CH4 Gas Sensor Research Articles

Ni2O3 decoration of In2O3 nanostructures for catalytically enhanced methane sensing

The explosive limit of methane (CH4) gas concentration is 5%. However, detection of CH4 gas at lower concentrations is essential for prevention and warning purposes in leaking gas systems. In this study, a simple method for fabricating thin films of granular indium oxide (In2O3) particles decorated with nickel oxide (Ni2O3) nanoparticles was developed for high response CH4 gas sensor. The In2O3 granular film was fabricated by sputter deposition of indium, followed by oxidation. Ni2O3 nanoparticles were deposited onto the In2O3 film by arc-discharge deposition of single-wall carbon nanotubes (SWCNTs) with Ni catalyst nanowires, followed by burning the carbon nanotubes. The Ni nanoparticle catalysts deposited on the SWCNTs were then oxidized to Ni2O3.The Ni2O3 nanoparticles on the surface exhibited a catalytic role in methane gas reactions, resulting in reduction of operation temperature. The sensors showed relatively high response percentage per 100 ppm methane gas concentration.

A 1.65 μm three-section distributed Bragg reflector (DBR) laser for CH4 gas sensors

A 1.65-μm three-section distributed Bragg reflector (DBR) laser for CH4 gas sensors is reported. The DBR laser has a wide tunable range covering the R3 and R4 methane absorption line manifolds. The wavelength tunability properties, temperature stability and laser linewidth are characterized and analyzed. Several advantages were demonstrated compared with traditional DFB lasers in harmonic detection.

Temperature compensated NDIR CH4 gas sensor with focused beam structure

With concave mirror surfaces, the IR light has been focused into circular shape and the intensity of IR light on the detector side has been enhanced effectively. Based upon the simulation results, a new NDIR gas sensor has been prototyped with high efficiency. Using concave mirror surfaces, the output voltages of gas sensor are significantly increased about from 2.15 V (vertical mirror structure) to 3.62 V at 0 ppm CH4 concentration. After temperature compensation, the detection error has been reduced from 2000 ppm to less than 200 ppm within 15 °C to 35 °C.

Sn/In/Ti nanocomposite sensor for CH4 detection

Abstract Novel CH4 gas sensors made of the nanocomposites of Sn/In/Ti oxides were investigated. The nanosized crystalline oxides and their composites were successfully prepared by a sol–gel and controlled precipitation method, respectively, through manipulating the salts concentration, precipitation pH value, aging time and composition of composites. The derived precursors exhibited superior thermal stability. To ensure sufficient crystallinity and insignificant grain growth of the materials, the appropriate calcination temperatures were 600 °C for 4 h and 700 °C for 2 h for the precursors of oxides and composites, respectively. The performance and structure of the composites were characterized by EDX, TEM, BET, TG–DTA and XRD. The sensing tests showed that these nanocomposites exhibited high response and selectivity for the detection of CH4 at operating temperatures between 200 °C and 250 °C and the response depended on the composition of composites, calcination temperature, operating temperature and gas concentration in air. The gas sensing mechanism of the sensors was also discussed by X-ray photoelectron spectroscopic (XPS) and temperature-programmed desorption (TPD) studies.

$\hbox {CH}_{4}$ Sensor of Sn, In, and Ti Nanosized Oxides

A novel CH4 gas sensor based on the nanocomposites and mixed oxides of Sn, In, and Ti, workable at near room temperature, were developed. The binary and ternary oxides were prepared by a chemical controlled step precipitation method and mixed route. The preparation parameters-salt concentration, cation ratio, precipitation pH, and aging time-have been optimized, and their optimal value were 0.05 M, 20% Ti: 20% In: 60% Sn, pH=8.0 and aged 24 h, respectively. The appropriate calcinations temperature for precursor and mixture were 600 degC 4 h and 700 degC 2 h. The performance and structure of the materials were characterized by TEM, BET, TG-DTA, XRD, TPD, and XPS. The sensing tests showed that these nanomaterials exhibited high sensitivity and selectivity for CH4 and their sensing properties depended on the oxide composition, calcinations temperature, operating temperature, and gas concentration. The gas-sensing mechanism of the sensor was also discussed by TPD and XPS analysis

The influence of melt purification and structure defects on mid-infrared light emitting diodes

Mid-infrared light emitting diodes which exhibit more than 7 mW (pulsed) and 0.35 mW dc output power at 3.3 μm and at room temperature have been fabricated by liquid phase epitaxy using Pb as a neutral solvent. Using Pb solution an increase in pulsed output power of between two and three times was obtained compared with InAs light emitting diodes (LEDs) made using rare-earth gettering. The performance improvements were attributed to a reduction in residual carrier concentration arising from the removal of un-intentional donors and structure defects in the InAs active region material. These LEDs are well matched to the CH4 absorption spectrum and potentially could form the basis of a practical infrared CH4 gas sensor.

Powerful interface light emitting diodes for methane gas detection

Powerful (light emitting diodes) LEDs which exhibit more than 3.5 mW of output power at room temperature have been fabricated by liquid phase epitaxy (LPE) and characterized. These LEDs are well matched to the CH4 absorption spectrum and confirm the potential of the devices as a key component for use in an infrared CH4 gas sensor. We report on the efficient interface electroluminescence in our LEDs across the InAs/InAsSbP heterojunction consistent with type II emission. This directly suppresses the Auger recombination and enables these sources to emit maximum powers in excess of 3 mW at room temperature. Furthermore, the use of Yb rare earth ion gettering in these devices was found to be effective in increasing the LED output power. We attribute this to a reduction in the residual carrier concentration arising from the removal of unintentional donors and point defects in the InAs active region material. The ring contact geometry was also found to be superior when compared to the dot contacts in our structures. The LEDs demonstrated in this work are sufficiently powerful to be used in a practical methane gas sensor.

LPE growth and characterization of InGaAsP/InP heterostructures: IR light-emitting diodes at 1.66 μm. Application to the remote monitoring of methane gas

Highly effective IR light-emitting diodes operating at the wavelength 1.66 μm and based on the buried heterostructure In 0.88Ga 0.12As 0.26P 0.74/ In 0.72Ga 0.28As 0.62P 0.38/In 0.53Ga 0.47As/InP have been grown by liquid-phase epitaxy (LPE) and characterized in detail by means of transmission electron microscopy (TEM), high-resolution electron microscopy (HREM), electron diffraction (ED), X-ray diffraction (XRD), secondaryion mass spectrometry (SIMS) and electroluminescence measurements, The InGaAsP epilayers are found to be well lattice matched and of good structural quality. A tentative explanation is presented for the spinodal decomposition observed in InGaAsP alloys. A new type of selective CH4 gas sensor has been developed and fabricated on the basis of the IR light-emitting diode mentioned above. Especially designed for the remote control of CH 4 gas via fibre optics, an integrated optoelectronic readout scheme has been developed and tested. It is shown that the proposed type of sensor can be used for the quantitative remote control of CH 4 gas concentration (0.2-100%) via a fibre glass line up to a distance of 2 × 1 km.

Thick-film Gas Sensor for City Gas

SnO2-based CH4 gas sensors have been developed by using a thick-film technology. Thickfilm gas sensors have been prepared by the mixture of the silica sol such as hydrophilic silica, hydrophobic silica, or methanol silica and the SnO2-based powders with 1 wt% PdCl2 and 0.5wt% MgO. The dependence of the sensitivity and the mechanical strength of these sensors on the concentration of silica were investigated. It is found that the thick-film sensor with methanol silica has high sensitivity to CH4 gas as well as excellent mechanical strength. From the results of these experiments, the effects of hydroxyl groups adsorbed on the, surface of sensors on the sensitivity have been discussed.