Among various gas sensing materials, metal oxide semiconductors have shown great potential as resistive type sensors. The ordered porous structural metal oxide semiconductors with well-defined meso- or macro-pores che...Among various gas sensing materials, metal oxide semiconductors have shown great potential as resistive type sensors. The ordered porous structural metal oxide semiconductors with well-defined meso- or macro-pores chemically synthesized via soft-templating method and nanocasting strategy have high porosity, highly interconnected pore channels and high surface area with enormous active sites for interacting with gaseous molecules. These features enable them good performance in gas sensing, including high sensitivity, fast response and recovery, good selectivity. This review gives a comprehensive summary about the porous metal oxides with focus on the synthesis methods, structure related properties, as well as the modification strategies for gas sensing improved performances.展开更多
Three full-scale wastewater treatment processes, Orbal oxidation ditch, anoxic/anaerobic/aerobic （reversed A^2O） and anaerobic/anoxic/aerobic （A^2O）, were selected to investigate the emission characteristics of gr...Three full-scale wastewater treatment processes, Orbal oxidation ditch, anoxic/anaerobic/aerobic （reversed A^2O） and anaerobic/anoxic/aerobic （A^2O）, were selected to investigate the emission characteristics of greenhouse gases （GHG）, including carbon dioxide （CO2）, methane （CH4） and nitrous oxide （N2O）. Results showed that although the processes were different, the units presenting high GHG emission fluxes were remarkably similar, namely the highest CO2 and N2O emission fluxes occurred in the aerobic areas, and the highest CH4 emission fluxes occurred in the grit tanks. The GHG emission amount of each unit can be calculated from its area and GHG emission flux. The calculation results revealed that the maximum emission amounts of CO2, CH4 and N2O in the three wastewater treatment processes appeared in the aerobic areas in all cases. Theoretically, CH4 should be produced in anaerobic conditions, rather than aerobic conditions. However, results in this study showed that the CH4 emission fluxes in the forepart of the aerobic area were distinctly higher than in the anaerobic area. The situation for N2O was similar to that of CH4： the N2O emission flux in the aerobic area was also higher than that in the anoxic area. Through analysis of the GHG mass balance, it was found that the flow of dissolved GHG in the wastewater treatment processes and aerators may be the main reason for this phenomenon. Based on the monitoring and calculation results, GHG emission factors for the three wastewater treatment processes were determined. The A^2O process had the highest CO2 emission factor of 319.3 g CO2/kg CODremoved, and the highest CH4 and N2O emission factors of 3.3 g CH4/kg CODremoved and 3.6 g N2O/kg TNremoved were observed in the Orbal oxidation ditch process.展开更多
A systematic study of the two-dimensional electron gas at La AlO_3/SrTiO_3（110） interface reveals an anisotropy along two specific directions, [001] and 1ī0. The anisotropy becomes distinct for the interface prepar...A systematic study of the two-dimensional electron gas at La AlO_3/SrTiO_3（110） interface reveals an anisotropy along two specific directions, [001] and 1ī0. The anisotropy becomes distinct for the interface prepared under high oxygen pressure with low carrier density. Angular dependence of magnetoresistance shows that the electron confinement is stronger along the 1ī0 direction. Gate-tunable magnetoresistance reveals a clear in-plane anisotropy of the spin–orbit coupling,and the spin relaxation mechanism along both directions belongs to D＇yakonov–Perel＇（DP） scenario. Moreover, in-plane anisotropic superconductivity is observed for the sample with high carrier density, the superconducting transition temperature is lower but the upper critical field is higher along the 1ī0 direction. This in-plane anisotropy could be ascribed to the anisotropic band structure along the two crystallographic directions.展开更多
Most aquatic ecosystems contribute elevated N2 O to atmosphere due to increasing anthropogenic nitrogen loading. To further understand the spatial heterogeneity along an aquatic continuum from the upriver to wetland t...Most aquatic ecosystems contribute elevated N2 O to atmosphere due to increasing anthropogenic nitrogen loading. To further understand the spatial heterogeneity along an aquatic continuum from the upriver to wetland to lake to downriver, the study was conducted on spatial variations in N2 O emission along Poyang Lake aquatic continuum during the flood season from 15 July 2013 to 10 August 2013. The results showed the N2 O concentrations, the ratio of N2O/dinitrogen（N2） gases production, N2 O emission and denitrification rates ranged from 0.10 to 1.11 μg N/L,- 0.007% to 0.051%,- 9.73 to 127 μg N/m2/hr and 1.33 × 104to31.9 × 104μg N2/m2/hr, respectively, across the continuum. The average N2 O concentrations,the ratio of N2O/N2 and N2O emission was significantly lower in wetlands as compared to the rivers and lake（p 〈 0.01）. The significantly high denitrification rate and low N2 O emission together highlighted that most N2 O can be converted into N2 via near complete denitrification in the Poyang Lake wetlands. Our study suggests that the wetlands might impact N2 O budget in an integrated aquatic ecosystems. Moreover, N2 O emission from different aquatic ecosystem should be considered separately when quantifying the regional budget in aquatic ecosystem.展开更多
Surface water methane （CH4） and nitrous oxide （N20） concentrations and fluxes were investigated in two subtropical coastal embayments （Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Aus...Surface water methane （CH4） and nitrous oxide （N20） concentrations and fluxes were investigated in two subtropical coastal embayments （Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia）. Measurements were done at 23 stations in seven campaigns covering different seasons during 2010-2012. Water-air fluxes were estimated using the Thin Boundary Layer approach with a combination of wind and currents-based models for the estimation of the gas transfer velocities. The two bays were strong sources of both CH4 and N2O with no significant differences in the degree of saturation of both gases between them during all measurement campaigns. Both CH4 and N2O concentrations had strong temporal but minimal spatial variability in both bays. During the seven seasons, CH4 varied between 500% and 4000% saturation while N2O varied between 128 and 255% in the two bays. Average seasonal CH4 fluxes for the two bays varied between 0.5 ± 0.2 and 6.0 ± 1.5 mg CH4/（m^2.day） while N20 varied between 0.4 ± 0.1 and 1.6 ± 0.6 mg N2O/（m^2-day）. Weighted emissions （t CO2-e） were 63%-90% N2O dominated implying that a reduction in N2O inputs and/or nitrogen availability in the bays may significantly reduce the bays＇ greenhouse gas （GHG） budget. Emissions data for tropical and subtropical systems is still scarce. This work found subtropical bays to be significant aquatic sources of both CH4 and N2O and puts the estimated fluxes into the global context with measurements done from other climatic regions.展开更多
This work investigated the sensitivity toward humidity, NO2 and H2 of ZnO modified sepiolite （Si12Mg8O30（OH）4.（H2O）4.8H2O）. To this aim, sepiolite powder was first modified by leaching magnesium ions in HCI then...This work investigated the sensitivity toward humidity, NO2 and H2 of ZnO modified sepiolite （Si12Mg8O30（OH）4.（H2O）4.8H2O）. To this aim, sepiolite powder was first modified by leaching magnesium ions in HCI then by precipitating nano-sized Zn-based compounds under basic conditions. A subse- quent thermal treatment at 550 ℃ for 1 h was performed. The powders were characterized by X-ray diffraction （XRD）, specific surface area measurements, thermogravimetric and differential thermal anal- ysis and field emission scanning electron microscopy, as well as high resolution transmission electron microscopy. The XRD patterns showed that all leached heat treated samples were made of anhydrous sepiolite and of ZnO. Sensors were then obtained by screen printing these materials onto commercial alumina substrates with Pt electrodes. All the investigated compositions were capable of detecting NO2 down to ppm level and 20 ppm H2, at an optimal working temperature of 300°C. These detection limits are in line with the current best results reported in literature.展开更多
A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron micro...A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.展开更多
In this study,graphene oxide was covalently immobilized on silica-coated magnetite and then modified with 2-phenylethylamine to give a nanocomposite of type Fe3O4@SiO2@GO-PEA that can be applied to the magnetic solid-...In this study,graphene oxide was covalently immobilized on silica-coated magnetite and then modified with 2-phenylethylamine to give a nanocomposite of type Fe3O4@SiO2@GO-PEA that can be applied to the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons（PAHs） from water samples.The resulting microspheres（Fe3O4@SiO2@GO-PEA） were characterized by Fourier transform-infrared spectroscopy（FT-IR）,scanning electron microscopy（SEM）,CHNS elemental analysis,and vibrating sample magnetometry（VSM） techniques.The adsorbent possesses the magnetic properties of Fe3O4 nanoparticles that allow them easily to be separated by an external magnetic field.They also have the high specific surface area of graphene oxide which improves adsorption capacity.Desorption conditions,extraction time,amount of adsorbent,salt concentration,and pH were investigated and optimized.Following desorption,the PAHs were quantified by gas chromatography with flame ionization detection（GC-FID）.The limits of detection（at an S/N ratio of 3） were achieved from 0.005 to0.1 μg/L with regression coefficients（R2） higher than 0.9954.The relative standard deviations（RSDs） were below 5.8%（intraday） and 6.2%（inter-day）,respectively.The method was successfully applied to the analysis of PAHs in environmental water samples where it showed recoveries in the range between 71.7%and 106.7%（with RSDs of 1.6%to 8.4%,for n = 3）.The results indicated that the Fe3O4@SiO2@GO-PEA microspheres had a great promise to extraction of PAHs from different water samples.展开更多
Recently, the quasi-two-dimensional electron gas （q2DEG） confined at the interface between LaAlO3 and SrTiO3 has attracted significant attention. In this paper, we briefly review experimental methods that have been ...Recently, the quasi-two-dimensional electron gas （q2DEG） confined at the interface between LaAlO3 and SrTiO3 has attracted significant attention. In this paper, we briefly review experimental methods that have been used to tune the carrier density and mobility of this q2DEG. These methods can be classified into two categories： growth-related tuning （i.e. substrate, growth temperature, oxygen pressure, post-annealing, LaAlO3 thickness, stoichiometry, and capping layers） and post-growth tuning （i.e. electrostatic field gating, conductive atomic force microscopy and surface adsorbates）. Taken together, these methods enable the broad tuning of the electronic properties of this interface.展开更多
Gasification experiments were carried out in a pilot scale fluid bed reactor operated under allothermal mode and low fluidisation regime with iron-doped olivine and char as catalyst for in-situ tar abatement.The catal...Gasification experiments were carried out in a pilot scale fluid bed reactor operated under allothermal mode and low fluidisation regime with iron-doped olivine and char as catalyst for in-situ tar abatement.The catalyst combination resulted in a reduction of 50%in the overall tar yield with respect to the reference values.Furthermore,the integration of an oxidative Hot Gas Filtration unit downstream the gasification reactor led to a further reduction in overall tar yield and relatively clean gas was obtained(approx.1 g/Nm3,benzene-free).The tar dew point of the resulting producer gas was estimated to 80℃,only 40℃ above the threshold value recommended for its valorisation in standard internal combustion engines.Moreover,catalyst elutriation and char hold-up took place to a large extent inside the reactor.The analysis of catalyst samples at different Time-On-Stream(TOS)revealed:(i)a considerable loss of iron oxides during the first hour of test because of the interparticle mechanical attrition(mostly surface abrasion)and partial reduction of hematite to magnetite and wustite but,stable composition at higher TOS,(ii)the loss of the iron oxide coverage of Fe/olivine particles and the formation of agglomerates with increasing TOS and,(iii)the amount of carbon deposited in the surface of the Fe/olivine particles increased with TOS,but in any case,these carbon deposits can be completely oxidized above 650℃.展开更多
A waste heat recovery and denitrification system was developed for improving energy conservation and emissions control especially for control of PM2.5 particles and haze. The system uses enhanced heat and mass transfe...A waste heat recovery and denitrification system was developed for improving energy conservation and emissions control especially for control of PM2.5 particles and haze. The system uses enhanced heat and mass transfer techniques in a packed heat exchange tower with self-rotation and zero-pressure spraying, low temperature NO oxidation by ozone, and neutralization with an alkali solution. Operating data in a test project gave NOx in the exhaust flue gas of less than 30 mg/Nm3 with an ozone addition rate of 8 kg/h and spray water p H of 7.5–8, an average heat recovery of 3 MW, and an average heat supply of 7.2 MW.展开更多
Metal oxide semiconductor gas sensors offer high sensitivity and low-cost gas detection.However,low selectivity and poor stability are significant challenges associated with these sensors.In this study,we designed a s...Metal oxide semiconductor gas sensors offer high sensitivity and low-cost gas detection.However,low selectivity and poor stability are significant challenges associated with these sensors.In this study,we designed a sheet-like stacked zinc oxide(ZnO)nanomaterial using ZIF-67 and prepared the nanomaterial AGCZ-2 by doping with gold-modified graphene oxide(GO).This material demonstrates rapid and sensitive detection of low concentrations of carbon monoxide(CO)gas and exhibits excellent selectivity towards CO.The crystal structure,microstructure,elemental composition,and pore size of the material were characterized and analyzed using XRD,FESEM,EDS elemental analysis,TEM,and N2 adsorption-desorption techniques.The CO gas sensing performance of the sensor prepared in this study was tested,and the results showed that the AGCZ-2 sensor,operating at an optimal temperature of 260℃,had a response value of 5.84 for 50 ppm CO,with response and recovery times of 103 s and 84 s,respectively.In terms of selectivity,the response of the AGCZ-2 sensor to CO was 3.84 times that of the second most sensitive gas(hydrogen),indicating excellent selectivity towards CO over hydrogen.Additionally,the sensor exhibited good stability and repeatability,with a relative standard deviation of 2.27% for the response values to 5 ppm CO gas over five consecutive tests.Over a 28-day testing period,the sensor’s response to 5 ppm CO exhibited a decay rate of 5.22%,with a relative standard deviation of 2.41.展开更多
The activated sludge process to remove nitrogen and biochemical oxygen demand （BOD） is reportedly cost-effective for swine wastewater treatment, and it use has thus increased in pig farming. Nitrous oxide （N20） is...The activated sludge process to remove nitrogen and biochemical oxygen demand （BOD） is reportedly cost-effective for swine wastewater treatment, and it use has thus increased in pig farming. Nitrous oxide （N20） is generated on farms as an intermediate product in nitrification and denitrification, and methane （CH4） is also generated from organic degradation under anaerobic conditions by microorganisms in manure or wastewater. This study was carried out at five activated sludge treatment facilities across Japan between August 2014 and January 2015. Measurements were conducted over several weeks at wastewater purification facilities for swine farms： two in Chiba prefecture （East Japan）, two in Okayama prefecture （West Japan）, and one in Saga （Southern Japan）. Taking several environmental fluctuations into account, we collected measurement data continuously day and night, during both high-temperature and low-temperature periods. The results indicated that CH4 and N20 emission factors were 0.91% （kgCHa·kg volatile solids^-1） and 2.87% （g N2O-N·kg total N^-1）, respectively. Ammonia emissions were negligible in all of the measurements from the wastewater facilities. The N20 emission factor calculated under this experiment was low compared to our previous finding （5.0%; g N2O-N·kg N^-1） in a laboratory experiment. In contrast, the CH4 emission factor calculated herein was rather high compared to the laboratory measurements. There was great variation in daily GHG emission factors measured in the actual wastewater treatment facilities. In particular, the N2O emission rate was affected by several environmental conditions at each facility location, as well as by the management of the wastewater treatment.展开更多
Various tungsten oxide-based nanomaterials have been prepared by a modified plasma arc gas condensation technique without the use of catalysts or substrates. These products could be obtained by controlling the process...Various tungsten oxide-based nanomaterials have been prepared by a modified plasma arc gas condensation technique without the use of catalysts or substrates. These products could be obtained by controlling the processing parameters during experiment. All the as-obtained samples were characterized by field emission gun scanning electron microscopy, high-resolution transmission electron microscopy, and X- ray diffraction techniques. The results revealed that as-prepared tungsten oxide nanomaterials （WO3, W190s5 and WsO14） with different phases and morphologies could be obtained by decreasing the oxygen content in the chamber. In addition, W18049 nanotubes and nanorod bundles were fabricated by con- trolling the Ar/O2 ratio under He plasma gas. W18Q9/TiO2 core-shell nanoparticles were also prepared by evaporating a dual target. The experimental results showed that the present technique is unique and feasible for the fabrication of nanomaterials for use in different applications.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51372041,51422202, and 21673048)the "Shu Guang" Project(No. 13SG02)supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation+3 种基金the National Youth Top-notch Talent Support Program in China, China Postdoctoral Science Foundation(No. KLH1615138)Shanghai Nature Science Foundation of China(Nos. 14ZR1416600 and 15ZR1402000)Shanghai Pujiang Program, China(No.16PJ1401100)the International Scientific Partnership Program ISPP at King Saud University for funding this research work through ISPP# 0094
文摘Among various gas sensing materials, metal oxide semiconductors have shown great potential as resistive type sensors. The ordered porous structural metal oxide semiconductors with well-defined meso- or macro-pores chemically synthesized via soft-templating method and nanocasting strategy have high porosity, highly interconnected pore channels and high surface area with enormous active sites for interacting with gaseous molecules. These features enable them good performance in gas sensing, including high sensitivity, fast response and recovery, good selectivity. This review gives a comprehensive summary about the porous metal oxides with focus on the synthesis methods, structure related properties, as well as the modification strategies for gas sensing improved performances.
基金supported by the National Natural Science Foundation of China (No. 51138009)
文摘Three full-scale wastewater treatment processes, Orbal oxidation ditch, anoxic/anaerobic/aerobic （reversed A^2O） and anaerobic/anoxic/aerobic （A^2O）, were selected to investigate the emission characteristics of greenhouse gases （GHG）, including carbon dioxide （CO2）, methane （CH4） and nitrous oxide （N2O）. Results showed that although the processes were different, the units presenting high GHG emission fluxes were remarkably similar, namely the highest CO2 and N2O emission fluxes occurred in the aerobic areas, and the highest CH4 emission fluxes occurred in the grit tanks. The GHG emission amount of each unit can be calculated from its area and GHG emission flux. The calculation results revealed that the maximum emission amounts of CO2, CH4 and N2O in the three wastewater treatment processes appeared in the aerobic areas in all cases. Theoretically, CH4 should be produced in anaerobic conditions, rather than aerobic conditions. However, results in this study showed that the CH4 emission fluxes in the forepart of the aerobic area were distinctly higher than in the anaerobic area. The situation for N2O was similar to that of CH4： the N2O emission flux in the aerobic area was also higher than that in the anoxic area. Through analysis of the GHG mass balance, it was found that the flow of dissolved GHG in the wastewater treatment processes and aerators may be the main reason for this phenomenon. Based on the monitoring and calculation results, GHG emission factors for the three wastewater treatment processes were determined. The A^2O process had the highest CO2 emission factor of 319.3 g CO2/kg CODremoved, and the highest CH4 and N2O emission factors of 3.3 g CH4/kg CODremoved and 3.6 g N2O/kg TNremoved were observed in the Orbal oxidation ditch process.
基金Project supported by the Ministry of Science and Technology of China(Grant Nos.2013CB921701,2013CBA01603,and 2014CB920903)the National Natural Science Foundation of China(Grant Nos.10974019,51172029,91121012,11422430,11374035,11474022,and 11474024)+1 种基金the Program for New Century Excellent Talents in the University of the Ministry of Education of China(Grant No.NCET-13-0054)the Beijing Higher Education Young Elite Teacher Project,China(Grant No.YETP0238)
文摘A systematic study of the two-dimensional electron gas at La AlO_3/SrTiO_3（110） interface reveals an anisotropy along two specific directions, [001] and 1ī0. The anisotropy becomes distinct for the interface prepared under high oxygen pressure with low carrier density. Angular dependence of magnetoresistance shows that the electron confinement is stronger along the 1ī0 direction. Gate-tunable magnetoresistance reveals a clear in-plane anisotropy of the spin–orbit coupling,and the spin relaxation mechanism along both directions belongs to D＇yakonov–Perel＇（DP） scenario. Moreover, in-plane anisotropic superconductivity is observed for the sample with high carrier density, the superconducting transition temperature is lower but the upper critical field is higher along the 1ī0 direction. This in-plane anisotropy could be ascribed to the anisotropic band structure along the two crystallographic directions.
基金supported by the Research Program of State Key Laboratory of Lake Science and Environment(No.2012SKL012)CAS Key Project(No.KJZD-EW-TZ-G10)+1 种基金the National Basic Research Program(973)of China(No.2012CB417005)the Poyang Lake Wetland Integrated Research Station for their help on field study
文摘Most aquatic ecosystems contribute elevated N2 O to atmosphere due to increasing anthropogenic nitrogen loading. To further understand the spatial heterogeneity along an aquatic continuum from the upriver to wetland to lake to downriver, the study was conducted on spatial variations in N2 O emission along Poyang Lake aquatic continuum during the flood season from 15 July 2013 to 10 August 2013. The results showed the N2 O concentrations, the ratio of N2O/dinitrogen（N2） gases production, N2 O emission and denitrification rates ranged from 0.10 to 1.11 μg N/L,- 0.007% to 0.051%,- 9.73 to 127 μg N/m2/hr and 1.33 × 104to31.9 × 104μg N2/m2/hr, respectively, across the continuum. The average N2 O concentrations,the ratio of N2O/N2 and N2O emission was significantly lower in wetlands as compared to the rivers and lake（p 〈 0.01）. The significantly high denitrification rate and low N2 O emission together highlighted that most N2 O can be converted into N2 via near complete denitrification in the Poyang Lake wetlands. Our study suggests that the wetlands might impact N2 O budget in an integrated aquatic ecosystems. Moreover, N2 O emission from different aquatic ecosystem should be considered separately when quantifying the regional budget in aquatic ecosystem.
基金funded by the Australian Research Council (ARC), Healthy Waterways LtdSeqwater through an industry linkage grant (ARC Linkage project # LP100100325)
文摘Surface water methane （CH4） and nitrous oxide （N20） concentrations and fluxes were investigated in two subtropical coastal embayments （Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia）. Measurements were done at 23 stations in seven campaigns covering different seasons during 2010-2012. Water-air fluxes were estimated using the Thin Boundary Layer approach with a combination of wind and currents-based models for the estimation of the gas transfer velocities. The two bays were strong sources of both CH4 and N2O with no significant differences in the degree of saturation of both gases between them during all measurement campaigns. Both CH4 and N2O concentrations had strong temporal but minimal spatial variability in both bays. During the seven seasons, CH4 varied between 500% and 4000% saturation while N2O varied between 128 and 255% in the two bays. Average seasonal CH4 fluxes for the two bays varied between 0.5 ± 0.2 and 6.0 ± 1.5 mg CH4/（m^2.day） while N20 varied between 0.4 ± 0.1 and 1.6 ± 0.6 mg N2O/（m^2-day）. Weighted emissions （t CO2-e） were 63%-90% N2O dominated implying that a reduction in N2O inputs and/or nitrogen availability in the bays may significantly reduce the bays＇ greenhouse gas （GHG） budget. Emissions data for tropical and subtropical systems is still scarce. This work found subtropical bays to be significant aquatic sources of both CH4 and N2O and puts the estimated fluxes into the global context with measurements done from other climatic regions.
基金the financial support of Erasmus-Mundus program(FFEEBB project Action 2(scholarship application number L020900787) and EMECW,WELCOME Project Action 2(scholarship application number WELC11011869),Coordination Office:Politecnico di Torino,Turin,Italy,respectively)
文摘This work investigated the sensitivity toward humidity, NO2 and H2 of ZnO modified sepiolite （Si12Mg8O30（OH）4.（H2O）4.8H2O）. To this aim, sepiolite powder was first modified by leaching magnesium ions in HCI then by precipitating nano-sized Zn-based compounds under basic conditions. A subse- quent thermal treatment at 550 ℃ for 1 h was performed. The powders were characterized by X-ray diffraction （XRD）, specific surface area measurements, thermogravimetric and differential thermal anal- ysis and field emission scanning electron microscopy, as well as high resolution transmission electron microscopy. The XRD patterns showed that all leached heat treated samples were made of anhydrous sepiolite and of ZnO. Sensors were then obtained by screen printing these materials onto commercial alumina substrates with Pt electrodes. All the investigated compositions were capable of detecting NO2 down to ppm level and 20 ppm H2, at an optimal working temperature of 300°C. These detection limits are in line with the current best results reported in literature.
基金financially supported by the National Natural Science Foundation of China (Nos. 51004060, 51104074, and 51174105)the Natural Science Foundation of Yunnan Province (No. 2010ZC018)
文摘A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.
文摘In this study,graphene oxide was covalently immobilized on silica-coated magnetite and then modified with 2-phenylethylamine to give a nanocomposite of type Fe3O4@SiO2@GO-PEA that can be applied to the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons（PAHs） from water samples.The resulting microspheres（Fe3O4@SiO2@GO-PEA） were characterized by Fourier transform-infrared spectroscopy（FT-IR）,scanning electron microscopy（SEM）,CHNS elemental analysis,and vibrating sample magnetometry（VSM） techniques.The adsorbent possesses the magnetic properties of Fe3O4 nanoparticles that allow them easily to be separated by an external magnetic field.They also have the high specific surface area of graphene oxide which improves adsorption capacity.Desorption conditions,extraction time,amount of adsorbent,salt concentration,and pH were investigated and optimized.Following desorption,the PAHs were quantified by gas chromatography with flame ionization detection（GC-FID）.The limits of detection（at an S/N ratio of 3） were achieved from 0.005 to0.1 μg/L with regression coefficients（R2） higher than 0.9954.The relative standard deviations（RSDs） were below 5.8%（intraday） and 6.2%（inter-day）,respectively.The method was successfully applied to the analysis of PAHs in environmental water samples where it showed recoveries in the range between 71.7%and 106.7%（with RSDs of 1.6%to 8.4%,for n = 3）.The results indicated that the Fe3O4@SiO2@GO-PEA microspheres had a great promise to extraction of PAHs from different water samples.
基金Project supported by the Department of Energy,Office of Basic Energy Sciences(Grant No.DE-AC02-76SF00515)
文摘Recently, the quasi-two-dimensional electron gas （q2DEG） confined at the interface between LaAlO3 and SrTiO3 has attracted significant attention. In this paper, we briefly review experimental methods that have been used to tune the carrier density and mobility of this q2DEG. These methods can be classified into two categories： growth-related tuning （i.e. substrate, growth temperature, oxygen pressure, post-annealing, LaAlO3 thickness, stoichiometry, and capping layers） and post-growth tuning （i.e. electrostatic field gating, conductive atomic force microscopy and surface adsorbates）. Taken together, these methods enable the broad tuning of the electronic properties of this interface.
基金the ADEME,France(Adelither-project N◦1702C0042)the Region Grand-Est,France(Feder Project Hy-C-Green)for the financial support.
文摘Gasification experiments were carried out in a pilot scale fluid bed reactor operated under allothermal mode and low fluidisation regime with iron-doped olivine and char as catalyst for in-situ tar abatement.The catalyst combination resulted in a reduction of 50%in the overall tar yield with respect to the reference values.Furthermore,the integration of an oxidative Hot Gas Filtration unit downstream the gasification reactor led to a further reduction in overall tar yield and relatively clean gas was obtained(approx.1 g/Nm3,benzene-free).The tar dew point of the resulting producer gas was estimated to 80℃,only 40℃ above the threshold value recommended for its valorisation in standard internal combustion engines.Moreover,catalyst elutriation and char hold-up took place to a large extent inside the reactor.The analysis of catalyst samples at different Time-On-Stream(TOS)revealed:(i)a considerable loss of iron oxides during the first hour of test because of the interparticle mechanical attrition(mostly surface abrasion)and partial reduction of hematite to magnetite and wustite but,stable composition at higher TOS,(ii)the loss of the iron oxide coverage of Fe/olivine particles and the formation of agglomerates with increasing TOS and,(iii)the amount of carbon deposited in the surface of the Fe/olivine particles increased with TOS,but in any case,these carbon deposits can be completely oxidized above 650℃.
基金supported by the National Basic Research Program of China(Grant No.2013CB228301)
文摘A waste heat recovery and denitrification system was developed for improving energy conservation and emissions control especially for control of PM2.5 particles and haze. The system uses enhanced heat and mass transfer techniques in a packed heat exchange tower with self-rotation and zero-pressure spraying, low temperature NO oxidation by ozone, and neutralization with an alkali solution. Operating data in a test project gave NOx in the exhaust flue gas of less than 30 mg/Nm3 with an ozone addition rate of 8 kg/h and spray water p H of 7.5–8, an average heat recovery of 3 MW, and an average heat supply of 7.2 MW.
基金funded by the National Basic Research Program of China(grant no.2022YFB3206803)the National Science Foundation of China Project(grant numbers 62174163).
文摘Metal oxide semiconductor gas sensors offer high sensitivity and low-cost gas detection.However,low selectivity and poor stability are significant challenges associated with these sensors.In this study,we designed a sheet-like stacked zinc oxide(ZnO)nanomaterial using ZIF-67 and prepared the nanomaterial AGCZ-2 by doping with gold-modified graphene oxide(GO).This material demonstrates rapid and sensitive detection of low concentrations of carbon monoxide(CO)gas and exhibits excellent selectivity towards CO.The crystal structure,microstructure,elemental composition,and pore size of the material were characterized and analyzed using XRD,FESEM,EDS elemental analysis,TEM,and N2 adsorption-desorption techniques.The CO gas sensing performance of the sensor prepared in this study was tested,and the results showed that the AGCZ-2 sensor,operating at an optimal temperature of 260℃,had a response value of 5.84 for 50 ppm CO,with response and recovery times of 103 s and 84 s,respectively.In terms of selectivity,the response of the AGCZ-2 sensor to CO was 3.84 times that of the second most sensitive gas(hydrogen),indicating excellent selectivity towards CO over hydrogen.Additionally,the sensor exhibited good stability and repeatability,with a relative standard deviation of 2.27% for the response values to 5 ppm CO gas over five consecutive tests.Over a 28-day testing period,the sensor’s response to 5 ppm CO exhibited a decay rate of 5.22%,with a relative standard deviation of 2.41.
文摘The activated sludge process to remove nitrogen and biochemical oxygen demand （BOD） is reportedly cost-effective for swine wastewater treatment, and it use has thus increased in pig farming. Nitrous oxide （N20） is generated on farms as an intermediate product in nitrification and denitrification, and methane （CH4） is also generated from organic degradation under anaerobic conditions by microorganisms in manure or wastewater. This study was carried out at five activated sludge treatment facilities across Japan between August 2014 and January 2015. Measurements were conducted over several weeks at wastewater purification facilities for swine farms： two in Chiba prefecture （East Japan）, two in Okayama prefecture （West Japan）, and one in Saga （Southern Japan）. Taking several environmental fluctuations into account, we collected measurement data continuously day and night, during both high-temperature and low-temperature periods. The results indicated that CH4 and N20 emission factors were 0.91% （kgCHa·kg volatile solids^-1） and 2.87% （g N2O-N·kg total N^-1）, respectively. Ammonia emissions were negligible in all of the measurements from the wastewater facilities. The N20 emission factor calculated under this experiment was low compared to our previous finding （5.0%; g N2O-N·kg N^-1） in a laboratory experiment. In contrast, the CH4 emission factor calculated herein was rather high compared to the laboratory measurements. There was great variation in daily GHG emission factors measured in the actual wastewater treatment facilities. In particular, the N2O emission rate was affected by several environmental conditions at each facility location, as well as by the management of the wastewater treatment.
基金the financial support of this work by the National Science Council of Taiwan, China under grant number NSC 98-2221-E-027-035-MY3
文摘Various tungsten oxide-based nanomaterials have been prepared by a modified plasma arc gas condensation technique without the use of catalysts or substrates. These products could be obtained by controlling the processing parameters during experiment. All the as-obtained samples were characterized by field emission gun scanning electron microscopy, high-resolution transmission electron microscopy, and X- ray diffraction techniques. The results revealed that as-prepared tungsten oxide nanomaterials （WO3, W190s5 and WsO14） with different phases and morphologies could be obtained by decreasing the oxygen content in the chamber. In addition, W18049 nanotubes and nanorod bundles were fabricated by con- trolling the Ar/O2 ratio under He plasma gas. W18Q9/TiO2 core-shell nanoparticles were also prepared by evaporating a dual target. The experimental results showed that the present technique is unique and feasible for the fabrication of nanomaterials for use in different applications.
