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CH <sub/>4</sub> Concentration Distribution in a Semiconductor Process Chamber Measured by the CT-TDLAS
摘要： We measured methane (CH4) concentration distribution in a semiconductor process chamber by using the computed tomography-tunable diode laser spectroscopy (CT-TDLAS). We designed the CT-TDLAS measurement system with a 32-laser-path. The CH4 concentration distribution was measured by the CT-TDLAS based on the 32 absorption spectra which were collected by scanning the laser wavelength around the CH4 absorption peak of 1653.7 nm. We checked linearity of the measurement, validity of the algorithm, and resolution of the computed tomography (CT) reconstructed distribution. In the algorithm check, we measured a simple concentration distribution generated in a ?ve-fold concentric cylinder. Next, we designed a semiconductor process chamber in which the 32-laser-path was installed. After quantitative evaluations of the CT reconstructed distributions by comparing the simulated results of computational ?uid dynamics, we actually measured the CH4 concentration distribution in the chamber when we streamed 10% CH4 from one of four inlet ports and nitrogen from other three ports into the chamber. The measured distributions were obviously different in accordance with the CH4 inlet location, although all the inlet ports were located cyclic-symmetrically. Those results indicated that the ?ow impedances of the four exhaust holes on the susceptor were different depending their locations.
关键词： computed tomography,semiconductor process chamber,CT-TDLAS,methane concentration distribution,tunable diode laser spectroscopy
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Methane Detection in the Longwave Infrared
摘要： Monitoring and mapping atmospheric methane is becoming increasingly important due to its role as a greenhouse gas and the fact its atmospheric concentration has been rising in recent years. Many remote sensing techniques exist to detect the presence of methane in the atmosphere including active sensing with lidar systems, passive sensing in the solar reflective spectral region, and passive sensing in the longwave thermal infrared. This study examined the temperature contrast in the longwave infrared of an enhanced concentration of methane in a near surface plume for a variety of concentrations, plume temperatures, and plume thicknesses. Results indicate radiometric temperature absolute differences for a narrow band (50 – 200 nm) centered on the 7.68 μm methane feature ranged from 0.0 to 6.8 K for the conditions studied. Future work will further validate and expand on these results.
关键词： modeling,multispectral imaging,longwave infrared,green house gas monitoring,methane
更新于2025-09-10 09:29:36
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Assessing the capability of different satellite observing configurations to resolve the distribution of methane emissions at kilometer scales
摘要： Anthropogenic methane emissions originate from a large number of fine-scale and often transient point sources. Satellite observations of atmospheric methane columns are an attractive approach for monitoring these emissions but have limitations from instrument precision, pixel resolution, and measurement frequency. Dense observations will soon be available in both low Earth and geostationary orbits, but the extent to which they can provide fine-scale information on methane sources has yet to be explored. Here we present an observation system simulation experiment (OSSE) to assess the capabilities of different satellite observing system configurations. We conduct a 1-week WRF-STILT simulation to generate methane column footprints at 1.3×1.3 km2 spatial resolution and hourly temporal resolution over a 290×235 km2 domain in the Barnett Shale in Northeast Texas, a major oil/gas field with a large number of point sources. We sub-sample these footprints to match the observing characteristics of the recently launched TROPOMI instrument (7×7 km2 pixels, 11 ppb precision, daily frequency), the planned GeoCARB instrument (2.7×3.0 km2 pixels, 4 ppb precision, nominal twice-daily frequency), and other proposed observing configurations. The information content of the various observing systems is evaluated using the Fisher information matrix and its eigenvalues. We find that a week of TROPOMI observations should effectively provide regional (～100 km) information on temporally invariant emissions but is very limited at finer scales. GeoCARB should provide 4-37% of the total information available for temporally invariant emissions in the Barnett Shale (～100 pieces of information). Improvements to the instrument precision yield greater increases in information content, compared to improved sampling frequency. A precision better than 6 ppb is an important threshold for achieving fine resolution of emissions. Transient emissions would be missed with either TROPOMI or GeoCARB. An aspirational high-resolution geostationary instrument with 1.3×1.3 km2 pixel resolution, hourly return time, and 1 ppb precision would effectively constrain the temporally invariant emissions in the Barnett Shale at the kilometer scale and provide some information on transient sources.
关键词： Fisher information matrix,GeoCARB,methane emissions,TROPOMI,satellite observations,WRF-STILT simulation
更新于2025-09-10 09:29:36
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Effect of hydrogen concentration on graphene synthesis using microwave-driven plasma-mediated methane cracking
摘要： Gas phase graphene forms as an aerosol in a microwave plasma among other carbon forms. Consisting of 2-6 sheets per stack with dimensions between 100 – 500 nm, it is referred to as nanographene (NG). Surprisingly, increasing H/C ratio in the feedstock increases the relative graphitic content of the product. Dependence of the different carbon forms upon H/C ratio of the gas feed mixture is shown across multiple analytical characterizations. Attributes of (a) phase quality (pristine nature of NG) and (b) phase quantity (how much NG forms relative to other carbon sp2 phases) are addressed. Phase identification of the forms is performed via transmission electron microscopy with quantification by thermogravimetric analysis, assessing their respective oxidative reactivity benchmarked to commercially available similar carbon products applied as standards. X-ray diffraction differentiates these forms based on varied extent of graphitic structure. Electron energy loss spectroscopy assesses graphitic content by the ratio of sp2/sp3 bonding. Raman spectroscopy supports the observed shift in relative proportions of the carbon forms towards preferential graphitic content with increasing H/C. Selected area diffraction illustrates this for NG. Fringe analyses of nanostructure quantifies this shift for carbon particles. Infra-red spectroscopy reveals complementary C-H bonding as a measure of graphitic quality.
关键词： electron energy loss spectroscopy,thermogravimetric analysis,hydrogen concentration,methane cracking,graphene synthesis,X-ray diffraction,nanographene,microwave-driven plasma,Raman spectroscopy,infra-red spectroscopy
更新于2025-09-10 09:29:36
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AIP Conference Proceedings [Author(s) 6TH INTERNATIONAL CONFERENCE ON PRODUCTION, ENERGY AND RELIABILITY 2018: World Engineering Science & Technology Congress (ESTCON) - Kuala Lumpur, Malaysia (13–14 August 2018)] - Electrical and optical properties of graphene oxide modified by nitrogen and methane plasma
摘要： The current-voltage (I-V) characteristic and photoresponse of partially reduced graphene oxide (rGO) treated with nitrogen and methane plasmas have been studied. Measurements of I-V characteristics showed that the illumination (incandescent lamp) of samples after plasma exposure leads to the appearance of a bend in the initially linear characteristic. The di?erence in the value of the currents with the illumination turned on and o? was up to 100 μA at a voltage of ±10 V. The relaxation time of the process is about 1 s. The observed e?ect depends on the plasma processing conditions, as well as on the thickness of the ?lms. The largest values of the photoresponse was observed at thicknesses of GO ?lms from 20 nm to 60-80 nm.
关键词： methane plasma,graphene oxide,nitrogen plasma,photoresponse,current-voltage characteristics
更新于2025-09-09 09:28:46
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FLAME PROPAGATION AND BURNING RATES OF METHANE-AIR MIXTURES USING SCHLIEREN PHOTOGRAPHY
摘要： Different methodology have been shown to produce different results for Markstein length and laminar burning velocity of methane-air mixture. This study attempts to determine the aforesaid parameters using the newly developed closed vessel combustion chamber with Schlieren photography. Markstein length and burning rate of methane-air mixture was determined under the initial pressure of 1 atm, temperature range of 298-302K and equivalence ratio range of 0.7-1.3. Experiments were performed in a centrally ignited 29.16L cylindrical constant volume combustion chamber. Ignition energy was set at 25mJ for each experiment. The images of spherically expanding flame were recorded using Schlieren photography technique at a speed of 2000 frame per second. Analysis of the flame area yield flame radii from which the flame speed and stretch rate could be obtained. These parameters would allow the determination of Markstein length and burning rate of the flame. Results show that Markstein length magnitude increases proportionally with equivalence ratio with a magnitude ranging from 0.125cm to 0.245cm. Maximum burning rate occurs at equivalence ratio of 1.1 with a magnitude of 0.366 m/s. Flame of each equivalence ratio also exhibits fluctuation arising from acoustic disturbance. This disturbance becomes more apparent at higher equivalence ratio.
关键词： Schlieren,closed vessel,Methane-air,burning rate,Markstein length
更新于2025-09-09 09:28:46
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Analysis and Design of an Effective Light Interference Methane Sensor Based on Three-Dimensional Optical Path Model
摘要： As an important environmental monitoring equipment, the existing methane sensors or the traditional interferometer-based methane detectors have some drawbacks, such as low accuracy, large size, and complex calibration operations. Moreover, the optical path model and analysis method for the light interference methane sensor are not practical. In this paper, an effective light interference methane sensor is proposed based on a three-dimensional optical path model with point light source. Based on this model, the interference optical system is studied to illustrate the cause of the interference fringes. Furthermore, the influencing factors of the light intensity distribution are analyzed and an adjustment method for the interference fringes is proposed, which helps to simplify the assembling and calibrating operations. In order to improve the measurement accuracy, a temperature drift compensation method which includes a mapping table, a steady-state compensator, and a dynamic compensator is proposed. The mapping table is established between the output voltages of photoelectric detector, and the methane concentration, the steady-state compensator, and the dynamic compensator are proposed to eliminate the temperature drift. Finally, an experimental device for the light interference methane sensor is constructed to validate the interference fringe adjustment method and the temperature drift compensation method.
关键词： temperature drift compensation,light interference,methane sensor,three-dimensional optical path model,interference fringes
更新于2025-09-09 09:28:46
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Green Energy based Thermochemical and Photochemical Hydrogen Production
摘要： A significant amount of hydrogen is required to satisfy the hydroprocessing needs of petroleum refinery, natural gas cleaning, and biofuel upgrading. Meanwhile, hydrogen is a very promising candidate of energy due to its high energy output per mass unit as compared to other sources of energy. In this article, the production of hydrogen is overviewed from the traditional technology as the thermochemical processes of fossil fuels to the current development in photoelectrochemical processes or even hybrid technologies. The catalysts for methane reforming and visible-light absorption were summarized. Both processes employ oxides as the catalyst. Because catalytic oxides are mostly lack of visible-light absorption function, the visible-light absorption properties could be rendered by doping these oxides with metal, nitrogen, or even sulfur. Further complete substitution of the oxygen atoms leads to non-oxide catalyst. Moreover, multidimensional photochemical catalysts have acquired more attention over traditional powered catalysts. Finally, a vision is exhibited for the efficiency and the future trends on production of H2.
关键词： Tri-reforming,catalyst,Biomass,Electrolysis,Dry Reforming,Hydrogen Production,Steam Reforming,Methane,Autothermal Reforming,Solar energy,Gasification,Coal
更新于2025-09-09 09:28:46
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Characterization of flame front propagation during early and late combustion for methane-hydrogen fueling of an optically accessible SI engine
摘要： In recent years, hybrid and fully electric vehicles have received significant consideration since they represent an alternative sustainable transport to the conventional fossil-fuel powered vehicles. However, a worldwide implementation of this alternative propulsion can induce large and undesirable peak demands in distributed power systems. In this context, natural gas spark ignition engines are a promising form of technology to supply part of the energy demand. The main limitations related to low laminar flame propagation speed and poor lean-burn capabilities of natural gas can be overcome by using hydrogen as additional fuel. In this paper, a comparison was carried out between methane and different CH4/H2 mixtures. Specifically, low levels of hydrogen addition were used (5%, 10%, 20% volumetric basis) in stoichiometric and lean burn conditions. The measurements were carried out in an optically accessible single-cylinder port fuel injection spark ignition engine. Optical measurements were performed to analyze the combustion process with high spatial and temporal resolution. In particular, optical techniques based on 2D-digital imaging with two different combustion chamber views were used. Macroscopic (global) and microscopic (local) post-processing tools were implemented to provide a detailed analysis of the flame front propagation process. Moreover, an in-depth analysis was performed to study the flame penetration in the piston top-land crevice. Exhaust gas emissions were also characterized and linked with thermodynamic and optical data. In order to evaluate the combustion process in similar fluid-dynamic conditions, all measurements were performed under steady-state conditions at fixed engine speed, load and spark advance. All the results highlight fast combustion promotion due to the hydrogen addition. In addition, hydrogen reduces the preferential propagation of the flame in a certain direction and increases the flame front wrinkling. Flame propagation in the top-land crevice region was measured for methane and its blends with hydrogen, which represents an original contribution to the literature. An inverse trend was seen between flame penetration in the crevice and unburned hydrocarbon emissions. Lastly, tests in lean conditions demonstrate the potential to decrease nitrogen oxides emissions when methane and methane-hydrogen blends are used.
关键词： Methane,SI engines,Crevice,Optical analysis,Hydrogen
更新于2025-09-09 09:28:46
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Visible-Light-Driven Conversion of CO2 to CH4 with an Organic Sensitizer and an Iron Porphyrin Catalyst
摘要： Using a phenoxazine-based organic photosensitizer and an iron porphyrin molecular catalyst, we demonstrated photochemical reduction of CO2 to CO and CH4 with turnover numbers (TONs) of 149 and 29, respectively, under visible light irradiation (λ > 435 nm) with a tertiary amine as sacrificial electron donor. This work is the first example of a molecular system using an earth-abundant metal catalyst and an organic dye to effect complete 8e-/8H+ reduction of CO2 to CH4, as opposed to typical 2e-/2H+ products of CO or formic acid. The catalytic system continuously produced methane even after prolonged irradiation up to four days. Using CO as the feedstock, the same reactive system was able to produce CH4 with 85% selectivity, 80 TON and a quantum yield of 0.47%. The redox properties of the organic photosensitizer and acidity of the proton source were shown to play a key role in driving the 8e-/8H+ processes.
关键词： methane,organic photosensitizer,CO2 reduction,iron porphyrin,visible light
更新于2025-09-09 09:28:46