Design Guidelines for High Sensitivity ZnO Nanowire Gas Sensors With Schottky Contact

A SiC Schottky dual-diode temperature-sensing element, suitable for both complementary variation of VF with absolute temperature (CTAT) and differential proportional to absolute temperature (PTAT) sensors, is demonstrated over 60–700 K, currently the widest range reported. The structure’s layout places the two identical diodes in close, symmetrical proximity. A stable and high-barrier Schottky contact based on Ni, annealed at 750 °C, is used. XRD analysis evinced the even distribution of Ni2Si over the entire Schottky contact area. Forward measurements in the 60–700 K range indicate nearly identical characteristics for the dual-diodes, with only minor inhomogeneity. Our parallel diode (p-diode) model is used to parameterize experimental curves and evaluate sensing performances over this far-reaching domain. High sensitivity, upwards of 2.32 mV/K, is obtained, with satisfactory linearity (R2 reaching 99.80%) for the CTAT sensor, even down to 60 K. The PTAT differential version boasts increased linearity, up to 99.95%. The lower sensitivity is, in this case, compensated by using a high-performing, low-cost readout circuit, leading to a peak 14.91 mV/K, without influencing linearity.

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Direct Production of a Novel Iron-Based Nanocomposite from the Laser Pyrolysis ofFe(CO)5/MMAMixtures: Structural and Sensing Properties

Journal of Nanomaterials ◽

10.1155/2010/324532 ◽

2010 ◽

Vol 2010 ◽

pp. 1-12 ◽

Cited By ~ 4

Author(s):

R. Alexandrescu ◽

I. Morjan ◽

A. Tomescu ◽

C. E. Simion ◽

M. Scarisoreanu ◽

...

Keyword(s):

Iron Oxide ◽

Gas Sensors ◽

High Sensitivity ◽

X Ray Diffraction ◽

Direct Production ◽

X Ray ◽

Metallic Particles ◽

Ir Laser ◽

Iron Iron ◽

Optimum Working

Iron/iron oxide-based nanocomposites were prepared by IR laser sensitized pyrolysis ofFe(CO)5and methyl methacrylate (MMA) mixtures. The morphology of nanopowder analyzed by TEM indicated that mainly core-shell structures were obtained. X-ray diffraction techniques evidence the cores as formed mainly by iron/iron oxide crystalline phases. A partially degraded (carbonized) polymeric matrix is suggested for the coverage of the metallic particles. The nanocomposite structure at the variation of the laser density and of the MMA flow was studied. The new materials prepared as thick films were tested for their potential for acting as gas sensors. The temporal variation of the electrical resistance in presence ofNO2, CO, andCO2, in dry and humid air was recorded. Preliminary results show that the samples obtained at higher laser power density exhibit rather high sensitivity towardsNO2detection andNO2selectivity relatively to CO andCO2. An optimum working temperature of200°Cwas found.

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Comparison of Online Sensors for Liquid Phase Hydrogen Sulphide Monitoring in Sewer Systems

Water ◽

10.3390/w13131876 ◽

2021 ◽

Vol 13 (13) ◽

pp. 1876

Author(s):

Daneish Despot ◽

Micaela Pacheco Fernández ◽

Matthias Barjenbruch

Keyword(s):

Liquid Phase ◽

Gas Sensors ◽

High Sensitivity ◽

Laboratory Method ◽

Control Measures ◽

Monitoring And Control ◽

Sewer Systems ◽

H2s Emission ◽

H2s Detection ◽

Online Sensors

Hydrogen sulfide (H2S) related to wastewater in sewer systems is known for causing significant problems of corrosion and odor nuisance. Sewer systems severely affected by H2S typically rely on online H2S gas sensors for monitoring and control. However, these H2S gas sensors only provide information about the H2S emission potential at the point being monitored, which is sometimes inadequate to design control measures. In this study, a comparison of three market-ready online sensors capable of liquid-phase H2S detection in sewer systems was assessed and compared. Two of the three sensors are based on UV/Vis spectrophotometry, while the other adapted the design and principles of a Clark-type electrochemical microsensor. The H2S measurements of the sensors were statistically compared to a standard laboratory method at first. Following that, the performance of the online sensors was evaluated under realistic sewer conditions using the Berlin Water Company (BWB) research sewer pilot plant. Test applications representing scenarios of typical H2S concentrations found in sulfide-affected sewers and during control measures were simulated. The UV/Vis spectrometers showed that the performance of the sensors was highly dependent on the calibration type and measurements used for deriving the calibration function. The electrochemical sensor showed high sensitivity by responding to alternating anaerobic/anoxic conditions simulated during nitrate dosing. All sensors were prone to measurement disturbances due to high amounts of sanitary solids in wastewater at the study site and required continuous maintenance for reliable measurements. Finally, a summary of the key attributes and limitations of the sensors compared for liquid phase H2S detection is outlined.

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Influence of Large Relative Tip Clearances for a Micro Radial Fan and Design Guidelines for Increased Efficiency

Volume 8: Industrial and Cogeneration; Manufacturing Materials and Metallurgy; Marine; Microturbines, Turbochargers, and Small Turbomachines ◽

10.1115/gt2020-15994 ◽

2020 ◽

Author(s):

Patrick H. Wagner ◽

Jan Van herle ◽

Lili Gu ◽

Jürg Schiffmann

Keyword(s):

Pressure Rise ◽

Leading Edge ◽

High Sensitivity ◽

Design Guidelines ◽

Tip Clearance ◽

Small Scale ◽

Blade Tip ◽

Dynamics Simulations ◽

Experimental Findings ◽

Blade Tip Clearance

Abstract The blade tip clearance loss was studied experimentally and numerically for a micro radial fan with a tip diameter of 19.2mm. Its relative blade tip clearance, i.e., the clearance divided by the blade height of 1.82 mm, was adjusted with different shims. The fan characteristics were experimentally determined for an operation at the nominal rotational speed of 168 krpm with hot air (200 °C). The total-to-total pressure rise and efficiency increased from 49 mbar to 68 mbar and from 53% to 64%, respectively, by reducing the relative tip clearance from 7.7% to the design value of 2.2%. Single and full passage computational fluid dynamics simulations correlate well with these experimental findings. The widely-used Pfleiderer loss correlation with an empirical coefficient of 2.8 fits the numerical simulation and the experiments within +2 efficiency points. The high sensitivity to the tip clearance loss is a result of the design specific speed of 0.80, the highly-backward curved blades (17°), and possibly the low Reynolds number (1 × 105). The authors suggest three main measures to mitigate the blade tip clearance losses for small-scale fans: (1) utilization of high-precision surfaced-grooved gas-bearings to lower the blade tip clearance, (2) a mid-loaded blade design, and (3) an unloaded fan leading edge to reduce the blade tip clearance vortex in the fan passage.

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Doubly resonant sub-ppt photoacoustic gas detection with eight decades dynamic range

10.21203/rs.3.rs-431688/v1 ◽

2021 ◽

Author(s):

Zhen Wang ◽

Hui Zhang ◽

Qiang Wang ◽

Simone Borri ◽

Iacopo Galli ◽

...

Keyword(s):

Gas Sensors ◽

Near Infrared ◽

Dynamic Range ◽

High Sensitivity ◽

Fast Response ◽

Wide Dynamic Range ◽

Acoustic Resonators ◽

Light Waves ◽

Energy Environment ◽

Small Footprint

Abstract Gas sensors with high sensitivity, wide dynamic range, high selectivity, fast response, and small footprint are desirable across a broad range of applications in energy, environment, safety, and public health. However, designing a compact gas sensor with ultra-high sensitivity and ultra-wide dynamic range remains a challenge. Laser-based photoacoustic spectroscopy (PAS) is a promising candidate to fill this gap. Herein, we report a novel method to simultaneously enhance the acoustic and light waves for PAS using integrated optical and acoustic resonators. This increases sensitivity by more than two orders of magnitude and extends the dynamic range by more than three orders of magnitude, compared with the state-of-the-art photoacoustic gas sensors. We demonstrate the concept by exploiting a near-infrared absorption line of acetylene (C2H2) at 1531.59 nm, achieving a detection limit of 0.5 parts-per-trillion (ppt), a noise equivalent absorption (NEA) of 5.7×10-13 cm-1 and a linear dynamic range of eight orders of magnitude. This study enables the realization of compact ultra-sensitive and ultra-wide-dynamic-range gas sensors in a number of different fields.

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