scholarly journals Testing the Reliability of Flexible MOX Gas Sensors under Strain

Proceedings ◽  
2019 ◽  
Vol 14 (1) ◽  
pp. 20
Author(s):  
M. Alvarado ◽  
A. Romero ◽  
J.L. Ramírez ◽  
S. De la Flor ◽  
E. Llobet
Keyword(s):  
Gas Sensors ◽  
Tungsten Trioxide ◽  
Sensor Response ◽  
Bending Test ◽  
Before And After

We present flexible chemo-resistive sensors based on AACVD grown tungsten trioxide (WO3) nanowires. The sensor response to gases, before and after a 50-cycle bending test, is reported. Thus, proving that reliable gas sensors, able to withstand repeated bending, have been achieved. Moreover, their integrity and durability have been tested under harsh bending conditions until break down.

Crystalline structure, defects and gas sensor response to NO2 and H2S of tungsten trioxide nanopowders

2003 ◽  
Vol 93 (1-3) ◽  
pp. 475-485 ◽  
Author(s):  
I. Jiménez ◽  
J. Arbiol ◽  
G. Dezanneau ◽  
A. Cornet ◽  
J.R. Morante
Keyword(s):  
Gas Sensor ◽  
Crystalline Structure ◽  
Tungsten Trioxide ◽  
Sensor Response ◽  
Structure Defects

scholarly journals Short-Time Fourier Transform and Decision Tree-Based Pattern Recognition for Gas Identification Using Temperature Modulated Microhotplate Gas Sensors

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Aixiang He ◽  
Jun Yu ◽  
Guangfen Wei ◽  
Yi Chen ◽  
Hao Wu ◽  
...  
Keyword(s):  
Pattern Recognition ◽  
Fourier Transform ◽  
Decision Tree ◽  
Gas Sensors ◽  
Operating Temperature ◽  
Ambient Air ◽  
Sensor Response ◽  
Short Time Fourier Transform ◽  
Short Time ◽  
Different Gases

Because the sensor response is dependent on its operating temperature, modulated temperature operation is usually applied in gas sensors for the identification of different gases. In this paper, the modulated operating temperature of microhotplate gas sensors combined with a feature extraction method based on Short-Time Fourier Transform (STFT) is introduced. Because the gas concentration in the ambient air usually has high fluctuation, STFT is applied to extract transient features from time-frequency domain, and the relationship between the STFT spectrum and sensor response is further explored. Because of the low thermal time constant, the sufficient discriminatory information of different gases is preserved in the envelope of the response curve. Feature information tends to be contained in the lower frequencies, but not at higher frequencies. Therefore, features are extracted from the STFT amplitude values at the frequencies ranging from 0 Hz to the fundamental frequency to accomplish the identification task. These lower frequency features are extracted and further processed by decision tree-based pattern recognition. The proposed method shows high classification capability by the analysis of different concentration of carbon monoxide, methane, and ethanol.

scholarly journals Performance of Flexible Chemoresistive Gas Sensors after Having Undergone Automated Bending Tests

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5190 ◽  
Author(s):  
Miriam Alvarado ◽  
Silvia De La Flor ◽  
Eduard Llobet ◽  
Alfonso Romero ◽  
José Luis Ramírez
Keyword(s):  
Metal Oxide ◽  
Gas Sensing ◽  
Flexible Substrate ◽  
Test Procedure ◽  
Chemical Vapor ◽  
Bending Test ◽  
Bending Tests ◽  
Ag Electrodes ◽  
Different Types ◽  
Before And After

Many sensors are developed over flexible substrates to be used as wearables, which does not guarantee that they will actually withstand being bent. This work evaluates the gas sensing performance of metal oxide devices of three different types, before and after having undergone automated, repetitive bending tests. These tests were aimed at demonstrating that the fabricated sensors were actually flexible, which cannot be taken for granted beforehand. The active layer in these sensors consisted of WO3 nanowires (NWs) grown directly over a Kapton foil by means of the aerosol-assisted chemical vapor deposition. Their response to different H2 concentrations was measured at first. Then, they were cyclically bent, and finally, their response to H2 was measured again. Sensors based on pristine WO3-NWs over Ag electrodes and on Pd-decorated NWs over Au electrodes maintained their performance after having been bent. Ag electrodes covered with Pd-decorated NWs became fragile and lost their usefulness. To summarize, two different types of truly flexible metal oxide gas sensor were fabricated, whereas a third one was not flexible, despite being grown over a flexible substrate following the same method. Finally, we recommend that one standard bending test procedure should be established to clearly determine the flexibility of a sensor considering its intended application.

Synthesis, Structural and Gas Sensing Characterization of W-Doped SnO2 Nanostructures

2017 ◽  
Vol 381 ◽  
pp. 15-19 ◽  
Author(s):  
Mukesh Chander Bhatnagar ◽  
Anima Johari
Keyword(s):  
Low Temperature ◽  
Gas Sensors ◽  
Gas Sensing ◽  
Operating Temperature ◽  
Environmental Pollutants ◽  
Sensor Response ◽  
Gas Content ◽  
Temperature Sensitive ◽  
Oxide Material ◽  
Industry Waste

Tin oxide material has been extensively used for gas sensing application. Due to high operating temperature of metal oxide gas sensors, around 600 K and long term instability, research has been carried out to improve the material properties and reducing operating temperature. nanostructure materials have shown higher sensitivity and better stability towards gas environment. Air pollutants from automobiles and industry waste are the primary sources of environmental pollutants and there is need to develop low temperature, sensitive and selective gas sensors to monitor the gas content. In this paper, we have discussed the effect of Tungsten (W) doping in SnO2 nanostructures on the structural and gas sensing properties. The nanostructures have been synthesized by thermal evaporation process. The structural and surface morphology studies confirm the growth of nanowires on silicon substrates. The corresponding EDX spectra also confirm the doping of W into SnO2 nanowires. The gas sensor response of W-doped SnO2 nanowires was investigated upon exposure to various gases. It has been observed that doping of W enhances the NO2 sensitivity of nanowire based sensors at low temperature and the sensor response improves with increase in gas concentration.

BAs nanotubes with non-circular cross section shapes for gas sensors

2020 ◽  
Vol 22 (22) ◽  
pp. 12584-12590
Author(s):  
Xinyue Dai ◽  
Yanyan Jiang ◽  
Hui Li
Keyword(s):  
Transport Properties ◽  
Cross Section ◽  
Gas Sensors ◽  
Electronic Transport ◽  
Circular Cross Section ◽  
Electronic Transport Properties ◽  
Before And After

Electronic transport properties of circular and elliptical BAs nanotubes before and after encapsulation of water.

scholarly journals Application of Low-Cost Electrochemical Sensors to Aqueous Systems to Allow Automated Determination of NH3 and H2S in Water

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2814
Author(s):  
Malcolm Cämmerer ◽  
Thomas Mayer ◽  
Stefanie Penzel ◽  
Mathias Rudolph ◽  
Helko Borsdorf
Keyword(s):  
Mathematical Model ◽  
Gas Sensors ◽  
Water Samples ◽  
Electrochemical Sensors ◽  
Low Cost ◽  
Sensor Response ◽  
Measured Signal ◽  
Gas Streams ◽  
Air Stream ◽  
Low Humidity

Usage of commercially available electrochemical gas sensors is currently limited by both the working range of the sensor with respect to temperature and humidity and the spikes in sensor response caused by sudden changes in temperature or humidity. Using a thermostatically controlled chamber, the sensor response of ammonia and hydrogen sulfide sensors was studied under extreme, rapidly changing levels of humidity with the aim of analyzing nebulized water samples. To protect the sensors from damage, the gas stream was alternated between a saturated gas stream from a Flow Blurring® nebulizer and a dry air stream. When switching between high and low humidity gas streams, the expected current spike was observed and mathematically described. Using this mathematical model, the signal response due to the change in humidity could be subtracted from the measured signal and the sensor response to the target molecule recorded. As the sensor response is determined by the model while the sensor is acclimatizing to the new humid conditions, a result is calculated faster than that by systems that rely on stable humidity. The use of the proposed mathematical model thus widens the scope of electrochemical gas sensors to include saturated gas streams, for example, from nebulized water samples, and gas streams with variable humidity.

scholarly journals Thin Film Gas Sensors Based on Planetary Ball-Milled Zinc Oxide Nanoinks: Effect of Milling Parameters on Sensing Performance

2021 ◽  
Vol 11 (20) ◽  
pp. 9676
Author(s):  
Raju Sapkota ◽  
Pengjun Duan ◽  
Tanay Kumar ◽  
Anusha Venkataraman ◽  
Chris Papadopoulos
Keyword(s):  
Thin Film ◽  
Zinc Oxide ◽  
Gas Sensors ◽  
Zno Nanoparticles ◽  
Food Packaging ◽  
Room Temperature ◽  
Industrial Applications ◽  
Sensor Response ◽  
Particle Sizes ◽  
Zno Nanoparticle

Planetary ball-milled zinc oxide (ZnO) nanoparticle suspensions (nanoinks) were used to produce thin film chemiresistive gas sensors that operate at room temperature. By varying milling or grinding parameters (speed, time, and solvent) different thin film gas sensors with tunable particle sizes and porosity were fabricated and tested with dry air/oxygen against hydrogen, argon, and methane target species, in addition to relative humidity, under ambient light conditions. Grinding speeds of up to 1000 rpm produced particle sizes and RMS thin film roughness below 100 nm, as measured by atomic force and scanning electron microscopy. Raman spectroscopy, photoluminescence, and X-ray analysis confirmed the purity and structure of the resulting ZnO nanoparticles. Gas sensor response at room temperature was found to peak for nanoinks milled at 400 rpm and for 30 min in ethylene glycol and deionized water, which could be correlated to an increased film porosity and enhanced variation in electron concentration resulting from adsorption/desorption of oxygen ions on the surfaces of ZnO nanoparticles. Sensor response and dynamic behavior was found to improve as the temperature was increased, peaking between 100 and 150 °C. This work demonstrates the use of low-cost PBM nanoinks as the active materials for solution-processed thin film gas/humidity sensors for use in environmental, medical, food packaging, laboratory, and industrial applications.

Analysis of the Effect of Cyclic Fatigue on the Flexural Strength of a Ceramoceramic System Used in Dental Prostheses

2018 ◽  
Vol 930 ◽  
pp. 43-47
Author(s):  
Cristiane Fonseca de Carvalho ◽  
Cláudio Luis de Melo-Silva ◽  
Tereza Cristina Favieri de Melo-Silva ◽  
Fábio Amaral de Araújo ◽  
Jefferson Fabricio Cardoso Lins
Keyword(s):  
Flexural Strength ◽  
Ceramic Coating ◽  
Cyclic Fatigue ◽  
Bending Test ◽  
Mean Values ◽  
Three Point Bending ◽  
Cyclic Stresses ◽  
Dental Prostheses ◽  
Before And After ◽  
The Mean

The aim of this study was to analyze the flexural strength of ceramics based on yttria-stabilized zirconia (YTZP) , used in the manufacture of dental prostheses infrastructure before and after aging with cyclic fatigue in moisture. The samples were made by pre-sintered blocks of ZirkonTransluzent (Zirkonzahn GMHB) from YTZP ceramics with and without feldspathic ceramic coating, divided into groups: G1 = YTZP control; G2 = YTZP aged; G3 = YTZP + feldspathic; G4 = YTZP + aged feldspathic. The samples were submitted to a three-point bending test with a speed of 0.5 mm / min. The mean values of the flexural strength values were G1 = 645 MPa (DP ± 124), G2 = 681 MPa (DP ± 129), G3 = 904Mpa (DP ± 157) and G4 = 954Mpa (DP ± 243). The values of groups G1 and G2; G3 and G4 were statistically similar, depending on the presence or absence of coating. Cyclic stresses did not affect the flexural strength of the material

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