The vibrating sample magnetometer and electron paramagnetic analyses showed that the milled and TiO{sub x}N{sub y} samples possess room temperature ferromagnetism. Gas sensing measurements were carried out toward CH{sub 4} and H{sub 2} gases. The TiO{sub x}N{sub y} nanostructures demonstrated higher sensing response and selectivity to CH{sub 4} gas at room temperature. The enhanced response of 1010 and sensitivity of 50.12 ppm{sup -1} at a concentration of 20 ppm CH{sub 4} are associated with higher surface area, pore diameter and surface defects such as oxygen vacancies and Ti{sup 3+}, as evidenced from the Brunauer–Emmet–Teller, photoluminescence, electron paramagnetic resonance and x-ray photoelectron analyses. - Highlights: • Ball milled of TiO{sub 2} structure revealed metastable orthorhombic phase. • Upon nitridation tetragonal and FCC TiO{sub x}N{sub y} crystal structures were induced. • The magnetic properties of TiO{sub 2} nanoparticles was transformed by milling. • TiO{sub x}N{sub y} sensing response for CH{sub 4} gas at room temperature was high.

  6. TiO2-Based Nanomaterials for Gas Sensing-Influence of Anatase and Rutile Contributions.

    Science.gov (United States)

    Zakrzewska, K; Radecka, M

    2017-12-01

    The paper deals with application of three nanomaterial systems: undoped TiO2, chromium-doped TiO2:Cr and TiO2-SnO2 synthesized by flame spray synthesis (FSS) technique for hydrogen sensing. The emphasis is put on the role of anatase and rutile polymorphic forms of TiO2 in enhancing sensitivity towards reducing gases. Anatase-to-rutile transformation is achieved by annealing of undoped TiO2 in air at 700 °C, specific Cr doping and modification with SnO2. Undoped TiO2 and TiO2-SnO2 exhibit n-type behaviour and while TiO2: 5 at.% Cr is a p-type semiconductor. X-ray diffraction (XRD) has been applied to determine anatase-to-rutile weight ratio as well as anatase and rutile crystal size. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to characterize the structure and morphological parameters. Optical reflectometry enabled to find and compare the band gaps E g of anatase and rutile predominated compositions. Electrical properties, i.e. the electrical conductivity and values of constant phase element (CPE), have been established on the basis of impedance spectroscopy. Dynamic responses of the electrical resistance as a function of hydrogen concentration revealed that predominance of rutile in anatase/rutile mixture is beneficial for gas sensing. Partial transformation to rutile in all three material systems under study resulted in an increased sensitivity towards hydrogen. It is proposed that this effect can be explained in a similar way as in photocatalysis, i.e. by specific band alignment and electron transfer from rutile to anatase to facilitate oxygen preadsorption on the surface of anatase grains.

  7. Simulation and Fabrication of SAW-Based Gas Sensor with Modified Surface State of Active Layer and Electrode Orientation for Enhanced H2 Gas Sensing

    Science.gov (United States)

    Hasan, Md. Nazibul; Maity, Santanu; Sarkar, Argha; Bhunia, Chandan Tilak; Acharjee, Debabrata; Joseph, Aneesh M.

    2016-11-01

    The design, analysis, optimization, and fabrication of layered and nanostructure-based surface acoustic wave (SAW) gas sensors are presented. A lithium niobate and zinc oxide (ZnO) nano multilayer structure is proposed to enhance the sensitivity of the SAW-based gas sensor. Different materials are considered for the intermediate layer in the design for optimization purposes. The sensitivity of the sensor could be improved due to increased active surface area obtained by varying the aspect ratio of the nanorods, the thickness of the intermediate layer, and the gap between the electrodes. The total displacement and frequency shift of the device were significantly improved. Overall, the mechanically engineered surface-based (nanorod) SAW gas sensor offered better sensing response than the layered SAW gas sensor in terms of sensitivity performance.

  8. Simulation and Fabrication of SAW-Based Gas Sensor with Modified Surface State of Active Layer and Electrode Orientation for Enhanced H2 Gas Sensing

    Science.gov (United States)

    Hasan, Md. Nazibul; Maity, Santanu; Sarkar, Argha; Bhunia, Chandan Tilak; Acharjee, Debabrata; Joseph, Aneesh M.

    2017-02-01

    The design, analysis, optimization, and fabrication of layered and nanostructure-based surface acoustic wave (SAW) gas sensors are presented. A lithium niobate and zinc oxide (ZnO) nano multilayer structure is proposed to enhance the sensitivity of the SAW-based gas sensor. Different materials are considered for the intermediate layer in the design for optimization purposes. The sensitivity of the sensor could be improved due to increased active surface area obtained by varying the aspect ratio of the nanorods, the thickness of the intermediate layer, and the gap between the electrodes. The total displacement and frequency shift of the device were significantly improved. Overall, the mechanically engineered surface-based (nanorod) SAW gas sensor offered better sensing response than the layered SAW gas sensor in terms of sensitivity performance.

  9. Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ruby Ghosh; Reza Loloee; Roger Tobin

    2008-09-30

    A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device, Pt/SiO{sub 2}/SiC that can detect hydrogen-containing species in chemically reactive, high temperature (600 C) environments. We demonstrate that the device can be used as a hydrogen monitor in syngas applications of common interferants as well as sulfur and water vapor. These measurements were made in the Catalyst Screening Unit at NETL, Morgantown under atmospheric conditions. The sensor response to hydrogen gas at 350 C is 240 mV/decade, this is significantly higher than the device response to room temperature gas or that predicted from vacuum chamber studies. The enhanced catalytic activity of the platinum sensing film under energy plant operating conditions was investigated via AFM, x-ray diffraction, TEM and x-ray photoelectron spectroscopy. Our characterization indicated that exposure to high temperature gases significantly modifies the morphology of the Pt catalytic film and the Pt/SiO{sub 2} interfacial region, which we tentatively attribute to the enhanced hydrogen sensitivity of the sensing film. A model for the hydrogen/oxygen response of the SiC device under atmospheric conditions was developed. It is based on two independent phenomena: a chemically induced shift in the metal-semiconductor work function difference and the passivation/creation of charged states at the SiO{sub 2}-SiC interface. The optimum operating set point for the SiC sensor with respect to response time and long term reliability was determined to be close to mid-gap. Ultrahigh vacuum (UHV) techniques were used to investigate the effects of sulfur contamination on the Pt gate. Exposure to hydrogen sulfide, even in the presence of hydrogen or oxygen at partial pressures of 20-600 times greater than the H2S level, rapidly coated the gate with a monolayer of sulfur. Although

  10. Gas Phase Sensing of Alcohols by Metal Organic Framework–Polymer Composite Materials

    Science.gov (United States)

    2017-01-01

    Affinity layers play a crucial role in chemical sensors for the selective and sensitive detection of analytes. Here, we report the use of composite affinity layers containing Metal Organic Frameworks (MOFs) in a polymeric matrix for sensing purposes. Nanoparticles of NH2-MIL-53(Al) were dispersed in a Matrimid polymer matrix with different weight ratios (0–100 wt %) and drop-casted on planar capacitive transducer devices. These coated devices were electrically analyzed using impedance spectroscopy and investigated for their sensing properties toward the detection of a series of alcohols and water in the gas phase. The measurements indicated a reversible and reproducible response in all devices. Sensor devices containing 40 wt % NH2-MIL-53(Al) in Matrimid showed a maximum response for methanol and water. The sensor response time slowed down with increasing MOF concentration until 40 wt %. The half time of saturation response (τ0.5) increased by ∼1.75 times for the 40 wt % composition compared to devices coated with Matrimid only. This is attributed to polymer rigidification near the MOF/polymer interface. Higher MOF loadings (≥50 wt %) resulted in brittle coatings with a response similar to the 100 wt % MOF coating. Cross-sensitivity studies showed the ability to kinetically distinguish between the different alcohols with a faster response for methanol and water compared to ethanol and 2-propanol. The observed higher affinity of the pure Matrimid polymer toward methanol compared to water allows also for a higher uptake of methanol in the composite matrices. Also, as indicated by the sensing studies with a mixture of water and methanol, the methanol uptake is independent of the presence of water up to 6000 ppm of water. The NH2-MIL-53(Al) MOFs dispersed in the Matrimid matrix show a sensitive and reversible capacitive response, even in the presence of water. By tuning the precise compositions, the affinity kinetics and overall affinity can be tuned, showing

  11. Gas sensitivity and sensing mechanism studies on Au-doped TiO₂ nanotube arrays for detecting SF₆ decomposed components.

    Science.gov (United States)

    Zhang, Xiaoxing; Yu, Lei; Tie, Jing; Dong, Xingchen

    2014-10-17

    The analysis to SF6 decomposed component gases is an efficient diagnostic approach to detect the partial discharge in gas-insulated switchgear (GIS) for the purpose of accessing the operating state of power equipment. This paper applied the Au-doped TiO2 nanotube array sensor (Au-TiO2 NTAs) to detect SF6 decomposed components. The electrochemical constant potential method was adopted in the Au-TiO2 NTAs' fabrication, and a series of experiments were conducted to test the characteristic SF6 decomposed gases for a thorough investigation of sensing performances. The sensing characteristic curves of intrinsic and Au-doped TiO2 NTAs were compared to study the mechanism of the gas sensing response. The results indicated that the doped Au could change the TiO2 nanotube arrays' performances of gas sensing selectivity in SF6 decomposed components, as well as reducing the working temperature of TiO2 NTAs.

  12. Model Catalysis of Ammonia Synthesis ad Iron-Water Interfaces - ASum Frequency Generation Vibrational Spectroscopic Study of Solid-GasInterfaces and Anion Photoelectron Spectroscopic Study of Selected Anionclusters

    Energy Technology Data Exchange (ETDEWEB)

    Ferguson, Michael James [Univ. of California, Berkeley, CA (United States)

    2005-01-01

    The ammonia synthesis reaction has been studied using single crystal model catalysis combined with sum frequency generation (SFG) vibrational spectroscopy. The adsorption of gases N2, H2, O2 and NH3 that play a role in ammonia synthesis have been studied on the Fe(111) crystal surface by sum frequency generation vibrational spectroscopy using an integrated Ultra-High Vacuum (UHV)/high-pressure system. SFG spectra are presented for the dissociation intermediates, NH2 (~3325 cm-1) and NH (~3235 cm-1) under high pressure of ammonia or equilibrium concentrations of reactants and products on Fe(111) surfaces. Special attention was paid to understand how potassium promotion of the iron catalyst affects the intermediates of ammonia synthesis. An Fe(111) surface promoted with 0.2 monolayers of potassium red shifts the vibrational frequencies of the reactive surface intermediates, NH and NH2, providing evidence for weakened the nitrogen-hydrogen bonds relative to clean Fe(111). Spectral features of these surface intermediates persisted to higher temperatures for promoted iron surfaces than for clean Fe(111) surfaces implying that nitrogen-iron bonds are stronger for the promoted surface. The ratio of the NH to NH2 signal changed for promoted surfaces in the presence of equilibrium concentrations of reactants and products. The order of adding oxygen and potassium to promoted surfaces does not alter the spectra indicating that ammonia induces surface reconstruction of the catalyst to produce the same surface morphology. When oxygen is co-adsorbed with nitrogen, hydrogen, ammonia or potassium on Fe(111), a relative phase shift of the spectra occurs as compared to the presence of adsorbates on clean iron surfaces. Water adsorption on iron was also probed using SFG vibrational spectroscopy. For both H2O and D2O, the only spectral feature was in the range of

  13. Applications of a Mid-IR Quantum Cascade Laser in Gas Sensing Research

    KAUST Repository

    Sajid, Muhammad Bilal

    2015-05-01

    Laser absorption based sensors are extensively used in a variety of gas sensing areas such as combustion, atmospheric research, human breath analysis, and high resolution infrared spectroscopy. Quantum cascade lasers have recently emerged as high resolution, high power laser sources operating in mid infrared region and can have wide tunability range. These devices provide an opportunity to access stronger fundamental and combination vibrational bands located in mid infrared region than previously accessible weaker overtone vibrational bands located in near infrared region. Spectroscopic region near 8 µm contains strong vibrational bands of methane, acetylene, hydrogen peroxide, water vapor and nitrous oxide. These molecules have important applications in a wide range of applications. This thesis presents studies pertaining to spectroscopy and combustion applications. Advancements in combustion research are imperative to achieve lower emissions and higher efficiency in practical combustion devices such as gas turbines and engines. Accurate chemical kinetic models are critical to achieve predictive models which contain several thousand reactions and hundreds of species. These models need highly reliable experimental data for validation and improvements. Shock tubes are ideal devices to obtain such information. A shock tube is a homogenous, nearly constant volume, constant pressure, adiabatic and 0-D reactor. In combination with laser absorption sensors, shock tubes can be used to measure reaction rates and species time histories of several intermediates and products formed during pyrolysis and oxidation of fuels. This work describes measurement of the decomposition rate of hydrogen peroxide which is an important intermediate species controlling reactivity of combustion system in the intermediate temperature range. Spectroscopic parameters (linestrengths, broadening coefficients and temperature dependent coefficients) are determined for various transitions of

  14. Liquid petroleum gas sensing performance enhanced by CuO modification of nanocrystalline ZnO-TiO2

    Directory of Open Access Journals (Sweden)

    Pedhekar R.B.

    2016-09-01

    Full Text Available Nanocrystalline ZnO-TiO2 (with molar ratios 9:1, 7:3, 1:1, 3:7 and 1:9 were successfully synthesized by hydrothermal method. Synthesized materials were examined with the help of X-ray diffraction and transmission electron microscope. Liquid petroleum gas sensing characteristics of the ZnO-TiO2 films were investigated at different operating temperatures. The ZnO-TiO2 thick film (with 1:1 molar ratio exhibited good response toward liquid petroleum gas as compared to other investigated compositions. Further, liquid petroleum gas sensing characteristics of CuO modified ZnO-TiO2 thick films were investigated. 0.2 M CuO modified ZnO-TiO2 thick film exhibited excellent liquid petroleum gas sensing characteristics such as higher response (~ 1637.49 at 185 °C with quick response time (~30 s, low recovery time (~70 s, excellent repeatability and stability at low operating temperature.

  15. Flexible Transparent Films Based on Nanocomposite Networks of Polyaniline and Carbon Nanotubes for High-Performance Gas Sensing.

    Science.gov (United States)

    Wan, Pengbo; Wen, Xuemei; Sun, Chaozheng; Chandran, Bevita K; Zhang, Han; Sun, Xiaoming; Chen, Xiaodong

    2015-10-28

    A flexible, transparent, chemical gas sensor is assembled from a transparent conducting film of carbon nanotube (CNT) networks that are coated with hierarchically nanostructured polyaniline (PANI) nanorods. The nanocomposite film is synthesized by in-situ, chemical oxidative polymerization of aniline in a functional multiwalled CNT (FMWCNT) suspension and is simultaneously deposited onto a flexible polyethylene terephthalate (PET) substrate. An as-prepared flexible transparent chemical gas sensor exhibits excellent transparency of 85.0% at 550 nm using the PANI/FMWCNT nanocomposite film prepared over a reaction time of 8 h. The sensor also shows good flexibility, without any obvious decrease in performance after 500 bending/extending cycles, demonstrating high-performance, portable gas sensing at room temperature. This superior performance could be attributed to the improved electron transport and collection due to the CNTs, resulting in reliable and efficient sensing, as well as the high surface-to-volume ratio of the hierarchically nanostructured composites. The excellent transparency, improved sensing performance, and superior flexibility of the device, may enable the integration of this simple, low-cost, gas sensor into handheld flexible transparent electronic circuitry and optoelectronic devices.

  16. Ammonia and ammonium hydroxide sensors for ammonia/water absorption machines: Literature review and data compilation

    Science.gov (United States)

    Anheier, N. C., Jr.; McDonald, C. E.; Cuta, J. M.; Cuta, F. M.; Olsen, K. B.

    1995-05-01

    This report describes an evaluation of various sensing techniques for determining the ammonia concentration in the working fluid of ammonia/water absorption cycle systems. The purpose was to determine if any existing sensor technology or instrumentation could provide an accurate, reliable, and cost-effective continuous measure of ammonia concentration in water. The resulting information will be used for design optimization and cycle control in an ammonia-absorption heat pump. Pacific Northwest Laboratory (PNL) researchers evaluated each sensing technology against a set of general requirements characterizing the potential operating conditions within the absorption cycle. The criteria included the physical constraints for in situ operation, sensor characteristics, and sensor application. PNL performed an extensive literature search, which uncovered several promising sensing technologies that might be applicable to this problem. Sixty-two references were investigated, and 33 commercial vendors were identified as having ammonia sensors. The technologies for ammonia sensing are acoustic wave, refractive index, electrode, thermal, ion-selective field-effect transistor (ISFET), electrical conductivity, pH/colormetric, and optical absorption. Based on information acquired in the literature search, PNL recommends that follow-on activities focus on ISFET devices and a fiber optic evanescent sensor with a colormetric indicator. The ISFET and fiber optic evanescent sensor are inherently microminiature and capable of in situ measurements. Further, both techniques have been demonstrated selective to the ammonium ion (NH4(+)). The primary issue remaining is how to make the sensors sufficiently corrosion-resistant to be useful in practice.

  17. Ammonia and ammonium hydroxide sensors for ammonia/water absorption machines: Literature review and data compilation

    Energy Technology Data Exchange (ETDEWEB)

    Anheier, N.C. Jr.; McDonald, C.E.; Cuta, J.M.; Cuta, F.M.; Olsen, K.B.

    1995-05-01

    This report describes an evaluation of various sensing techniques for determining the ammonia concentration in the working fluid of ammonia/water absorption cycle systems. The purpose of this work was to determine if any existing sensor technology or instrumentation could provide an accurate, reliable, and cost-effective continuous measure of ammonia concentration in water. The resulting information will be used for design optimization and cycle control in an ammonia-absorption heat pump. PNL researchers evaluated each sensing technology against a set of general requirements characterizing the potential operating conditions within the absorption cycle. The criteria included the physical constraints for in situ operation, sensor characteristics, and sensor application. PNL performed an extensive literature search, which uncovered several promising sensing technologies that might be applicable to this problem. Sixty-two references were investigated, and 33 commercial vendors were identified as having ammonia sensors. The technologies for ammonia sensing are acoustic wave, refractive index, electrode, thermal, ion-selective field-effect transistor (ISFET), electrical conductivity, pH/colormetric, and optical absorption. Based on information acquired in the literature search, PNL recommends that follow-on activities focus on ISFET devices and a fiber optic evanescent sensor with a colormetric indicator. The ISFET and fiber optic evanescent sensor are inherently microminiature and capable of in situ measurements. Further, both techniques have been demonstrated selective to the ammonium ion (NH{sub 4}{sup +}). The primary issue remaining is how to make the sensors sufficiently corrosion-resistant to be useful in practice.

  18. Structural, morphological and gas sensing study of zinc doped tin oxide nanoparticles synthesized via hydrothermal technique

    Science.gov (United States)

    Singh, Davender; Kundu, Virender Singh; Maan, A. S.

    2016-07-01

    The pure and Zn-doped SnO2 nanoparticles were prepared successfully by hydrothermal route on large scale having different doping concentration of zinc from 0 to 0.20%. The calcined nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) for structural and morphological studies. XRD analyses reveal that the nanoparticles of these doping concentrations are polycrystalline in nature and existed as tetragonal rutile structure, SEM study of images confirms the existence of very small, homogeneously distributed, and spherical nanoparticles. The particles size of the nanoparticles was calculated by Scherrer formula and was found in the range of 9-21 nm. The presence of dopant (i.e. zinc) and formation of Sn-O phase and hydrous nature of Zn-doped SnO2 nanoparticles are confirmed by EDX and FTIR study. The gas sensing properties of pure and Zn-doped SnO2 nanoparticles were investigated for various concentrations of methanol, ethanol and acetone at different operating temperatures and it has been found that with doping concentration of zinc (x = 0.20%) shows the maximum response 78% to methanol, 65% to ethanol and 62% to acetone respectively at different operating temperature within the measurement limit for a concentration of 100 ppm of each gases.

  19. Synthesis of Ce-doped SnO2 nanoparticles and their acetone gas sensing properties

    Science.gov (United States)

    Lian, Xiaoxue; Li, Yan; Tong, Xiaoqiang; Zou, Yunling; Liu, Xiulin; An, Dongmin; Wang, Qiong

    2017-06-01

    Hydrothermal method was generally used to synthesis nanoparticles, which was used to fabricate pure and Ce-doped (3 wt%, 5 wt%, 7 wt%) SnO2 nanoparticles in this experiment. The as-prepared products were characterized by X-ray diffraction (XRD), energy dispersive spectrum (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET). The results clearly indicated that the nanoparticles were composed of SnO2 nanoparticles and Ce ions were successfully doped into the SnO2 lattice, and 5 wt% SnO2:Ce has a higher specific surface area (173.53 m2/g). Importantly, SnO2:Ce sensor had obviously improved performance compared to pure SnO2 and exhibited the highest response values (50.5 for 50 ppm) and a well selectivity to acetone at 270 °C. It could detect acetone gas in a wide concentration range with very high response, good long-term stability and repeatability of response. The possible sensing mechanism was discussed in this paper.

  20. A porous cadmium(II) framework. Synthesis, crystal structure, gas adsorption, and fluorescence sensing properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Pingping [College of Sciences, Agricultural University of Hebei, Baoding (China)

    2017-05-18

    The Cd{sup II} compound, namely [Cd(Tppa)(SO{sub 4})(H{sub 2}O)]{sub n} (1) [Tppa = tris(4-(pyridyl)phenyl) amine], was synthesized by the reaction of CdSO{sub 4}.8H{sub 2}O and Tppa under solvothermal conditions. Single crystal X-ray diffraction analysis revealed that compound 1 features a 3D porous framework based on 1D inorganic -[Cd-SO{sub 4}-Cd]{sub n}- chains. Topological analysis reveals that compound 1 represents a trinodal (3,4,6)-connected topological network with the point symbol of {6.7"2}{sub 2}{6"4.7.10}{6"4.7"5.8"4.10"2}. Gas adsorption properties investigations indicate that compound 1 exhibits moderate adsorption capacities for light hydrocarbons at room temperature. Luminescence property studies revealed that this Cd{sup II} compound exhibits high fluorescence sensitivity for sensing of CS{sub 2} molecule. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Synthesis and Gas-sensing Performance of Nanosized SnO2

    Institute of Scientific and Technical Information of China (English)

    WANG Shu-rong; WU Shi-hua; SHI Juan; ZHENG Xiu-cheng

    2005-01-01

    Nanosized tin dioxide particles were prepared by sol-gel dialytic processes with tin(Ⅳ) chloride and alcohol as start materials. The nanoparticles of tin dioxide were charactered by thermogravimetry and differential thermal analysis(TG-DTA), X-ray diffraction(XRD), transmission electron microscopy (TEM) and BET. The results show that the average diameter of tin dioxide particles dried at 353 K was about 2 nm. Even if the tin dioxide particles were calcined at 873 K, the average diameter of particles was less than 10 nm. The removal of Cl- was solved by using this kind of method. The mechanism of the formation of tin dioxide nanosized particles was proposed and analyzed in this paper. We also measured the sensitivity of the sensor based on the tin oxide powder calcined at 673 K to NH3, alcohol, acetone, hexane and CO. The gas-sensing performance results indicate that this sensor has a higher sensitivity to alcohol and acetone, and selectivity for NH3, hexane and CO at an operating temperature of 343 K.

  2. ZnO nanotube array: Gas sensing properties at room temperature

    Science.gov (United States)

    Dadhich, B.; Ganapathi, S. Kailasa; Priyam, A.; Kaur, Manmeet; Debnath, A. K.; Muthe, K. P.; Gadkari, S. C.

    2017-05-01

    In the present study, ZnO nanotube arrays were synthesized from hydrothermally grown ZnO nanowires by selective chemical etching, using KCl as dissolving solution. Synthesized ZnO nanotube arrays were characterized using X-ray diffraction, scanning electron microscopy, UV-visible and Raman spectroscopy. Room temperature gas sensing properties of these arrays were investigated towards various toxic gases and the results were compared to that of ZnO nanowire arrays. Samples of ZnO nano tube arrays showed better sensor response to both H2S (4.2 for 5 ppm) and NO2 (13 for 1.5 ppm) as compared to samples of ZnO nanowires array which exhibited a sensor response of 3.7 towards 5 ppm H2S and 1 towards 1.5 ppm NO2. The enhancement of sensor response in nanotube arrays can be attributed to the hollow morphology of the ZnO NT which offers higher surface area. Oxygen adsorption in this case takes place on both inner and outer surfaces of the tube resulting in larger change in resistance.

  3. Quantum dots as mediators in gas sensing: A case study of CdS sensitized WO{sub 3} sensing composites

    Energy Technology Data Exchange (ETDEWEB)

    Concina, Isabella, E-mail: concina@sensor.ing.unibs.it [CNR-INO SENSOR Laboratory, via Branze, 45, 25131 Brescia (Italy); SENSOR, Department of Information Engineering, Brescia University, via Valotti, 9, 25133 Brescia (Italy); Comini, Elisabetta [CNR-INO SENSOR Laboratory, via Branze, 45, 25131 Brescia (Italy); SENSOR, Department of Information Engineering, Brescia University, via Valotti, 9, 25133 Brescia (Italy); Kaciulis, Saulius [CNR-ISMN, Institute for the Study of Nanostructured Materials, Via dei Taurini, 19, 00185 Roma (Italy); Sberveglieri, Giorgio [CNR-INO SENSOR Laboratory, via Branze, 45, 25131 Brescia (Italy); SENSOR, Department of Information Engineering, Brescia University, via Valotti, 9, 25133 Brescia (Italy)

    2014-01-30

    In this study the proof of principle of the use of naked semiconductor directly generated on metal oxide surface as mediators in gas sensing is provided. Successive ionic layer absorption and reaction (SILAR) technique has been applied to sensitize a WO{sub 3} thin film with CdS quantum dots. Response to gases of bare WO{sub 3} is deeply modified: quantum dots dramatically increase the metal oxide conductance, otherwise rather poor, and modify the capability of detecting environmental pollutants, such as CO and NO{sub 2}. A modified sensing mechanism is proposed to rationalize the mediation exerted by the semiconducting active layer on the interaction between gaseous species and WO{sub 3} surface.

  4. Equilibrium and kinetic studies of in situ generation of ammonia from urea in a batch reactor for flue gas conditioning of thermal power plants

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, J.N.; Patwardhan, A.V.; Meikap, B.C. [Indian Institute of Technology, Kharagpur (India). Dept. of Chemical Engineering

    2009-03-15

    Ammonia has long been known to be useful in the treatment of flue/tail/stack gases from industrial furnaces, incinerators, and electric power generation industries. In this study, urea hydrolysis for production of ammonia, in different application areas that require safe use of ammonia at in situ condition, was investigated in a batch reactor. The equilibrium and kinetic study of urea hydrolysis was done in a batch reactor at reaction pressure to investigate the effect of reaction temperature, initial feed concentration, and time on ammonia production. This study reveals that conversion increases exponentially with an increase in temperature but with increases in initial feed concentration of urea the conversion decreases marginally. Further, the effect of time on conversion has also been studied; it was found that conversion increases with increase in time. Using collision theory, the temperature dependency of forward rate constant developed from which activation energy of the reaction and the frequency factor has been calculated. The activation energy and frequency factor of urea hydrolysis reaction at atmospheric pressure was found to be 73.6 kJ/mol and 2.89 x 10{sup 7} min{sup -1}, respectively.

  5. Performance of silica-supported copper oxide sorbents for SO@#x@#/NO@#x@#-removal from flue gas II. Selective catalytic reduction of nitric oxide by ammonia

    NARCIS (Netherlands)

    Kiel, J.H.A.; Kiel, J.H.A.; Edelaar, A.C.S.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

    1992-01-01

    The selective catalytic reduction (SCR) of nitric oxide by ammonia was studied for silica-supported copper oxide particles to be used as a sorbent/catalyst in a continuous process for the simultaneous removal of SOx and NOx from flue gases. The SCR-behaviour was determined as a function of the

  6. Study of Room Temperature H2S Gas Sensing Behavior of CuO-modified BSST Thick Film Resistors

    Directory of Open Access Journals (Sweden)

    H. M. Baviskar

    2008-05-01

    Full Text Available Thick films of (Ba0.1Sr0.9(Sn0.5Ti0.5O3 referred as BSST, were prepared by screen-printing technique. The preparation, characterization and gas sensing properties of pure and CuO-BSST mixed oxide semiconductors have been investigated. The mixed oxides were obtained by dipping the pure BSST thick films into 0.01 M aqueous solution of CuCl2, for different intervals of time. Pure BSST was observed to be less sensitive to H2S gas. However, mixed oxides of CuO and BSST were observed to be highly sensitive to H2S gas. Upon exposure to H2S gas, the barrier height of CuO-BSST intergranular regions decreases markedly due to the chemical transformation of CuO into well conducting CuS leading to a drastic decrease in resistance. The crucial gas response was found to H2S gas at room temperature and no cross sensitivity was observed to other hazardous and polluting gases. The effects of microstructure and doping concentration on the gas response, selectivity, response and recovery of the sensor in the presence of H2S gas were studied and discussed.

  7. Notched Long-Period Fiber Grating with an Amine-Modified Surface Nanostructure for Carbon Dioxide Gas Sensing

    Directory of Open Access Journals (Sweden)

    Janw-Wei Wu

    2015-07-01

    Full Text Available This paper presents the fabrication and application of a notched long-period fiber grating (NLPFG with an amine-modified surface nanostructure for carbon dioxide (CO2 gas sensing. The NLPFG with the modified surface nanostructure was fabricated by using inductively coupled plasma (ICP etching with an Ag nanoparticle etching barrier. The experimental results show that the spectra were changed with the CO2 gas flow within 12 min. Thereafter, the spectra of the NLPFG remained steady and unchanged. During the absorption process, the transmission loss was decreased by approximately 2.019 dB, and the decreased rate of transmission loss was 0.163 dB/min. The sensitivity was about −0.089 dB/%. These results demonstrate that the NLPFG CO2 gas sensor has the advantages of steady performance, repeatability, and low cost. Therefore, the NLPFG can be utilized as a reliable CO2 gas sensor.

  8. Gas sensing and conductivity relationship on nanoporous thin films: A CaCu{sub 3}Ti{sub 4}O{sub 12} case study

    Energy Technology Data Exchange (ETDEWEB)

    Felix, A.A., E-mail: aafelixy@yahoo.com.br; Longo, E.; Varela, J.A.; Orlandi, M.O.

    2016-04-01

    In this work, CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) thin films were synthesized with the polymeric precursor method and characterized by structural (X-ray diffraction) and morphological (scanning electron microscopy) techniques. These films were composed of a single CCTO phase and presented high surface porosity. The gas sensing response and conductivity-type relationship were investigated by two different approaches. Gas sensing measurements performed at different temperatures using different atmospheres showed that the CCTO has n-type gas sensing behavior and can detect small amounts of oxidizing gases with high sensitivity and selectivity. The type of intrinsic conductivity was also investigated through thermopower measurements, which indicated intrinsic n-type conductivity in CCTO thin films prepared with the polymeric precursor method and confirmed the direct relationship between the gas sensing behavior and the intrinsic conductivity of CCTO. - Highlights: • Nanoporous gas sensing CaCu{sub 3}Ti{sub 4}O{sub 12} thin films • CaCu{sub 3}Ti{sub 4}O{sub 12} thin films are prepared with the polymeric precursor method • Films exhibited n-type gas sensing behavior and high sensitivity to oxidizing gases. • Gas sensing and conductivity relationship is established.

  9. All-soft, battery-free, and wireless chemical sensing platform based on liquid metal for liquid- and gas-phase VOC detection.

    Science.gov (United States)

    Kim, Min-Gu; Alrowais, Hommood; Kim, Choongsoon; Yeon, Pyungwoo; Ghovanloo, Maysam; Brand, Oliver

    2017-06-27

    Lightweight, flexible, stretchable, and wireless sensing platforms have gained significant attention for personal healthcare and environmental monitoring applications. This paper introduces an all-soft (flexible and stretchable), battery-free, and wireless chemical microsystem using gallium-based liquid metal (eutectic gallium-indium alloy, EGaIn) and poly(dimethylsiloxane) (PDMS), fabricated using an advanced liquid metal thin-line patterning technique based on soft lithography. Considering its flexible, stretchable, and lightweight characteristics, the proposed sensing platform is well suited for wearable sensing applications either on the skin or on clothing. Using the microfluidic sensing platform, detection of liquid-phase and gas-phase volatile organic compounds (VOC) is demonstrated using the same design, which gives an opportunity to have the sensor operate under different working conditions and environments. In the case of liquid-phase chemical sensing, the wireless sensing performance and microfluidic capacitance tunability for different dielectric liquids are evaluated using analytical, numerical, and experimental approaches. In the case of gas-phase chemical sensing, PDMS is used both as a substrate and a sensing material. The gas sensing performance is evaluated and compared to a silicon-based, solid-state gas sensor with a PDMS sensing film.

  10. Transformation of ammonia i biological airfilters

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter; Sørensen, Karen; Andersen, Mathias

    2007-01-01

    nitrite oxidation only appeared in locations with minimal ammonia and nitrite levels. Nitrous oxide emission depended on anoxic microsites, and nitric oxide production was associated with nitrite accumulation. Water and biomass management appear to be the important tools for optimization of ammonia......Ammonia is a major compound in ventilation air from animal houses. In biological filters it is with varying efficiency transformed by physical, biological, and chemical processes and ends up as ammonium, nitrate, and nitrite dissolved in water and as dinitrogen, nitrous oxide and nitric oxide...... removal without too much energy consumption, waste water production, green house gas emission, or suppression of the filters odor removal efficiency....

  11. Ammonia toxicity in fish.

    Science.gov (United States)

    Randall, D J; Tsui, T K N

    2002-01-01

    Ammonia is present in the aquatic environment due to agricultural run-off and decomposition of biological waste. Ammonia is toxic to all vertebrates causing convulsions, coma and death, probably because elevated NH4+ displaces K+ and depolarizes neurons, causing activation of NMDA type glutamate receptor, which leads to an influx of excessive Ca2+ and subsequent cell death in the central nervous system. Present ammonia criteria for aquatic systems are based on toxicity tests carried out on, starved, resting, non-stressed fish. This is doubly inappropriate. During exhaustive exercise and stress, fish increase ammonia production and are more sensitive to external ammonia. Present criteria do not protect swimming fish. Fish have strategies to protect them from the ammonia pulse following feeding, and this also protects them from increases in external ammonia, as a result starved fish are more sensitive to external ammonia than fed fish. There are a number of fish species that can tolerate high environmental ammonia. Glutamine formation is an important ammonia detoxification strategy in the brain of fish, especially after feeding. Detoxification of ammonia to urea has also been observed in elasmobranches and some teleosts. Reduction in the rate of proteolysis and the rate of amino acid catabolism, which results in a decrease in ammonia production, may be another strategy to reduce ammonia toxicity. The weather loach volatilizes NH3, and the mudskipper, P. schlosseri, utilizes yet another unique strategy, it actively pumps NH4+ out of the body.

  12. Band parameters for self-broadened ammonia gas in the range 0.74 to 5.24 μm to support measurements of the atmosphere of the planet Jupiter

    Science.gov (United States)

    Bowles, Neil; Calcutt, Simon; Irwin, Pat; Temple, Jon

    2008-08-01

    We present new measurements and modelling of low-resolution transmission spectra of self-broadened ammonia gas, one of the most important absorbers found in the near-infrared spectrum of the planet Jupiter. These new spectral measurements were specifically designed to support measurements of Jupiter's atmosphere made by the Near-Infrared Mapping Spectrometer (NIMS) which was part of the Galileo mission that orbited Jupiter from 1995 to September 2003. To reach approximate jovian conditions in the lab, a new gas spectroscopy facility was developed and used to measure self-broadened ammonia spectra from 0.74 to 5.2 μm, virtually the complete range of the NIMS instrument, for the first time. Spectra were recorded at temperatures varying from 300 to 215 K, pressures from 1000 to 33 mb and using three different path lengths (10.164, 6.164 and 2.164 m). The spectra were then modelled using a series of increasingly complex physically based transmittance functions.

  13. Summary of Technology of Recovery and Utilization of Carbon Dioxide from Ammonia Tail Gas%合成氨尾气中二氧化碳回收利用技术总结

    Institute of Scientific and Technical Information of China (English)

    王洪玲; 晁承龙; 陈允梅

    2011-01-01

    A presentation is given of the recovery and utilization of carbon dioxide from ammonia tail gas, technological norms, main pieces of equipment, and special technological characteristics of the unit. This recovery unit uses the tail gas from the ammonia production process as its feedstock, adopts the patent technology of adsorption-rectification, and yields food-grade and technical carbon dioxide products which conform to the national standard, with food-grade product at 90 kt/a and a purity of at ≥99.95% ( volume fraction), and technical product at 210 kt/a and a purity of ≥99.80% ( volume fraction).%介绍了合成氨尾气中二氧化碳回收利用的情况及流程、技术指标、主要设备、装置的技术特点.该二氧化碳回收装置以合成氨生产过程中排放的尾气为原料,采用吸附精馏专利技术,生产出符合国家标准的食品级和工业级二氧化碳产品;食品级产品产量90 kt/a,纯度≥99.95%(体积分数);工业级产品产量210 kt/a,纯度≥99.80%(体积分数).

  14. Greenhouse gas source identification and flux measurements using an optical remote sensing method and a photoacoustic multi-gas analyzer

    Science.gov (United States)

    Soil properties such as particle size, soil organic carbon (SOC) and moisture contents, tillage operations and crop management practices influence greenhouse gas emission or consumption patterns from agricultural lands. Greenhouse gas (GG) emissions have been measured on small field plots, although ...

  15. Ammonia measurement with a pH electrode in the ammonia/urea-SCR process

    Science.gov (United States)

    Kröcher, Oliver; Elsener, Martin

    2007-03-01

    The selective catalytic reduction of nitrogen oxides with ammonia (ammonia SCR) and urea (urea SCR), respectively, is a widespread process to clean flue and diesel exhaust gases due to its simplicity and efficiency. The main challenge of the process is to minimize the ammonia emissions downstream of the SCR catalyst. We found that ammonia emissions of >10 ppm can reliably be detected with a simple pH electrode in the presence of CO2, SOx, NOx, and moderately weak organic acids. 10-20 ppm of ammonia in the exhaust gas are sufficient to neutralize the acids and to increase the pH value from 3 to 6. On this basis a continuous measuring method for ammonia was developed, which was used to control the dosage of urea in the SCR process. While keeping the ammonia emissions after the SCR catalyst at 5-30 ppm an average NOx removal efficiency (DeNOx) of >95% were achieved at a diesel test rig. The method can also be applied for exhaust gases with higher acid contents, if a basic pre-filter is added adsorbing the acidic exhaust components. Compared to water as absorption solution, more precise ammonia measurements are possible, if a 0.1 M NH4Cl absorption solution is applied, whose pH value is changing as a Nernst function of the ammonia concentration.

  16. MEASUREMENT OF AMMONIA EMISSIONS FROM MECHANICALLY VENTILATED POULTRY HOUSES USING MULTIPATH TUNABLE DIODE LASER SPECTROSCOPY

    Science.gov (United States)

    Ammonia emissions from mechanically ventilated poultry operations are an important environmental concern. Open Path Tunable Diode Laser Absorption Spectroscopy has emerged as a robust real-time method for gas phase measurement of ammonia concentrations in agricultural settings. ...

  17. Synthesis, characterization and enhanced gas sensing performance of porous ZnCo2O4 nano/microspheres.

    Science.gov (United States)

    Liu, Tie; Liu, Jingyuan; Liu, Qi; Song, Dalei; Zhang, Hongseng; Zhang, Hongquan; Wang, Jun

    2015-12-14

    In recent years, spinel-type compounds have attracted great interest because of their gem-like qualities. However, little is known of their gas sensing properties. We report, in this paper, on a self-assembly method to prepare porous ZnCo2O4 (ZCO) nano/microspheres by a facile one-step solvothermal process and subsequent annealing. Abundant techniques were used to characterize the morphology and structure of the as-obtained compounds. Our data indicate that the hierarchical nano/microspheres are constructed from numerous nanoparticles primarily, which have a higher specific surface area (ca. 77.3 m(2) g(-1)) and are of uniform diameter (ca. 1 μm). To demonstrate their potential application, gas sensors based on the as-synthesized ZCO nano/microspheres were fabricated to test their sensing performance, whose sensing behaviours correspond to p-type semiconductors. The test results also indicate that porous spinel-type compounds have an excellent kinetic response to ethanol at an operating temperature of 175 °C and a superior selectivity. As such, hierarchical porous ZnCo2O4 nano/microspheres will hold promising potential in the gas sensor field.

  18. Physical synthesis methodology and enhanced gas sensing and photoelectrochemical performance of 1D serrated zinc oxide-zinc ferrite nanocomposites.

    Science.gov (United States)

    Liang, Yuan-Chang; Liu, Shang-Luen; Hsia, Hao-Yuan

    2015-12-01

    We successfully prepared one-dimensional ZnO-ZnFe2O4 (ZFO) heterostructures for acetone gas-sensing and photoelectrochemical applications, by using sputter deposition of ZFO crystallites on ZnO nanostructure templates. The nanoscale ZFO crystallites were homogeneously coated on the surfaces of the ZnO nanostructures. Electron microscope images revealed that the ZnO-ZFO heterostructures exhibited a serrated surface morphology. Coating the ZnO nanostructures with a ZFO aggregated layer appreciably enhanced their acetone gas-sensing capability at 250 °C in comparison with pure ZnO nanostructures. The presence of many depleted nanoscale ZFO crystallites, the rugged surface of the heterostructures, and electron depletion at the ZnO/ZFO interface might contribute to the enhanced acetone gas-sensing response. Furthermore, the larger surface area and higher light absorption of ZnO-ZFO relative to the surface area and light absorption of ZnO were correlated with a substantial enhancement of the photocurrent value of ZnO-ZFO in photoelectrochemical tests produced by the simulated solar light irradiation.

  19. cGAS Senses Human Cytomegalovirus and Induces Type I Interferon Responses in Human Monocyte-Derived Cells

    Science.gov (United States)

    Paijo, Jennifer; Döring, Marius; Spanier, Julia; Grabski, Elena; Nooruzzaman, Mohammed; Schmidt, Tobias; Witte, Gregor; Messerle, Martin; Hornung, Veit; Kaever, Volkhard; Kalinke, Ulrich

    2016-01-01

    Human cytomegalovirus (HCMV) infections of healthy individuals are mostly unnoticed and result in viral latency. However, HCMV can also cause devastating disease, e.g., upon reactivation in immunocompromised patients. Yet, little is known about human immune cell sensing of DNA-encoded HCMV. Recent studies indicated that during viral infection the cyclic GMP/AMP synthase (cGAS) senses cytosolic DNA and catalyzes formation of the cyclic di-nucleotide cGAMP, which triggers stimulator of interferon genes (STING) and thus induces antiviral type I interferon (IFN-I) responses. We found that plasmacytoid dendritic cells (pDC) as well as monocyte-derived DC and macrophages constitutively expressed cGAS and STING. HCMV infection further induced cGAS, whereas STING expression was only moderately affected. Although pDC expressed particularly high levels of cGAS, and the cGAS/STING axis was functional down-stream of STING, as indicated by IFN-I induction upon synthetic cGAMP treatment, pDC were not susceptible to HCMV infection and mounted IFN-I responses in a TLR9-dependent manner. Conversely, HCMV infected monocyte-derived cells synthesized abundant cGAMP levels that preceded IFN-I production and that correlated with the extent of infection. CRISPR/Cas9- or siRNA-mediated cGAS ablation in monocytic THP-1 cells and primary monocyte-derived cells, respectively, impeded induction of IFN-I responses following HCMV infection. Thus, cGAS is a key sensor of HCMV for IFN-I induction in primary human monocyte-derived DC and macrophages. PMID:27058035

  20. One-dimensional photonic crystals for eliminating cross-talk in mid-IR photonics-based respiratory gas sensing

    Science.gov (United States)

    Fleming, L.; Gibson, D.; Song, S.; Hutson, D.; Reid, S.; MacGregor, C.; Clark, C.

    2017-02-01

    Mid-IR carbon dioxide (CO2) gas sensing is critical for monitoring in respiratory care, and is finding increasing importance in surgical anaesthetics where nitrous oxide (N2O) induced cross-talk is a major obstacle to accurate CO2 monitoring. In this work, a novel, solid state mid-IR photonics based CO2 gas sensor is described, and the role that 1- dimensional photonic crystals, often referred to as multilayer thin film optical coatings [1], play in boosting the sensor's capability of gas discrimination is discussed. Filter performance in isolating CO2 IR absorption is tested on an optical filter test bed and a theoretical gas sensor model is developed, with the inclusion of a modelled multilayer optical filter to analyse the efficacy of optical filtering on eliminating N2O induced cross-talk for this particular gas sensor architecture. Future possible in-house optical filter fabrication techniques are discussed. As the actual gas sensor configuration is small, it would be challenging to manufacture a filter of the correct size; dismantling the sensor and mounting a new filter for different optical coating designs each time would prove to be laborious. For this reason, an optical filter testbed set-up is described and, using a commercial optical filter, it is demonstrated that cross-talk can be considerably reduced; cross-talk is minimal even for very high concentrations of N2O, which are unlikely to be encountered in exhaled surgical anaesthetic patient breath profiles. A completely new and versatile system for breath emulation is described and the capability it has for producing realistic human exhaled CO2 vs. time waveforms is shown. The cross-talk inducing effect that N2O has on realistic emulated CO2 vs. time waveforms as measured using the NDIR gas sensing technique is demonstrated and the effect that optical filtering will have on said cross-talk is discussed.