Nitrous Oxide (N2O Emissions by Termites: Does the Feeding Guild Matter?

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Alain Brauman

Full Text Available In the tropics, termites are major players in the mineralization of organic matter leading to the production of greenhouse gases including nitrous oxide (N2O. Termites have a wide trophic diversity and their N-metabolism depends on the feeding guild. This study assessed the extent to which N2O emission levels were determined by termite feeding guild and tested the hypothesis that termite species feeding on a diet rich in N emit higher levels of N2O than those feeding on a diet low in N. An in-vitro incubation approach was used to determine the levels of N2O production in 14 termite species belonging to different feeding guilds, collected from a wide range of biomes. Fungus-growing and soil-feeding termites emit N2O. The N2O production levels varied considerably, ranging from 13.14 to 117.62 ng N2O-N d(-1 (g dry wt.(-1 for soil-feeding species, with Cubitermes spp. having the highest production levels, and from 39.61 to 65.61 ng N2O-N d(-1 (g dry wt.(-1 for fungus-growing species. Wood-feeding termites were net N2O consumers rather than N2O producers with a consumption ranging from 16.09 to 45.22 ng N2O-N d(-1 (g dry wt.(-1. Incubating live termites together with their mound increased the levels of N2O production by between 6 and 13 fold for soil-feeders, with the highest increase in Capritermes capricornis, and between 14 and 34 fold for fungus-growers, with the highest increase in Macrotermes muelleri. Ammonia-oxidizing (amoA-AOB and amoA-AOA and denitrifying (nirK, nirS, nosZ gene markers were detected in the guts of all termite species studied. No correlation was found between the abundance of these marker genes and the levels of N2O production from different feeding guilds. Overall, these results support the hypothesis that N2O production rates were higher in termites feeding on substrates with higher N content, such as soil and fungi, compared to those feeding on N-poor wood.

Synthesis of visible-light responsive graphene oxide/TiO(2) composites with p/n heterojunction.

Science.gov (United States)

Chen, Chao; Cai, Weimin; Long, Mingce; Zhou, Baoxue; Wu, Yahui; Wu, Deyong; Feng, Yujie

2010-11-23

Graphene oxide/TiO(2) composites were prepared by using TiCl(3) and graphene oxide as reactants. The concentration of graphene oxide in starting solution played an important role in photoelectronic and photocatalytic performance of graphene oxide/TiO(2) composites. Either a p-type or n-type semiconductor was formed by graphene oxide in graphene oxide/TiO(2) composites. These semiconductors could be excited by visible light with wavelengths longer than 510 nm and acted as sensitizer in graphene oxide/TiO(2) composites. Visible-light driven photocatalytic performance of graphene oxide/TiO(2) composites in degradation of methyl orange was also studied. Crystalline quality and chemical states of carbon elements from graphene oxide in graphene oxide/TiO(2) composites depended on the concentration of graphene oxide in the starting solution. This study shows a possible way to fabricate graphene oxide/semiconductor composites with different properties by using a tunable semiconductor conductivity type of graphene oxide.

MLS/Aura Level 2 Nitrous Oxide (N2O) Mixing Ratio V004

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National Aeronautics and Space Administration — ML2N2O is the EOS Aura Microwave Limb Sounder (MLS) standard product for nitrous oxide derived from radiances measured primarily by the 640 GHz radiometer (Band 12)...

Co-Mn-Al Mixed Oxides as Catalysts for Ammonia Oxidation to N2O.

Czech Academy of Sciences Publication Activity Database

Ludvíková, Jana; Jablońska, M.; Jirátová, Květa; Chmielarz, L.; Balabánová, Jana; Kovanda, F.; Obalová, L.

2016-01-01

Roč. 42, č. 3 (2016), s. 2669-2690 ISSN 0922-6168 R&D Projects: GA ČR GA14-13750S Institutional support: RVO:67985858 Keywords : Co-Mn-Al mixed oxide s * catalytic ammonia oxidation * N2O production * mechanochemical production Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.369, year: 2016

Ammonia oxidation pathways and nitrifier denitrification are significant sources of N2O and NO under low oxygen availability.

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Zhu, Xia; Burger, Martin; Doane, Timothy A; Horwath, William R

2013-04-16

The continuous increase of nitrous oxide (N2O) abundance in the atmosphere is a global concern. Multiple pathways of N2O production occur in soil, but their significance and dependence on oxygen (O2) availability and nitrogen (N) fertilizer source are poorly understood. We examined N2O and nitric oxide (NO) production under 21%, 3%, 1%, 0.5%, and 0% (vol/vol) O2 concentrations following urea or ammonium sulfate [(NH4)2SO4] additions in loam, clay loam, and sandy loam soils that also contained ample nitrate. The contribution of the ammonia (NH3) oxidation pathways (nitrifier nitrification, nitrifier denitrification, and nitrification-coupled denitrification) and heterotrophic denitrification (HD) to N2O production was determined in 36-h incubations in microcosms by (15)N-(18)O isotope and NH3 oxidation inhibition (by 0.01% acetylene) methods. Nitrous oxide and NO production via NH3 oxidation pathways increased as O2 concentrations decreased from 21% to 0.5%. At low (0.5% and 3%) O2 concentrations, nitrifier denitrification contributed between 34% and 66%, and HD between 34% and 50% of total N2O production. Heterotrophic denitrification was responsible for all N2O production at 0% O2. Nitrifier denitrification was the main source of N2O production from ammonical fertilizer under low O2 concentrations with urea producing more N2O than (NH4)2SO4 additions. These findings challenge established thought attributing N2O emissions from soils with high water content to HD due to presumably low O2 availability. Our results imply that management practices that increase soil aeration, e.g., reducing compaction and enhancing soil structure, together with careful selection of fertilizer sources and/or nitrification inhibitors, could decrease N2O production in agricultural soils.

Arbuscular mycorrhizal fungi reduce nitrous oxide emissions from N2 O hotspots.

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Storer, Kate; Coggan, Aisha; Ineson, Phil; Hodge, Angela

2017-12-05

Nitrous oxide (N 2 O) is a potent, globally important, greenhouse gas, predominantly released from agricultural soils during nitrogen (N) cycling. Arbuscular mycorrhizal fungi (AMF) form a mutualistic symbiosis with two-thirds of land plants, providing phosphorus and/or N in exchange for carbon. As AMF acquire N, it was hypothesized that AMF hyphae may reduce N 2 O production. AMF hyphae were either allowed (AMF) or prevented (nonAMF) access to a compartment containing an organic matter and soil patch in two independent microcosm experiments. Compartment and patch N 2 O production was measured both before and after addition of ammonium and nitrate. In both experiments, N 2 O production decreased when AMF hyphae were present before inorganic N addition. In the presence of AMF hyphae, N 2 O production remained low following ammonium application, but increased in the nonAMF controls. By contrast, negligible N 2 O was produced following nitrate application to either AMF treatment. Thus, the main N 2 O source in this system appeared to be via nitrification, and the production of N 2 O was reduced in the presence of AMF hyphae. It is hypothesized that AMF hyphae may be outcompeting slow-growing nitrifiers for ammonium. This has significant global implications for our understanding of soil N cycling pathways and N 2 O production. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Thermochemical characteristics of La n+1Ni nO3n+1 oxides

International Nuclear Information System (INIS)

Bannikov, D.O.; Safronov, A.P.; Cherepanov, V.A.

2006-01-01

Lanthanum nickelates: La 2 NiO 4+δ , La 3 Ni 2 O 7-δ , La 4 Ni 3 O 10-δ and LaNiO 3-δ the members of Ruddlesden-Popper series La n+1 Ni n O 3n+1 were prepared using citrate route. Dissolution enthalpies of complex oxides as well as a number of subsidiary substances were measured by means of Calvet calorimeter in 1 M solution of hydrochloric acid at 25 deg. C. The dissolution scheme of complex oxides in hydrochloric acid was proposed and enthalpies of formation of the complex oxides from binary oxides were calculated considering oxygen nonstoichiometry of these substances. Enthalpies of step-by-step oxidation were evaluated. Partial enthalpy contribution of LaO layers was calculated endothermic equals to 30.9 J/mol while partial enthalpy contribution of perovskite LaNiO 3 layers was negative equals to -97.0 J/mol. Enthalpy of formation of any complex oxide of Ruddlesden-Popper series fits very well to the linear regression based on these values

Emissions of nitrous acid (HONO), nitric oxide (NO) and nitrous oxide (N2O) from boreal agricultural soil - Effect of N fertilization

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Bhattarai, Hem Raj; Virkajärvi, Perttu; -Yli Pirilä, Pasi; Maljanen, Marja

2017-04-01

There is no doubt that nitrogen (N) fertilization has crucial role in increasing food production. However, in parallel it can cause severe impact in environment such as eutrophication, surface/groundwater pollution via nitrate (NO3-) leaching and emissions of N trace gases. Fertilization increases the emissions of nitrous oxide (N2O) which is 260 stronger greenhouse gas than carbon dioxide (CO2). It also enhances the emissions of nitric oxide (NO); an oxidized and very reactive form of nitrogen which can fluctuate the ozone (O3) concentration in atmosphere and cause acidification. The effects of N- fertilization on the emission of N2O and NO from agricultural soil are well known. However, the effects of N fertilization on nitrous acid (HONO) emissions are unknown. Few studies have shown that HONO is emitted from soil but they lack to interlink fertilization and HONO emission. HONO accounts for 17-34 % of hydroxyl (OH-) radical production? in the atmosphere, OH- radicals have vital role in atmospheric chemistry; they can cause photochemical smog, form O3, oxidize volatile organic compounds and also atmospheric methane (CH4). We formulated hypothesis that N fertilization will increase the HONO emissions as it does for N2O and NO. To study this, we took soil samples from agricultural soil receiving different amount of N-fertilizer (0, 250 and 450 kg ha-1) in eastern Finland. HONO emissions were measured by dynamic chamber technique connected with LOPAP (Quma Elektronik & Analytik GmbH), NO by NOx analyzer (Thermo scientific) and static chamber technique and gas chromatograph was used for N2O gas sampling and analysis. Several soil parameters were also measured to establish the relationship between the soil properties, fertilization rate and HONO emission. This study is important because eventually it will open up more questions regarding the forms of N loss from soils and impact of fertilization on atmospheric chemistry.

Assessment of nitric oxide (NO) redox reactions contribution to nitrous oxide (N2 O) formation during nitrification using a multispecies metabolic network model.

Science.gov (United States)

Perez-Garcia, Octavio; Chandran, Kartik; Villas-Boas, Silas G; Singhal, Naresh

2016-05-01

Over the coming decades nitrous oxide (N2O) is expected to become a dominant greenhouse gas and atmospheric ozone depleting substance. In wastewater treatment systems, N2O is majorly produced by nitrifying microbes through biochemical reduction of nitrite (NO2(-)) and nitric oxide (NO). However it is unknown if the amount of N2O formed is affected by alternative NO redox reactions catalyzed by oxidative nitrite oxidoreductase (NirK), cytochromes (i.e., P460 [CytP460] and 554 [Cyt554 ]) and flavohemoglobins (Hmp) in ammonia- and nitrite-oxidizing bacteria (AOB and NOB, respectively). In this study, a mathematical model is developed to assess how N2O formation is affected by such alternative nitrogen redox transformations. The developed multispecies metabolic network model captures the nitrogen respiratory pathways inferred from genomes of eight AOB and NOB species. The performance of model variants, obtained as different combinations of active NO redox reactions, was assessed against nine experimental datasets for nitrifying cultures producing N2O at different concentration of electron donor and acceptor. Model predicted metabolic fluxes show that only variants that included NO oxidation to NO2(-) by CytP460 and Hmp in AOB gave statistically similar estimates to observed production rates of N2O, NO, NO2(-) and nitrate (NO3(-)), together with fractions of AOB and NOB species in biomass. Simulations showed that NO oxidation to NO2(-) decreased N2O formation by 60% without changing culture's NO2(-) production rate. Model variants including NO reduction to N2O by Cyt554 and cNor in NOB did not improve the accuracy of experimental datasets estimates, suggesting null N2O production by NOB during nitrification. Finally, the analysis shows that in nitrifying cultures transitioning from dissolved oxygen levels above 3.8 ± 0.38 to <1.5 ± 0.8 mg/L, NOB cells can oxidize the NO produced by AOB through reactions catalyzed by oxidative NirK. © 2015 Wiley Periodicals, Inc.

The use of CeO2-Co3O4 oxides as a catalyst for the reduction of N2O emission

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Rajska Maria

2016-01-01

Full Text Available The morphological characterization of a series of cobalt-cerium oxide composites prepared by the deposition of CeO2 onto Co3O4 powder with a molar ratio of cerium oxide to Co3O4 in the range of 0 to 1 was performed. The powders were also impregnated with a solution of K2CO3 to obtain the theoretical content of potassium atoms 2at·nm−2. To investigate the effect of adding specific amount of CeO2 on the catalytic activity, the X-ray diffraction, SEM-EDX, laser particle size distribution and BET surface area measurements were used. The catalysts were tested through the low-temperature decomposition of nitrous oxide in the temperature range of 50°C to 700°C. The addition of CeO2 and K always moved the temperature of a complete N2O conversion towards lower temperatures (480°C-540°C to 340°C-420°C. The best catalytic properties were shown by the samples in which the ratio of cerium oxide to cobalt oxide ranged from 0.4 to 0.7.

A Study on N{sub 2}O Direct Oxidation Process with Re-oxidation Annealing for the Improvement of Interface Properties in 4H-SiC MOS Capacitor

Energy Technology Data Exchange (ETDEWEB)

Cho, Doohyung; Park, Kunsik; Yoo, Seongwook; Kim, Sanggi; Lee, Jinhwan; Kim, Kwangsoo [Electronics and Telecommunications Research Institute (ETRI), Daejeon (Korea, Republic of)

2017-08-15

The effect of N{sub 2}O direct oxidation processes with re-oxidation on SiC/SiO{sub 2} interface characteristics has been investigated. With different oxidation and post oxidation annealing (POA) processes, the flat-band voltage, effective dielectric charge density, and interface trap density are obtained from the capacitance-voltage curves. For the proposed N{sub 2}O direct oxidation processes with re-oxidation, oxides were grown in N{sub 2}O ambient, diluted in high-purity N{sub 2} to 10% concentration, for 5 h at 1230 ℃. After the growth, some samples were annealed additionally at 1200 ℃ in O{sub 2} or H{sub 2}O for 20 min. N{sub 2}O direct oxidation with re-oxidation processes was confirmed that SiC/SiO{sub 2} interface properties and dielectric stability have better performance than with other conventional oxidation processes. This oxidation technique is expected to improve gate dielectric stability for application to SiC MOS devices; in particular, it can be used to obtain high-quality SiC/SiO{sub 2} interface properties.

Highly efficient alkane oxidation catalyzed by [Mn(V)(N)(CN)4](2-). Evidence for [Mn(VII)(N)(O)(CN)4](2-) as an active intermediate.

Science.gov (United States)

Ma, Li; Pan, Yi; Man, Wai-Lun; Kwong, Hoi-Ki; Lam, William W Y; Chen, Gui; Lau, Kai-Chung; Lau, Tai-Chu

2014-05-28

The oxidation of various alkanes catalyzed by [Mn(V)(N)(CN)4](2-) using various terminal oxidants at room temperature has been investigated. Excellent yields of alcohols and ketones (>95%) are obtained using H2O2 as oxidant and CF3CH2OH as solvent. Good yields (>80%) are also obtained using (NH4)2[Ce(NO3)6] in CF3CH2OH/H2O. Kinetic isotope effects (KIEs) are determined by using an equimolar mixture of cyclohexane (c-C6H12) and cyclohexane-d12 (c-C6D12) as substrate. The KIEs are 3.1 ± 0.3 and 3.6 ± 0.2 for oxidation by H2O2 and Ce(IV), respectively. On the other hand, the rate constants for the formation of products using c-C6H12 or c-C6D12 as single substrate are the same. These results are consistent with initial rate-limiting formation of an active intermediate between [Mn(N)(CN)4](2-) and H2O2 or Ce(IV), followed by H-atom abstraction from cyclohexane by the active intermediate. When PhCH2C(CH3)2OOH (MPPH) is used as oxidant for the oxidation of c-C6H12, the major products are c-C6H11OH, c-C6H10O, and PhCH2C(CH3)2OH (MPPOH), suggesting heterolytic cleavage of MPPH to generate a Mn═O intermediate. In the reaction of H2O2 with [Mn(N)(CN)4](2-) in CF3CH2OH, a peak at m/z 628.1 was observed in the electrospray ionization mass spectrometry, which is assigned to the solvated manganese nitrido oxo species, (PPh4)[Mn(N)(O)(CN)4](-)·CF3CH2OH. On the basis of the experimental results the proposed mechanism for catalytic alkane oxidation by [Mn(V)(N)(CN)4](2-)/ROOH involves initial rate-limiting O-atom transfer from ROOH to [Mn(N)(CN)4](2-) to generate a manganese(VII) nitrido oxo active species, [Mn(VII)(N)(O)(CN)4](2-), which then oxidizes alkanes (R'H) via a H-atom abstraction/O-rebound mechanism. The proposed mechanism is also supported by density functional theory calculations.

Ammonium sorption and ammonia inhibition of nitrite-oxidizing bacteria explain contrasting soil N2O production

Science.gov (United States)

Venterea, R. T.; Sadowsky, M.; Breuillin-Sessoms, F.; Wang, P.; Clough, T. J.; Coulter, J. A.

2015-12-01

Better understanding of process controls over nitrous oxide (N2O) production in urine-impacted 'hot spots' and fertilizer bands is needed to improve mitigation strategies and emission models. Following amendment with bovine (Bos taurus) urine (Bu) or urea (Ur), we measured inorganic N, pH, N2O, and genes associated with nitrification in two soils ('L' and 'W') having similar texture, pH, C, and C/N ratio. Solution-phase ammonia (slNH3) was also calculated accounting for non-linear ammonium (NH4+) sorption capacities (ASC). Soil W displayed greater nitrification rates and nitrate (NO3-) levels than soil L, but was more resistant to nitrite (NO2-) accumulation and produced two to ten times less N2O than soil L. Genes associated with NO2- oxidation (nxrA) increased substantially in soil W but remained static in soil L. Soil NO2- was strongly correlated with N2O production, and cumulative (c-) slNH3 explained 87% of the variance in c-NO2-. Differences between soils were explained by greater slNH3 in soil L which inhibited NO2- oxidization leading to greater NO2- levels and N2O production. This is the first study to correlate the dynamics of soil slNH3, NO2-, N2O and nitrifier genes, and the first to show how ASC can regulate NO2- levels and N2O production.

Oxidation of a [Cu2S] complex by N2O and CO2: insights into a role of tetranuclearity in the CuZ site of nitrous oxide reductase.

Science.gov (United States)

Bagherzadeh, Sharareh; Mankad, Neal P

2018-01-25

Oxidation of a [Cu 2 (μ-S)] complex by N 2 O or CO 2 generated a [Cu 2 (μ-SO 4 )] product. In the presence of a sulfur trap, a [Cu 2 (μ-O)] species also formed from N 2 O. A [Cu 2 (μ-CS 3 )] species derived from CS 2 modeled initial reaction intermediates. These observations indicate that one role of tetranuclearity in the Cu Z catalytic site of nitrous oxide reductase is to protect the crucial S 2- ligand from oxidation.

Hazards of TiO2 and amorphous SiO2 nanoparticles

NARCIS (Netherlands)

Reijnders, L.; Kahn, H.A.; Arif, I.A.

2012-01-01

TiO2 and amorphous SiO2 nanoparticles have been described as ‘safe’, ‘non-toxic’ and ‘environment friendly’ in scientific literature. However, though toxicity data are far from complete, there is evidence that these nanoparticles are hazardous. TiO2 nanoparticles have been found hazardous to humans

Studies on nitrogen oxides (NOx and N2O) in pressurized fluidized bed combustion

International Nuclear Information System (INIS)

Lu Yong

1998-01-01

This thesis describes the experimental studies of nitrogen oxide (NO, NO 2 , N 2 O) emissions in pressurized fluidized bed combustion (PFBC). In the first part of the thesis the background and the objectives of this study are introduced. The second part summarizes the fundamental knowledge about the formation and destruction of nitrogen oxides in coal combustion, particularly in the conditions of PFBC. The instrumentation of test facilities, measurement and data analysis is described in the third part. Then the most important experimental results follow in the next parts. The forth part describes the results from a PFBC test rig and an empirical modelling for predicting the emissions of NO x and N 2 O. Finally, the fundamental work on coal combustion and fuel nitrogen conversion in a PFBC batch reactor is presented. These studies clearly confirm the potential of PFBC technology in the control nitrogen of oxide emissions. The research in the test rig was concentrated on determining the effects of process parameters on the emissions of nitrogen oxides with different fuels. Another objective was to examine the reduction of nitrogen oxides with the control methods in PFBC conditions, including ammonia injection and air staging combustion for reducing NO, and high temperature operations for reducing N 2 0. The results indicate that pressurized operation suppresses the conversion of fuel-N to nitrogen oxides and favors with employing the reduction methods for further nitrogen oxide reduction, for instance the temperature window of NO reduction with ammonia injection has been found to be widened to even lower temperature range. Maximum reductions of 80-85 % with ammonia injection and 75-80 % with air staging combustion were achieved in the conditions examined. Considerably low emissions of N 2 O ( 2 O control, and thermal decomposition proved to be the laming pathway of N 2 O destruction in PFBC. In the examined pressure range, increasing pressure causes a decrease of NO

Nitrous oxide (N2O). Emission inventory and options for control in the Netherlands

NARCIS (Netherlands)

Kroeze C; LAE

1994-01-01

This study was initiated to overview current knowledge on nitrous oxide (N2O). The report reviews atmospheric behaviour of N2O, global sources and sinks, Dutch emissions in 1990, options to reduce emissions, and past and future emissions. Despite the uncertainties involved, it is likely that without

The azido oxide N3O

International Nuclear Information System (INIS)

Petris, Giulia de; Troiani, Anna; Rosi, Marzio; Sgamellotti, Antonio; Cipollini, Romano

2012-01-01

Graphical abstract: N 3 O + ions prepared in the source of a mass spectrometer under low-pressure conditions are submitted to neutralization by collisional electron transfer, leading to the observation of the novel N 3 O oxide. Highlights: ► The study reports the positive detection in the gas phase of the novel azido oxide N 3 O. ► It has been prepared by collisional electron transfer to the N 3 O + ion and observed on a microsecond time scale. ► The oxide has been assigned a minimum lifetime of 0.7 μs and an open-chain structure of NNNO connectivity. ► The study examines the role of excited species in the formation of covalently bound ions suitable to neutralization. - Abstract: The new nitrogen-rich oxide N 3 O has been detected in the gas phase by mass spectrometric experiments. The radical has been assigned a minimum lifetime of 0.7 μs and an open-chain NNNO structure in the quartet state. Structures and energies of the N 3 O + precursor ion and the N 3 O radical have been investigated by ab initio calculations.

Nitrous Oxide (N2O) Emissions from Vehicles

International Nuclear Information System (INIS)

Becker, K.H.; Kurtenbach, R.; Lorzer, J.C.; Wiesen, P.; Jensen, T.; Wallington, T.J.

2000-01-01

N2O is an important greenhouse gas and accurate emission data are required to assess its impact on global climate. It is well established that automobiles, particularly those equipped with 3-way catalysts, emit N2O. However, the vehicle contribution to the global N2O budget is uncertain. We report results of N2O emission measurements performed in a road tunnel in Germany and using a chassis dynamometer system in the USA. We estimate that the global vehicle fleet emits (0.12±0.06) Tg yr-1 of N2O. From the emission factor (g N2O/g CO2) determined an annual N2O emission of (0.12±0.06) Tg yr-1 of N2O (0.08±0.04 Tg N yr-1) for the global vehicle fleet has been estimated which represents 1-4% of the atmospheric growth rate of this species. 9 refs

Oxide p-n Heterojunction of Cu2O/ZnO Nanowires and Their Photovoltaic Performance

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Seung Ki Baek

2013-01-01

Full Text Available Oxide p-n heterojunction devices consisting of p-Cu2O/n-ZnO nanowires were fabricated on ITO/glass substrates and their photovoltaic performances were investigated. The vertically arrayed ZnO nanowires were grown by metal organic chemical vapor deposition, which was followed by the electrodeposition of the p-type Cu2O layer. Prior to the fabrication of solar cells, the effect of bath pH on properties of the absorber layers was studied to determine the optimal condition of the Cu2O electrodeposition process. With the constant pH 11 solution, the Cu2O layer preferred the (111 orientation, which gave low electrical resistivity and high optical absorption. The Cu2O (pH 11/ZnO nanowire-based solar cell exhibited a higher conversion efficiency of 0.27% than the planar structure solar cell (0.13%, because of the effective charge collection in the long wavelength region and because of the enhanced junction area.

Effects of temperature on nitrous oxide (N2O) emission from intensive aquaculture system.

Science.gov (United States)

Paudel, Shukra Raj; Choi, Ohkyung; Khanal, Samir Kumar; Chandran, Kartik; Kim, Sungpyo; Lee, Jae Woo

2015-06-15

This study examines the effects of temperature on nitrous oxide (N2O) emissions in a bench-scale intensive aquaculture system rearing Koi fish. The water temperature varied from 15 to 24 °C at interval of 3 °C. Both volumetric and specific rate for nitrification and denitrification declined as the temperature decreased. The concentrations of ammonia and nitrite, however, were lower than the inhibitory level for Koi fish regardless of temperature. The effects of temperature on N2O emissions were significant, with the emission rate and emission factor increasing from 1.11 to 1.82 mg N2O-N/d and 0.49 to 0.94 mg N2O-N/kg fish as the temperature decreased from 24 to 15 °C. A global map of N2O emission from aquaculture was established by using the N2O emission factor depending on temperature. This study demonstrates that N2O emission from aquaculture is strongly dependent on regional water temperatures as well as on fish production. Copyright © 2015 Elsevier B.V. All rights reserved.

A p-n heterojunction of CuI/TiO2 with enhanced photoelectrocatalytic activity for methanol electro-oxidation

International Nuclear Information System (INIS)

Sun, Mingjuan; Hu, Jiayue; Zhai, Chunyang; Zhu, Mingshan; Pan, Jianguo

2017-01-01

Highlights: •A p-n heterojunction of CuI/TiO 2 is constructed. •CuI/TiO 2 is used as the support for depositing Pt nanoparticles. •Enhanced catalytic activity of MOR by using Pt-CuI/TiO 2 under light irradiation. •Improved charger separation contributes to enhanced photoelectrocatalytic activity. -- Abstract: In this paper, a p-n heterojunction including p-type CuI and n-type TiO 2 is first time constructed to be the support for the deposition of Pt. The as-prepared Pt-CuI/TiO 2 modified electrode is studied for the electrocatalytic oxidation of methanol both in dark and under light illumination. Compare to traditional electrocatalytic oxidation, the electrocatalytic activity of Pt-CuI/TiO 2 for methanol oxidation is improved with 4.0 times upon light illumination. Moreover, compare to bare CuI and TiO 2 upon light illumination, the heterostructure of CuI/TiO 2 displays 4.3 and 9.1 times enhanced electrocatalytic activity for methanol oxidation, respectively. The synergistic effects of photocatalysis and electrocatalysis as well as the effective charge transport in the p-n heterojunction of Pt-CuI/TiO 2 contribute such big enhancement. The present studies indicate that the constructing of p-n heterojunction provides more insights in the fields of photoelectrochemical and photo–assisted fuel cell system.

Comparative analysis of oxidative synthesis of N-alkyl, N,N-dialkyl and N-cykloalkyl-O-isobutyl thioncarbamate

Directory of Open Access Journals (Sweden)

Sovrlić Milica Ž.

2011-01-01

Full Text Available A optimized synthesis of N-alkyl, N,N-dialkyl- and N-cycloalkyl-O-isobutyl thioncarbamates by aminolysis of sodium isobutylxanthogenic acid (NaiBXAc and primary, secondary and cycloalkyl amines was developed at laboratory scale and applied at semi-industrial level. Studies on dependence of N-n-propyl-O-isopropylthiocarbamate yield and purity with respect to reaction parameters: reaction time and molar ratio of n-propylamine and NaiBXAc, were performed. In such way, optimal reaction conditions for synthesis of N-alkyl, N,N-dialkyl- and N-cycloalkyl-O-isobutyl thioncarbamates, by aminolysis of NaiBXAc, were established. Also, comparative results of thioncarbamates synthesis starting from potassium isobutyl xanthate (KiBX and corresponding amines in presence of different oxidants: hydrogen peroxide, sodium hypochlorite and new oxidative agent potassium peroxodisulfate were evaluated. Synthesized compounds have been fully characterized by FTIR, 1H and 13C NMR and MS data, elemental analysis and purity have been determined by gas chromatographic method (GC. According to our knowledge, ten synthesized thioncarbamates are for the first time characterized. Synthesized compounds could be used as selective reagents for flotation of copper and zinc ores. The presented methods offer several benefits, namely, high product yields and purity, simple operation, mild reaction conditions without use of hazardous organic solvents, while some of them could be implemented on industrial scale production.

Atmospheric chemistry of CH3O(CF2CF2O)(n)CH3 (n=1-3): Kinetics and mechanism of oxidation initiated by Cl atoms and OH radicals, IR spectra, and global warmin potentials

DEFF Research Database (Denmark)

Andersen, Mads Peter Sulbæk; Hurley, MD; Wallington, TJ

2004-01-01

Smog chambers equipped with FTIR spectrometers were used to study the Cl atom and OH radical initiated oxidation of CH3O(CF2CF2O)(n)CH3 (n = 1-3) in 720 +/- 20 Torr of air at 296 +/- 3 K. Relative rate techniques were used to measure k(Cl + CH3O(CF2CF2O)(n)CH3) (3.7 +/- 10.7) x 10(-13) and k......(OH + CH3O(CF2CF2O)(n)CH3) = (2.9 +/- 0.5) x 10(-11) cm(3) molecule(-1) s(-1) leading to an estimated atmospheric lifetime of 2 years for CH3O(CF2CF2O),CH3. The Cl initiated oxidation of CH3O(CF2CF2O),CH3 in air diluent gives CH3O(CF2CF2O)(n)C(O)H in a yield which is indistinguishable from 100 Further...... oxidation leads to the diformate, H(O)CO(CF2CF2O)(n)C(O)H. A rate constant of k(Cl + CH3O(CF2CF2O)(n)CHO) = (1.81 +/- 0.36) x 10(-13) cm(3) molecule(-1) s-1 was determined. Quantitative infrared spectra for CH3O(CF2CF2O)(n)CH3 (n = 1-3) were recorded and used to estimate halocarbon global warming potentials...

High Resolution Measurements of Nitrous Oxide (N2O in the Elbe Estuary

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Lisa Brase

2017-05-01

Full Text Available Nitrous oxide (N2O is one of the most important greenhouse gases and a major sink for stratospheric ozone. Estuaries are sites of intense biological production and N2O emissions. We aimed to identify hot spots of N2O production and potential pathways contributing to N2O concentrations in the surface water of the tidal Elbe estuary. During two research cruises in April and June 2015, surface water N2O concentrations were measured along the salinity gradient of the Elbe estuary by using a laser-based on-line analyzer coupled to an equilibrator. Based on these high-resolution N2O profiles, N2O saturations, and fluxes across the surface water/atmosphere interface were calculated. Additional measurements of DIN concentrations, oxygen concentration, and salinity were performed. Highest N2O concentrations were determined in the Hamburg port region reaching maximum values of 32.3 nM in April 2015 and 52.2 nM in June 2015. These results identify the Hamburg port region as a significant hot spot of N2O production, where linear correlations of AOU-N2Oxs indicate nitrification as an important contributor to N2O production in the freshwater part. However, in the region with lowest oxygen saturation, sediment denitrification obviously affected water column N2O saturation. The average N2O saturation over the entire estuary was 201% (SD: ±94%, with an average estuarine N2O flux density of 48 μmol m−2 d−1 and an overall emission of 0.18 Gg N2O y−1. In comparison to previous studies, our data indicate that N2O production pathways over the whole estuarine freshwater part have changed from predominant denitrification in the 1980s toward significant production from nitrification in the present estuary. Despite a significant reduction in N2O saturation compared to the 1980s, N2O concentrations nowadays remain on a high level, comparable to the mid-90s, although a steady decrease of DIN inputs occurred over the last decades. Hence, the Elbe estuary still

Mathematical modeling of nitrous oxide (N2O) emissions from full-scale wastewater treatment plants.

Science.gov (United States)

Ni, Bing-Jie; Ye, Liu; Law, Yingyu; Byers, Craig; Yuan, Zhiguo

2013-07-16

Mathematical modeling of N2O emissions is of great importance toward understanding the whole environmental impact of wastewater treatment systems. However, information on modeling of N2O emissions from full-scale wastewater treatment plants (WWTP) is still sparse. In this work, a mathematical model based on currently known or hypothesized metabolic pathways for N2O productions by heterotrophic denitrifiers and ammonia-oxidizing bacteria (AOB) is developed and calibrated to describe the N2O emissions from full-scale WWTPs. The model described well the dynamic ammonium, nitrite, nitrate, dissolved oxygen (DO) and N2O data collected from both an open oxidation ditch (OD) system with surface aerators and a sequencing batch reactor (SBR) system with bubbling aeration. The obtained kinetic parameters for N2O production are found to be reasonable as the 95% confidence regions of the estimates are all small with mean values approximately at the center. The model is further validated with independent data sets collected from the same two WWTPs. This is the first time that mathematical modeling of N2O emissions is conducted successfully for full-scale WWTPs. While clearly showing that the NH2OH related pathways could well explain N2O production and emission in the two full-scale plants studied, the modeling results do not prove the dominance of the NH2OH pathways in these plants, nor rule out the possibility of AOB denitrification being a potentially dominating pathway in other WWTPs that are designed or operated differently.

Photocatalytic oxidation of propylene on La and N codoped TiO{sub 2} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Liu, Jinfeng; Li, Haiyan; Zong, Lanlan; Li, Qiuye, E-mail: lqybys@163.com; Wang, Xiaodong; Zhang, Min; Yang, Jianjun, E-mail: yangjianjun@henu.edu.cn [Henan University, Key Laboratory for Special Functional Materials (China)

2015-02-15

Lanthanum- and nitrogen-codoped TiO{sub 2} photocatalysts was synthesized using orthorhombic nanotubes titanic acid as the precursor by a simple impregnation and subsequent calcination method. The morphology, phase structure, and properties of La- and N-codoped TiO{sub 2} were well characterized by transmission electron microscopy, X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, and UV–Vis diffuse reflectance spectra. The La-/N-codoped TiO{sub 2} showed excellent photoactivity of propylene oxidation compared with the single-doped TiO{sub 2} and La-/N-codoped P25 TiO{sub 2} nanoparticles under visible light irradiation. The origin of the enhancement of the visible light-responsive photocatalytic activity was discussed in detail.

Ethanol oxidation reactions catalyzed by water molecules: CH3CH2OH+n H2O→ CH3CHO+ H2+n H2O (n=0,1,2)

Science.gov (United States)

Takahashi, H.; Hisaoka, S.; Nitta, T.

2002-09-01

Ab initio density functional theory calculations have been performed to investigate the catalytic role of water molecules in the oxidation reaction of ethanol: CH3CH2OH+n H2O→ CH3CHO+ H2+n H2O (n=0,1,2) . The results show that the potential energy barrier for the reaction is 88.0 kcal/mol in case of n=0, while it is reduced by ˜34 kcal/mol when two water molecules are involved ( n=2) in the reaction. As a result, the rate constant increases to 3.31×10 -4 s-1, which shows a significant catalytic role of water molecules in the ethanol oxidation reactions.

Cu2O-based solar cells using oxide semiconductors

Science.gov (United States)

Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

2016-01-01

We describe significant improvements of the photovoltaic properties that were achieved in Al-doped ZnO (AZO)/n-type oxide semiconductor/p-type Cu2O heterojunction solar cells fabricated using p-type Cu2O sheets prepared by thermally oxidizing Cu sheets. The multicomponent oxide thin film used as the n-type semiconductor layer was prepared with various chemical compositions on non-intentionally heated Cu2O sheets under various deposition conditions using a pulsed laser deposition method. In Cu2O-based heterojunction solar cells fabricated using various ternary compounds as the n-type oxide thin-film layer, the best photovoltaic performance was obtained with an n-ZnGa2O4 thin-film layer. In most of the Cu2O-based heterojunction solar cells using multicomponent oxides composed of combinations of various binary compounds, the obtained photovoltaic properties changed gradually as the chemical composition was varied. However, with the ZnO-MgO and Ga2O3-Al2O3 systems, higher conversion efficiencies (η) as well as a high open circuit voltage (Voc) were obtained by using a relatively small amount of MgO or Al2O3, e.g., (ZnO)0.91-(MgO)0.09 and (Ga2O3)0.975-(Al2O3)0.025, respectively. When Cu2O-based heterojunction solar cells were fabricated using Al2O3-Ga2O3-MgO-ZnO (AGMZO) multicomponent oxide thin films deposited with metal atomic ratios of 10, 60, 10 and 20 at.% for the Al, Ga, Mg and Zn, respectively, a high Voc of 0.98 V and an η of 4.82% were obtained. In addition, an enhanced η and an improved fill factor could be achieved in AZO/n-type multicomponent oxide/p-type Cu2O heterojunction solar cells fabricated using Na-doped Cu2O (Cu2O:Na) sheets that featured a resistivity controlled by optimizing the post-annealing temperature and duration. Consequently, an η of 6.25% and a Voc of 0.84 V were obtained in a MgF2/AZO/n-(Ga2O3-Al2O3)/p-Cu2O:Na heterojunction solar cell fabricated using a Cu2O:Na sheet with a resistivity of approximately 10 Ω·cm and a (Ga0.975Al0.025)2

Cu2O-based solar cells using oxide semiconductors

International Nuclear Information System (INIS)

Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

2016-01-01

We describe significant improvements of the photovoltaic properties that were achieved in Al-doped ZnO (AZO)/n-type oxide semiconductor/p-type Cu 2 O heterojunction solar cells fabricated using p-type Cu 2 O sheets prepared by thermally oxidizing Cu sheets. The multicomponent oxide thin film used as the n-type semiconductor layer was prepared with various chemical compositions on non-intentionally heated Cu 2 O sheets under various deposition conditions using a pulsed laser deposition method. In Cu 2 O-based heterojunction solar cells fabricated using various ternary compounds as the n-type oxide thin-film layer, the best photovoltaic performance was obtained with an n-ZnGa 2 O 4 thin-film layer. In most of the Cu 2 O-based heterojunction solar cells using multicomponent oxides composed of combinations of various binary compounds, the obtained photovoltaic properties changed gradually as the chemical composition was varied. However, with the ZnO-MgO and Ga 2 O 3 -Al 2 O 3 systems, higher conversion efficiencies (η) as well as a high open circuit voltage (V oc ) were obtained by using a relatively small amount of MgO or Al 2 O 3 , e.g., (ZnO) 0.91 –(MgO) 0.09 and (Ga 2 O 3 ) 0.975 –(Al 2 O 3 ) 0.025 , respectively. When Cu 2 O-based heterojunction solar cells were fabricated using Al 2 O 3 –Ga 2 O 3 –MgO–ZnO (AGMZO) multicomponent oxide thin films deposited with metal atomic ratios of 10, 60, 10 and 20 at.% for the Al, Ga, Mg and Zn, respectively, a high V oc of 0.98 V and an η of 4.82% were obtained. In addition, an enhanced η and an improved fill factor could be achieved in AZO/n-type multicomponent oxide/p-type Cu 2 O heterojunction solar cells fabricated using Na-doped Cu 2 O (Cu 2 O:Na) sheets that featured a resistivity controlled by optimizing the post-annealing temperature and duration. Consequently, an η of 6.25% and a V oc of 0.84 V were obtained in a MgF 2 /AZO/n-(Ga 2 O 3 –Al 2 O 3 )/p-Cu 2 O:Na heterojunction solar cell fabricated using

A consilience model to describe N2O production during biological N removal

DEFF Research Database (Denmark)

Domingo Felez, Carlos; Smets, Barth F.

2016-01-01

Nitrous oxide (N2O), a potent greenhouse gas, is produced during biological nitrogen conversion in wastewater treatment operations. Complex mechanisms underlie N2O production by autotrophic and heterotrophic organisms, which continue to be unravelled. Mathematical models that describe nitric oxide...... (NO) and N2O dynamics have been proposed. Here, a first comprehensive model that considers all relevant NO and N2O production and consumption mechanisms is proposed. The model describes autotrophic NO production by ammonia oxidizing bacteria associated with ammonia oxidation and with nitrite reduction......, followed by NO reduction to N2O. It also considers NO and N2O as intermediates in heterotrophic denitrification in a 4-step model. Three biological NO and N2O production pathways are accounted for, improving the capabilities of existing models while not increasing their complexity. Abiotic contributions...

Impacts of oxidants in atomic layer deposition method on Al2O3/GaN interface properties

Science.gov (United States)

Taoka, Noriyuki; Kubo, Toshiharu; Yamada, Toshikazu; Egawa, Takashi; Shimizu, Mitsuaki

2018-01-01

The electrical interface properties of GaN metal-oxide-semiconductor (MOS) capacitors with an Al2O3 gate insulator formed by atomic layer deposition method using three kinds of oxidants were investigated by the capacitance-voltage technique, Terman method, and conductance method. We found that O3 and the alternate supply of H2O and O3 (AS-HO) are effective for reducing the interface trap density (D it) at the energy range of 0.15 to 0.30 eV taking from the conduction band minimum. On the other hand, we found that surface potential fluctuation (σs) induced by interface charges for the AS-HO oxidant is much larger than that for a Si MOS capacitor with a SiO2 layer formed by chemical vapor deposition despite the small D it values for the AS-HO oxidant compared with the Si MOS capacitor. This means that the total charged center density including the fixed charge density, charged slow trap density, and charged interface trap density for the GaN MOS capacitor is higher than that for the Si MOS capacitor. Therefore, σs has to be reduced to improve the performances and reliability of GaN devices with the Al2O3/GaN interfaces.

Removal of Hazardous Pollutants from Wastewaters: Applications of TiO2-SiO2 Mixed Oxide Materials

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Shivatharsiny Rasalingam

2014-01-01

Full Text Available The direct release of untreated wastewaters from various industries and households results in the release of toxic pollutants to the aquatic environment. Advanced oxidation processes (AOP have gained wide attention owing to the prospect of complete mineralization of nonbiodegradable organic substances to environmentally innocuous products by chemical oxidation. In particular, heterogeneous photocatalysis has been demonstrated to have tremendous promise in water purification and treatment of several pollutant materials that include naturally occurring toxins, pesticides, and other deleterious contaminants. In this work, we have reviewed the different removal techniques that have been employed for water purification. In particular, the application of TiO2-SiO2 binary mixed oxide materials for wastewater treatment is explained herein, and it is evident from the literature survey that these mixed oxide materials have enhanced abilities to remove a wide variety of pollutants.

Effect of N fertilization and tillage on nitrous oxide (N2O) loss from soil under wheat production

Science.gov (United States)

Bansal, Sheel; Aberle, Ezra; Teboh, Jasper; Yuja, Szilvia; Liebig, Mark; Meier, Jacob; Boyd, Alec

2017-01-01

Nitrous oxide (N2O-N) is one of the most important gases in the atmosphere because it is 300 times more powerful than carbon dioxide in its ability to trap heat, and is a key chemical agent of ozone depletion. The amount of N2O-N emitted from agricultural fields can be quite high, depending on the complex interplay between N fertility and residue management, plant N uptake, microbial processes, environmental conditions, and wet-up and dry-down events. High N fertilizer rates generally increase yields, but may disproportionately increase N2O-N losses due to prolonged residence time in soil when not used by the crop, and incomplete decomposition of excess N-compounds by microbes. Tillage could also affect N2O-N losses through changes in soil moisture content. Though nitrogen monoxide (NO) is one form of N lost from the soil, especially under conventional tillage, this study objective was to quantify N2O loss in wheat fields from applied urea on soil under no-till (NT) versus incorporated urea under conventional till (CT).

High-Performance Asymmetric Supercapacitors of MnCo2O4 Nanofibers and N-Doped Reduced Graphene Oxide Aerogel.

Science.gov (United States)

Pettong, Tanut; Iamprasertkun, Pawin; Krittayavathananon, Atiweena; Sukha, Phansiri; Sirisinudomkit, Pichamon; Seubsai, Anusorn; Chareonpanich, Metta; Kongkachuichay, Paisan; Limtrakul, Jumras; Sawangphruk, Montree

2016-12-14

The working potential of symmetric supercapacitors is not so wide because one type of material used for the supercapacitor electrodes prefers either positive or negative charge to both charges. To address this problem, a novel asymmetrical supercapacitor (ASC) of battery-type MnCo 2 O 4 nanofibers (NFs)//N-doped reduced graphene oxide aerogel (N-rGO AE ) was fabricated in this work. The MnCo 2 O 4 NFs at the positive electrode store the negative charges, i.e., solvated OH - , while the N-rGO AE at the negative electrode stores the positive charges, i.e., solvated K + . An as-fabricated aqueous-based MnCo 2 O 4 //N-rGO AE ASC device can provide a wide operating potential of 1.8 V and high energy density and power density at 54 W h kg -1 and 9851 W kg -1 , respectively, with 85.2% capacity retention over 3000 cycles. To understand the charge storage reaction mechanism of the MnCo 2 O 4 , the synchrotron-based X-ray absorption spectroscopy (XAS) technique was also used to determine the oxidation states of Co and Mn at the MnCo 2 O 4 electrode after being electrochemically tested. The oxidation number of Co is oxidized from +2.76 to +2.85 after charging and reduced back to +2.75 after discharging. On the other hand, the oxidation state of Mn is reduced from +3.62 to +3.44 after charging and oxidized to +3.58 after discharging. Understanding in the oxidation states of Co and Mn at the MnCo 2 O 4 electrode here leads to the awareness of the uncertain charge storage mechanism of the spinel-type oxide materials. High-performance ASC here in this work may be practically used in high-power applications.

Synthesis, structure, and catalytic performance in cyclooctene epoxidation of a molybdenum oxide/bipyridine hybrid material: {[MoO3(bipy)][MoO3(H2O)]}n.

Science.gov (United States)

Abrantes, Marta; Amarante, Tatiana R; Antunes, Margarida M; Gago, Sandra; Paz, Filipe A Almeida; Margiolaki, Irene; Rodrigues, Alírio E; Pillinger, Martyn; Valente, Anabela A; Gonçalves, Isabel S

2010-08-02

The reaction of [MoO(2)Cl(2)(bipy)] (1) (bipy = 2,2'-bipyridine) with water in a Teflon-lined stainless steel autoclave (100 degrees C, 19 h), in an open reflux system with oil bath heating (12 h) or in a microwave synthesis system (120 degrees C, 4 h), gave the molybdenum oxide/bipyridine hybrid material {[MoO(3)(bipy)][MoO(3)(H(2)O)]}(n) (2) as a microcrystalline powder in yields of 72-92%. The crystal structure of 2 determined from synchrotron X-ray powder diffraction data is composed of two distinct neutral one-dimensional polymers: an organic-inorganic polymer, [MoO(3)(bipy)](n), and a purely inorganic chain, [MoO(3)(H(2)O)](n), which are interconnected by O-H...O hydrogen bonding interactions. Compound 2 is a moderately active, stable, and selective catalyst for the epoxidation of cis-cyclooctene at 55 degrees C with tert-butylhydroperoxide (tBuOOH, 5.5 M in decane or 70% aqueous) as the oxidant. Biphasic solid-liquid or triphasic solid-organic-aqueous mixtures are formed, and 1,2-epoxycyclooctane is the only reaction product. When n-hexane is employed as a cosolvent and tBuOOH(decane) is the oxidant, the catalytic reaction is heterogeneous in nature, and the solid catalyst can be recycled and reused without a loss of activity. For comparison, the catalytic performance of the precursor 1 was also investigated. The IR spectra of solids recovered after catalysis indicate that 1 transforms into the organic-inorganic polymer [MoO(3)(bipy)] when the oxidant is tBuOOH(decane) and compound 2 when the oxidant is 70% aqueous tBuOOH.

Aircraft Observations of Nitrous Oxide (N2O) in the San Joaquin Valley of California

Science.gov (United States)

Muto, S.; Herrera, S.; Pusede, S.

2017-12-01

Agriculture is the largest source of anthropogenic nitrous oxide (N2O) in the U.S. While it is generally known which processes produce N2O, there is considerable uncertainty in controls over N2O emissions. Factors that determine N2O fluxes, such as soil properties and manure management, are highly variable in space and time, and, as a result, it has proven difficult to upscale chamber-derived soil flux measurements to regional spatial scales. Aircraft observations provide a regional picture of the N2O spatial distribution, but, because N2O is very long-lived, it is challenging to attribute measured concentrations of N2O to distinct local sources, especially over areas with complex and integrated land use. This study takes advantage of a novel aircraft N2O dataset collected onboard the low-flying, slow-moving NASA C-23 Sherpa in the San Joaquin Valley (SJV) of California, a region with a variety of N2O sources, including dairies, feedlots, fertilized cropland, and industrial facilities. With these measurements, we link observed N2O enhancements to specific sources at sub-inventory spatial scales. We compare our results with area-weighted emission profiles obtained by integrating detailed emission inventory data, agricultural statistics, and GIS source mapping.

Promoting mechanism of N-doped single-walled carbon nanotubes for O2 dissociation and SO2 oxidation

Science.gov (United States)

Chen, Yanqiu; Yin, Shi; Chen, Yang; Cen, Wanglai; Li, Jianjun; Yin, Huaqiang

2018-03-01

Although heteroatom doping in carbon based catalysts have recently received intensive attentions, the role of the intrinsically porous structure of practical carbon materials and their potential synergy with doping atoms are still unclear. To investigate the complex effects, a range of N-doped single-walled carbon nanotubes (SWCNTs) were used to investigate their potential use for O2 dissociation and the subsequent SO2 oxidation using density functional theory. It is found that graphite N doping can synergize with the outer surface of SWCNTs to facilitate the dissociation of O2. The barrier for the dissociation on dual graphite N-doped SWCNT-(8, 8) is as low as 0.3 eV, and the subsequent SO2 oxidation is thermodynamically favorable and kinetically feasible. These results spotlight on developing promising carboncatalyst via utilization of porous gemometry and heteroatom-doping of carbon materials simultaneously.

Self-aligned indium–gallium–zinc oxide thin-film transistors with SiN{sub x}/SiO{sub 2}/SiN{sub x}/SiO{sub 2} passivation layers

Energy Technology Data Exchange (ETDEWEB)

Chen, Rongsheng, E-mail: rschen@ust.hk; Zhou, Wei; Zhang, Meng; Kwok, Hoi-Sing

2014-08-01

Self-aligned top-gate amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) with SiN{sub x}/SiO{sub 2}/SiN{sub x}/SiO{sub 2} passivation layers are developed in this paper. The resulting a-IGZO TFT exhibits high reliability against bias stress and good electrical performance including field-effect mobility of 5 cm{sup 2}/Vs, threshold voltage of 2.5 V, subthreshold swing of 0.63 V/decade, and on/off current ratio of 5 × 10{sup 6}. With scaling down of the channel length, good characteristics are also obtained with a small shift of the threshold voltage and no degradation of subthreshold swing. The proposed a-IGZO TFTs in this paper can act as driving devices in the next generation flat panel displays. - Highlights: • Self-aligned top-gate indium–gallium–zinc oxide thin-film transistor is proposed. • SiN{sub x}/SiO{sub 2}/SiN{sub x}/SiO{sub 2} passivation layers are developed. • The source/drain areas are hydrogen-doped by CHF3 plasma. • The devices show good electrical performance and high reliability against bias stress.

p-Cu2O-shell/n-TiO2-nanowire-core heterostucture photodiodes

Directory of Open Access Journals (Sweden)

Hsueh Ting-Jen

2011-01-01

Full Text Available Abstract This study reports the deposition of cuprous oxide [Cu2O] onto titanium dioxide [TiO2] nanowires [NWs] prepared on TiO2/glass templates. The average length and average diameter of these thermally oxidized and evaporated TiO2 NWs are 0.1 to 0.4 μm and 30 to 100 nm, respectively. The deposited Cu2O fills gaps between the TiO2 NWs with good step coverage to form nanoshells surrounding the TiO2 cores. The p-Cu2O/n-TiO2 NW heterostructure exhibits a rectifying behavior with a sharp turn-on at approximately 0.9 V. Furthermore, the fabricated p-Cu2O-shell/n-TiO2-nanowire-core photodiodes exhibit reasonably large photocurrent-to-dark-current contrast ratios and fast responses.

Upland Trees Contribute to Exchange of Nitrous Oxide (N2O) in Forest Ecosystems

Science.gov (United States)

Tian, H.; Thompson, R.; Canadell, J.; Winiwarter, W.; Machacova, K.; Maier, M.; Halmeenmäki, E.; Svobodova, K.; Lang, F.; Pihlatie, M.; Urban, O.

2017-12-01

The increase in atmospheric nitrous oxide (N2O) concentration contributes to the acceleration of the greenhouse effect. However, the role of trees in the N2O exchange of forest ecosystems is still an open question. While the soils of temperate and boreal forests were shown to be a natural source of N2O, trees have been so far overlooked in the forest N2O inventories. We determined N2O fluxes in common tree species of boreal and temperate forests: Scots pine (Pinus sylvestris), Norway spruce (Picea abies), downy and silver birch (Betula pubescens, B. pendula), and European beech (Fagus sylvatica). We investigated (1) whether these tree species exchange N2O with the atmosphere under natural field conditions, (2) how the tree N2O fluxes contribute to the forest N2O balance, and (3) whether these fluxes show seasonal dynamics. The studies were performed in a boreal forest (SMEAR II station, Finland; June 2014 - May 2015) and two temperate mountain forests (White Carpathians, Czech Republic; Black Forest, Germany; June and July 2015). Fluxes of N2O in mature tree stems and forest floor were measured using static chamber systems followed by chromatographic and photo-acoustic analyses of N2O concentration changes. Pine, spruce and birch trees were identified as net annual N2O sources. Spruce was found the strongest emitter (0.27 mg ha-1 h-1) amounting thus up to 2.5% of forest floor N2O emissions. All tree species showed a substantial seasonality in stem N2O flux that was related to their physiological activity and climatic variables. In contrast, stems of beech trees growing at soils consuming N2O may act as a substantial sink of N2O from the atmosphere. Consistent N2O consumption by tree stems ranging between -12.1 and -35.2 mg ha-1 h-1 and contributing by up to 3.4% to the forest floor N2O uptake is a novel finding in contrast to current studies presenting trees as N2O emitters. To understand these fluxes, N2O exchange of photoautotrophic organisms associated with

Nitrous Oxide (N2O production in axenic Chlorella vulgaris microalgae cultures: evidence, putative pathways, and potential environmental impacts

Directory of Open Access Journals (Sweden)

B. Guieysse

2013-10-01

Full Text Available Using antibiotic assays and genomic analysis, this study demonstrates nitrous oxide (N2O is generated from axenic Chlorella vulgaris cultures. In batch assays, this production is magnified under conditions favouring intracellular nitrite accumulation, but repressed when nitrate reductase (NR activity is inhibited. These observations suggest N2O formation in C. vulgaris might proceed via NR-mediated nitrite reduction into nitric oxide (NO acting as N2O precursor via a pathway similar to N2O formation in bacterial denitrifiers, although NO reduction to N2O under oxia remains unproven in plant cells. Alternatively, NR may reduce nitrite to nitroxyl (HNO, the latter being known to dimerize to N2O under oxia. Regardless of the precursor considered, an NR-mediated nitrite reduction pathway provides a unifying explanation for correlations reported between N2O emissions from algae-based ecosystems and NR activity, nitrate concentration, nitrite concentration, and photosynthesis repression. Moreover, these results indicate microalgae-mediated N2O formation might significantly contribute to N2O emissions in algae-based ecosystems (e.g. 1.38–10.1 kg N2O-N ha−1 yr−1 in a 0.25 m deep raceway pond operated under Mediterranean climatic conditions. These findings have profound implications for the life cycle analysis of algae biotechnologies and our understanding of the global biogeochemical nitrogen cycle.

Tidal and spatial variability of nitrous oxide (N2O) in Sado estuary (Portugal)

Science.gov (United States)

Gonçalves, Célia; Brogueira, Maria José; Nogueira, Marta

2015-12-01

The estimate of the nitrous oxide (N2O) fluxes is fundamental to assess its impact on global warming. The tidal and spatial variability of N2O and the air-sea fluxes in the Sado estuary in July/August 2007 are examined. Measurements of N2O and other relevant environmental parameters (temperature, salinity, dissolved oxygen and dissolved inorganic nitrogen - nitrate plus nitrite and ammonium) were recorded during two diurnal tidal cycles performed in the Bay and Marateca region and along the estuary during ebb, at spring tide. N2O presented tidal and spatial variability and varied spatially from 5.0 nmol L-1 in Marateca region to 12.5 nmol L-1 in Sado river input. Although the Sado river may constitute a considerable N2O source to the estuary, the respective chemical signal discharge was rapidly lost in the main body of the estuary due to the low river flow during the sampling period. N2O varied with tide similarly between 5.2 nmol L-1 (Marateca) and 10.0 nmol L-1 (Sado Bay), with the maximum value reached two hours after flooding period. The influence of N2O enriched upwelled seawater (˜10.0 nmol L-1) was well visible in the estuary mouth and apparently represented an important contribution of N2O in the main body of Sado estuary. Despite the high water column oxygen saturation in most of Sado estuary, nitrification did not seem a relevant process for N2O production, probably as the concentration of the substrate, NH4+, was not adequate for this process to occur. Most of the estuary functioned as a N2O source, and only Marateca zone has acted as N2O sink. The N2O emission from Sado estuary was estimated to be 3.7 Mg N-N2O yr-1 (FC96) (4.4 Mg N-N2O yr-1, FRC01). These results have implications for future sampling and scaling strategies for estimating greenhouse gases (GHGs) fluxes in tidal ecosystems.

Cobalt Oxide Catalysts on Commercial Supports for N2O Decomposition.

Czech Academy of Sciences Publication Activity Database

Klegová, A.; Pacultová, K.; Fridrichová, D.; Volodarskaja, A.; Kovanda, J.; Jirátová, Květa

2017-01-01

Roč. 40, č. 5 (2017), s. 981-990 ISSN 0930-7516. [International Congress of Chemical and Process Engineering CHISA 2016 /22./ and the 19th Conference PRES 2016. Prague, 27.08.2016-31.08.2016] R&D Projects: GA ČR GA14-13750S Institutional support: RVO:67985858 Keywords : N2O decomposition * cobalt oxide * shaped catalyst Subject RIV: CI - Industrial Chemistry, Chemical Engineering OBOR OECD: Chemical process engineering Impact factor: 2.051, year: 2016

Studies on nitrogen oxides (NO{sub x} and N{sub 2}O) in pressurized fluidized bed combustion

Energy Technology Data Exchange (ETDEWEB)

Lu Yong

1998-09-01

This thesis describes the experimental studies of nitrogen oxide (NO, NO{sub 2}, N{sub 2}O) emissions in pressurized fluidized bed combustion (PFBC). In the first part of the thesis the background and the objectives of this study are introduced. The second part summarizes the fundamental knowledge about the formation and destruction of nitrogen oxides in coal combustion, particularly in the conditions of PFBC. The instrumentation of test facilities, measurement and data analysis is described in the third part. Then the most important experimental results follow in the next parts. The forth part describes the results from a PFBC test rig and an empirical modelling for predicting the emissions of NO{sub x} and N{sub 2}O. Finally, the fundamental work on coal combustion and fuel nitrogen conversion in a PFBC batch reactor is presented. These studies clearly confirm the potential of PFBC technology in the control nitrogen of oxide emissions. The research in the test rig was concentrated on determining the effects of process parameters on the emissions of nitrogen oxides with different fuels. Another objective was to examine the reduction of nitrogen oxides with the control methods in PFBC conditions, including ammonia injection and air staging combustion for reducing NO, and high temperature operations for reducing N{sub 2}0. The results indicate that pressurized operation suppresses the conversion of fuel-N to nitrogen oxides and favors with employing the reduction methods for further nitrogen oxide reduction, for instance the temperature window of NO reduction with ammonia injection has been found to be widened to even lower temperature range. Maximum reductions of 80-85 % with ammonia injection and 75-80 % with air staging combustion were achieved in the conditions examined. Considerably low emissions of N{sub 2}O (<7 ppm) were obtained in the tests of N{sub 2}O control, and thermal decomposition proved to be the laming pathway of N{sub 2}O destruction in PFBC. In

Binary Oxide p-n Heterojunction Piezoelectric Nanogenerators with an Electrochemically Deposited High p-Type Cu2O Layer.

Science.gov (United States)

Baek, Seung Ki; Kwak, Sung Soo; Kim, Joo Sung; Kim, Sang Woo; Cho, Hyung Koun

2016-08-31

The high performance of ZnO-based piezoelectric nanogenerators (NGs) has been limited due to the potential screening from intrinsic electron carriers in ZnO. We have demonstrated a novel approach to greatly improve piezoelectric power generation by electrodepositing a high-quality p-type Cu2O layer between the piezoelectric semiconducting film and the metal electrode. The p-n heterojunction using only oxides suppresses the screening effect by forming an intrinsic depletion region, and thus sufficiently enhances the piezoelectric potential, compared to the pristine ZnO piezoelectric NG. Interestingly, a Sb-doped Cu2O layer has high mobility and low surface trap states. Thus, this doped layer is an attractive p-type material to significantly improve piezoelectric performance. Our results revealed that p-n junction NGs consisting of Au/ZnO/Cu2O/indium tin oxide with a Cu2O:Sb (cuprous oxide with a small amount of antimony) layer of sufficient thickness (3 μm) exhibit an extraordinarily high piezoelectric potential of 0.9 V and a maximum output current density of 3.1 μA/cm(2).

Controlling factors of nitrous oxide (N2O) emissions at the field-scale in an agricultural slope

Science.gov (United States)

Vilain, Guillaume; Garnier, Josette; Tallec, Gaëlle; Tournebize, Julien; Cellier, Pierre; Flipo, Nicolas

2010-05-01

Agricultural practices widely contribute to the atmospheric nitrous oxide (N2O) concentration increase and are the major source of N2O which account for 24% of the global annual emission (IPCC, 2007). Soil nitrification and denitrification are the microbial processes responsible for the production of N2O, which also depends on soil characteristics and management. Besides their control by various factors, such as climate, soil conditions and management (content of NO3- and NH4+, soil water content, presence of degradable organic material…), the role of topography is less known although it can play an important role on N2O emissions (Izaurralde et al., 2004). Due to the scarcity of data on N2O direct vs. indirect emission rate from agriculture in the Seine Basin (Garnier et al., 2009), one of the objectives of the study conducted here was to determine the N2O emission rates of the various land use representative for the Seine Basin, in order to better assess the direct N2O emissions, and to explore controlling factor such as meteorology, topography, soil properties and crop successions. The main objective of this study was at the same time to characterize N2O fluxes variability along a transect from an agricultural plateau to a river and to analyze the influence of landscape position on these emissions. We conducted this study in the Orgeval catchment (Seine basin, France; between 48°47' and 48°55' N, and 03°00' and 03°55' E) from May 2008 to August 2009 on two agricultural fields cropped with wheat, barley, oats, corn. N2O fluxes were monitored from weekly to bimonthly using static manual chambers placed along the chosen transect in five different landscape positions from the plateau to the River. This study has shown that soil moisture (expressed as Water Filled Pore Space) and NO3- soil concentrations explained most of the N2O flux variability during the sampling period. Most of N2O was emitted directly after N fertilization application during a relatively

Al- or Si-decorated graphene oxide: A favorable metal-free catalyst for the N2O reduction

International Nuclear Information System (INIS)

Esrafili, Mehdi D.; Sharifi, Fahimeh; Nematollahi, Parisa

2016-01-01

Highlights: • The reduction of N 2 O by CO molecule is investigated over Al- and Si-decorated graphene oxides (Al-/Si-GO). • The N 2 O decomposition process can take place with a negligible activation energy over both surfaces. • Al-GO and Si-GO can be used as an efficient metal-free catalyst for the reduction of N 2 O molecule at ambient conditions. - Abstract: The structural and catalytic properties of Al- or Si-decorated graphene oxide (Al-/Si-GO) are studied by means of density functional theory calculations. The relatively large adsorption energy together with the small Al−O or Si−O binding distances indicate that the epoxy groups over the GO surface can strongly stabilize the single Al or Si atom. Hence, Al-GO and Si-GO are stable enough to be utilized in catalytic reduction of N 2 O by CO molecule. It is found that the adsorption and decomposition of N 2 O molecule over Si-GO is more favorable than over Al-GO, due to its larger adsorption energy (E ads ) and charge transfer (q CT ) values. On the other hand, the CO molecule is physically adsorbed over both surfaces, with relatively small E ads and q CT values. Therefore, at the presence of N 2 O and CO molecules as the reaction gas, the Al or Si atom of the surface should be dominantly covered by N 2 O molecule. Our results indicate that the N 2 O decomposition process can take place with a negligible activation energy over Al-/Si-GO surface, where the N 2 molecule can be easily released from the surface. Then, the activated oxygen atom (O ads ) which remains over the surface reacts with the CO molecule to form the CO 2 molecule via the reaction O ads + CO → CO 2 . Based on the calculated activation energies, it is suggested that both Al-GO and Si-GO can be used as an efficient metal-free catalyst for the reduction of N 2 O molecule at ambient conditions.

Effect of the thin Ga2O3 layer in n+-ZnO/n-Ga2O3/p-Cu2O heterojunction solar cells

International Nuclear Information System (INIS)

Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

2013-01-01

The influence of inserting a Ga 2 O 3 thin film as an n-type semiconductor layer on the obtainable photovoltaic properties in Cu 2 O-based heterojunction solar cells was investigated with a transparent conductive Al-doped ZnO (AZO) thin film/n-Ga 2 O 3 thin film/p-Cu 2 O sheet structure. It was found that this Ga 2 O 3 thin film can greatly improve the performance of Cu 2 O-based heterojunction solar cells fabricated using polycrystalline Cu 2 O sheets that had been prepared by a thermal oxidization of copper sheets. The obtained photovoltaic properties in the AZO/Ga 2 O 3 /Cu 2 O heterojunction solar cells were strongly dependent on the deposition conditions of the Ga 2 O 3 films. The external quantum efficiency obtained in AZO/Ga 2 O 3 /Cu 2 O heterojunction solar cells was found to be greater at wavelengths below approximately 500 nm than that obtained in AZO/Cu 2 O heterojunction solar cells (i.e., prepared without a Ga 2 O 3 layer) at equivalent wavelengths. This improvement of photovoltaic properties is mainly attributed to a decrease in the level of defects at the interface between the Ga 2 O 3 thin film and the Cu 2 O sheet. Conversion efficiencies over 5% were obtained in AZO/Ga 2 O 3 /Cu 2 O heterojunction solar cells fabricated using an n-Ga 2 O 3 thin-film layer prepared with a thickness of 40–80 nm at an O 2 gas pressure of approximately 1.7 Pa by a pulsed laser deposition. - Highlights: • We demonstrate high-efficiency Cu 2 O-based p-n heterojunction solar cells. • A non-doped Ga 2 O 3 thin film was used as an n-type semiconductor layer. • The Ga 2 O 3 thin film was prepared at a low temperature by a low damage deposition. • p-type Cu 2 O sheets prepared by thermal oxidization of copper sheets were used. • Conversion efficiencies over 5% were obtained in AZO/n-Ga 2 O 3 /p-Cu 2 O solar cells

Catalytic oxidation of volatile organic compounds (n-hexane, benzene, toluene, o-xylene promoted by cobalt catalysts supported on γ-Al2O3-CeO2

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R. Balzer

2014-09-01

Full Text Available Cobalt catalysts supported on γ-alumina, ceria and γ-alumina-ceria, with 10 or 20%wt of cobalt load, prepared by the wet impregnation method and characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, field emission transmission electron microscopy (FETEM, N2 adsorption-desorption isotherms (BET/BJH methods, energy-dispersive X-ray spectroscopy (EDX, X-ray photoemission spectroscopy (XPS, O2-chemisorption and temperature programmed reduction (TPR were used to promote the oxidation of volatile organic compounds (n-hexane, benzene, toluene and o-xylene. For a range of low temperatures (50-350 °C, the activity of the catalysts with a higher cobalt load (20% wt was greater than that of the catalysts with a lower cobalt load (10% wt. The Co/γ-Al2O3-CeO2 catalytic systems presented the best performances. The results obtained in the characterization suggest that the higher catalytic activity of the Co20/γ-Al2O3-CeO2 catalyst may be attributed to the higher metal content and amount of oxygen vacancies, as well as the effects of the interaction between the cobalt and the alumina and cerium oxides.

Improved linearity and reliability in GaN metal-oxide-semiconductor high-electron-mobility transistors using nanolaminate La2O3/SiO2 gate dielectric

Science.gov (United States)

Hsu, Ching-Hsiang; Shih, Wang-Cheng; Lin, Yueh-Chin; Hsu, Heng-Tung; Hsu, Hisang-Hua; Huang, Yu-Xiang; Lin, Tai-Wei; Wu, Chia-Hsun; Wu, Wen-Hao; Maa, Jer-Shen; Iwai, Hiroshi; Kakushima, Kuniyuki; Chang, Edward Yi

2016-04-01

Improved device performance to enable high-linearity power applications has been discussed in this study. We have compared the La2O3/SiO2 AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) with other La2O3-based (La2O3/HfO2, La2O3/CeO2 and single La2O3) MOS-HEMTs. It was found that forming lanthanum silicate films can not only improve the dielectric quality but also can improve the device characteristics. The improved gate insulation, reliability, and linearity of the 8 nm La2O3/SiO2 MOS-HEMT were demonstrated.

Catalytic Oxidation of Propene over Pd Catalysts Supported on CeO2, TiO2, Al2O3 and M/Al2O3 Oxides (M = Ce, Ti, Fe, Mn

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Sonia Gil

2015-04-01

Full Text Available In the following work, the catalytic behavior of Pd catalysts prepared using different oxides as support (Al2O3, CeO2 and TiO2 in the catalytic combustion of propene, in low concentration in excess of oxygen, to mimic the conditions of catalytic decomposition of a volatile organic compound of hydrocarbon-type is reported. In addition, the influence of different promoters (Ce, Ti, Fe and Mn when added to a Pd/Al2O3 catalyst was analyzed. Catalysts were prepared by the impregnation method and were characterized by ICP-OES, N2 adsorption, temperature-programmed reduction, temperature-programmed oxidation, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Catalyst prepared using CeO2 as the support was less easily reducible, due to the stabilization effect of CeO2 over the palladium oxides. Small PdO particles and, therefore, high Pd dispersion were observed for all of the catalysts, as confirmed by XRD and TEM. The addition of Ce to the Pd/Al2O3 catalysts increased the metal-support interaction and the formation of highly-dispersed Pd species. The addition of Ce and Fe improved the catalytic behavior of the Pd/Al2O3 catalyst; however, the addition of Mn and Ti decreased the catalytic activity in the propene oxidation. Pd/TiO2 showed the highest catalytic activity, probably due to the high capacity of this catalyst to reoxidize Pd into PdO, as has been found in the temperature-programmed oxidation (TPO experiments.

Properties of thermally oxidized and nitrided Zr-oxynitride thin film on 4H–SiC in diluted N2O ambient

International Nuclear Information System (INIS)

Wong, Yew Hoong; Cheong, Kuan Yew

2012-01-01

A systematic investigation on the structural, chemical, and electrical properties of thermally oxidized and nitrided sputtered Zr thin film in various N 2 O ambient (10–100%) at 500 °C for 15 min to form Zr-oxynitride on 4H–SiC substrate has been carried out. The chemical composition, depth profile analysis, and energy band alignment have been evaluated by X-ray photoelectron spectrometer. Zr-oxynitride layer and its interfacial layer comprised of compounds related to Zr–O, Zr–N, Zr–O–N, Si–N, and/or C–N were identified. A model related to the oxidation and nitridation mechanism has been suggested. Supportive results related to the model were obtained by energy filtered transmission electron microscopy, X-ray diffraction, and Raman analyses. A proposed crystal structure was employed to elucidate the surface roughness and topographies of the samples, which were characterized by atomic force microscopy. The electrical results revealed that 10% N 2 O sample has possessed the highest breakdown field and reliability. This was owing to the confinement of nitrogen-related compounds of Zr–O–N and/or Zr–N at or near interfacial layer region, smaller grain with finer structure on the surface, the lowest interface trap density, total interface trap density, and effective oxide charge, and highest barrier height between conduction band edge of oxide and semiconductor. -- Highlights: ► Zr-oxynitride as the gate oxide deposited on 4H–SiC substrate. ► Simultaneous oxidation and nitridation of sputtered Zr thin film on 4H–SiC using various concentrations of N 2 O gas. ► Presence of interfacial layer comprised of mixed compounds related to Zr–O, Zr–N, Zr–O–N, Si–N, and/or C–N. ► The highest electrical breakdown and highest reliability at diluted N 2 O of 10%.

Characterization of Nd{sub 2}AlO{sub 3}N and Sm{sub 2}AlO{sub 3}N oxynitrides synthesized by carbothermal reduction and nitridation

Energy Technology Data Exchange (ETDEWEB)

Chevire, Francois, E-mail: francois.chevire@univ-rennes1.fr [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , Equipe Verres et Ceramiques, Groupe Materiaux Azotes et Ceramiques, Universite de Rennes 1, 35042 Rennes Cedex (France); Pallu, Arthur; Ray, Erwan; Tessier, Franck [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , Equipe Verres et Ceramiques, Groupe Materiaux Azotes et Ceramiques, Universite de Rennes 1, 35042 Rennes Cedex (France)

2011-05-12

Research highlights: > Carbothermal reduction and nitridation leads to rare earth aluminum oxynitride starting from oxide mixture. > Absorption shifts towards visible in Nd{sub 2}AlO{sub 3}N (orange) and Sm{sub 2}AlO{sub 3}N (yellow). > Oxynitrides are stable up to 600 deg. C in air. > The so-called 'intermediate phase' phenomenon is evidenced in Sm{sub 2}AlO{sub 3}N. - Abstract: The Nd{sub 2}AlO{sub 3}N and Sm{sub 2}AlO{sub 3}N oxynitrides with the K{sub 2}NiF{sub 4}-type structure have been prepared from oxide mixture at 1250 deg. C using the carbothermal reduction and nitridation route (CRN). Optimization of the process is discussed to prevent surface oxidation of the oxynitrides during the synthesis. The absorption of Nd{sub 2}AlO{sub 3}N and Sm{sub 2}AlO{sub 3}N, orange and yellow respectively, has been characterized by diffuse reflectance as well as their thermal stability versus oxidation by thermogravimetric analyses.

Thermally Oxidized C, N Co-Doped ANATASE-TiO2 Coatings on Stainless Steel for Tribological Properties

Science.gov (United States)

Wang, Hefeng; Shu, Xuefeng; Li, Xiuyan; Tang, Bin; Lin, Naiming

2013-07-01

Ti(C, N) coatings were prepared on stainless steel (SS) substrates by plasma surface alloying technique. Carbon-nitrogen co-doped titanium dioxide (C-N-TiO2) coatings were fabricated by oxidative of the Ti(C, N) coatings in air. The prepared C-N-TiO2 coatings were characterized by SEM, XPS and XRD. Results reveal that the SS substrates were entirely shielded by the C-N-TiO2 coatings. The C-N-TiO2 coatings are anatase in structure as characterized by X-ray diffraction. The tribological behavior of the coatings was tested with ball-on-disc sliding wear and compared with substrate. Such a C-N-TiO2 coatings showed good adhesion with the substrate and tribological properties of the SS in terms of much reduced friction coefficient and increased wear resistance.

Comparative Study of Catalytic Systems T iO2 and N b2O5 Estudio catalítico comparativo de los sistemas TiO2 y Nb2O5 en la degradación de cianuro en función del tipo de oxidante

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Aida Liliana Barbosa López

2012-12-01

Full Text Available This article discusses the viability of using agents such as niobium photocatalyst in decreasing higher energy of the band gap. To do so competitively withT iO2, the presence of oxidation helpers such as H2O2 and O3 could presentsurprising results in the catalytic performance due to higher generation ofOH o radicals. Oxidation helpers are shown to assist in obtaining larger areaoxides and textural properties different from commercial niobium oxide, andenhancing its catalytic activity in free cyanide removing. The article presentsexperimental results of cyanide photodegradation of 100mg/l with Degussa P-25 T iO2 and Nb2O53H2O, using a type CPC photoreactor and sunlight as theradiation source. Taking an inclination equal to Cartagena latitude of 10,450,the results show a clear effect of pH, catalyst type and oxidation auxiliar agenton photodegradation reaction. The ion cyanide reduction of polluted effluentwas enhanced by oxidizing agent (O3 and H2O2 addition. This may suggesta greater susceptibility to free cyanide oxidation and cianate indirect oxidation due to higher hydroxyl radical generation, which was induced by H2O2or O3 presence under solar radiation. The results showed free cyanide photocatalytic oxidation percentages between 64% and 72% using Nb2O5 3H2Oand 67% and 71% using T iO2 Degussa P-25. The catalysts were characterizedstructurally by XRD, BET, Raman and FTIR, with the purpose of correlatingmorphological changes in catalytic performing.La viabilidad del uso de otros agentes fotocatalizadores como el niobio, radicaen disminuir las energías altas de la banda prohibida para hacerlo competitivofrente al TiO2, sin embargo la presencia de coayudantes de oxidación, talescomo H2O2 y O3 podrían presentar resultados sorprendentes en el desempeñocatalítico, debido a una mayor generación del radicales OH. La obtención deóxidos de mayor área y propiedades texturales diferentes al oxido de niobiocomercial, mejoran su actividad catal

Photocatalytic oxidation of aromatic amines using MnO2@g-C3N4

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U.S. Environmental Protection Agency — An efficient and direct oxidation of aromatic amines to aromatic azo-compounds has been achieved using a MnO2@g-C3N4 catalyst under visible light as a source of...

Experimental Study of the Swirling Oxidizer Flow in HTPB/N2O Hybrid Rocket Motor

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Mohammad Mahdi Heydari

2017-01-01

Full Text Available Effects of swirling oxidizer flow on the performance of a HTPB/N2O Hybrid rocket motor were studied. A hybrid propulsion laboratory has been developed, to characterize internal ballistics characteristics of swirl flow hybrid motors and to define the operating parameters, like fuel regression rate, specific impulse, and characteristics velocity and combustion efficiency. Primitive variables, like pressure, thrust, temperature, and the oxidizer mass flow rate, were logged. A modular motor with 70 mm outer diameter and variable chamber length is designed for experimental analysis. The injector module has four tangential injectors and one axial injector. Liquid nitrous oxide (N2O as an oxidizer is injected at the head of combustion chamber into the motor. The feed system uses pressurized air as the pressurant. Two sets of tests have been performed. Some tests with axial and tangential oxidizer injection and a test with axial oxidizer injection were done. The test results show that the fuel grain regression rate has been improved by applying tangential oxidizer injection at the head of the motor. Besides, it was seen that combustion efficiency of motors with the swirl flow was about 10 percent more than motors with axial flow.

Diaqua-2κ2O-bis(μ-1-oxido-2-naphthoato-1:2κ3O1,O2:O2′;2:3κ3O2:O1,O2′-bis(1-oxido-2-naphthoato-1κ1O2,O2;3κ2O1,O2-hexapyridine-1κ2N,2κ2N,3κ2N-trimanganese(II/III pyridine disolvate dihydrate

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Daqi Wang

2008-12-01

Full Text Available The title complex, [Mn3(C11H6O34(C5H5N6(H2O2]·2H2O·2C5H5N, is a trinuclear mixed oxidation state complex of overline1 symmetry. The three Mn atoms are six-coordinated in the shape of distorted octahedra, each coordinated with an O4N2 set of donor atoms, where the ligands exhibit mono- and bidentate modes. However, the coordination of the MnII ion located on the inversion centre involves water molecules at two coordination sites, whereas that of the two symmetry-related MnIII ions involves an O4N2 set of donor atoms orginating from the organic ligands. Intramolecular C—H...π interactions between neighbouring pyridine ligands stabilize this arrangement. A two-dimensional network parallel to (001 is formed by intermolecular O—H...O hydrogen bonds.

Synthesis and characterization of sodium vanadium oxide gels: the effects of water (n) and sodium (x) content on the electrochemistry of Na(x)V2O5·nH2O.

Science.gov (United States)

Lee, Chia-Ying; Marschilok, Amy C; Subramanian, Aditya; Takeuchi, Kenneth J; Takeuchi, Esther S

2011-10-28

Sodium vanadium oxide gels, Na(x)V(2)O(5)·nH(2)O, of varying sodium content (0.12 n > 0.01) and interlayer spacing were found to be inversely proportional to the sodium level (x), thus control of sodium (x) content provided a direct, chimie douce approach for control of hydration level (n) and interlayer spacing, without the need for high temperature treatment to affect dehydration. Notably, the use of high temperatures to modify hydration levels can result in crystallization and collapse of the interlayer structure, highlighting the distinct advantage of our novel chimie douce synthesis strategy. Subsequent to synthesis and characterization, results from an electrochemical study of a series of Na(x)V(2)O(5)·nH(2)O samples highlight the significant impact of interlayer water on delivered capacity of the layered materials. Specifically, the sodium vanadium oxide gels with higher sodium content and lower water content provided higher capacities in lithium based cells, where capacity delivered to 2.0 V under C/20 discharge ranged from 170 mAh/g for Na(0.12)V(2)O(5)·0.23H(2)O to 300 mAh/g for Na(0.32)V(2)O(5)·0.01H(2)O. The capacity differences were maintained as the cells were cycled. This journal is © the Owner Societies 2011

Treatment of hazardous waste landfill leachate using Fenton oxidation process

Science.gov (United States)

Singa, Pradeep Kumar; Hasnain Isa, Mohamed; Ho, Yeek-Chia; Lim, Jun-Wei

2018-03-01

The efficiency of Fenton's oxidation was assessed in this study for hazardous waste landfill leachate treatment. The two major reagents, which are generally employed in Fenton's process are H2O2 as oxidizing agent and Fe2+ as catalyst. Batch experiments were conducted to determine the effect of experimental conditions viz., reaction time, molar ratio, and Fenton reagent dosages, which are significant parameters that influence the degradation efficiencies of Fenton process were examined. It was found that under the favorable experimental conditions, maximum COD removal was 56.49%. The optimum experimental conditions were pH=3, H2O2/Fe2+ molar ratio = 3 and reaction time = 150 minutes. The optimal amount of hydrogen peroxide and iron were 0.12 mol/L and 0.04 mol/L respectively. High dosages of H2O2 and iron resulted in scavenging effects on OH• radicals and lowered degradation efficiency of organic compounds in the hazardous waste landfill leachate.

[2-(Dimethylaminoethanol-κ2N,O][2-(dimethylaminoethanolato-κ2N,O]iodidocopper(II

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Elena A. Buvaylo

2012-04-01

Full Text Available The title compound, [Cu(C4H10NOI(C4H11NO], was obtained unintentionally as the product of an attempted synthesis of a Cu/Zn mixed-metal complex using zerovalent copper, zinc(II oxide and ammonium iodide in pure 2-(dimethylaminoethanol, in air. The molecular complex has no crystallographically imposed symmetry. The coordination geometry around the metal atom is distorted square-pyramidal. The equatorial coordination around copper involves donor atoms of the bidentate chelating 2-(dimethylaminoethanol ligand and the 2-(dimethylaminoethanolate group, which are mutually trans to each other, with four approximately equal short Cu—O/N bond distances. The axial Cu—I bond is substantially elongated. Intermolecular hydrogen-bonding interactions involving the –OH group of the neutral 2-(dimethylaminoethanol ligand to the O atom of the monodeprotonated 2-(dimethylaminoethanolate group of the molecule related by the n-glide plane, as indicated by the O...O distance of 2.482 (12 Å, form chains of molecules propagating along [101].

Properties of thermally oxidized and nitrided Zr-oxynitride thin film on 4H-SiC in diluted N{sub 2}O ambient

Energy Technology Data Exchange (ETDEWEB)

Wong, Yew Hoong [Energy Efficient and Sustainable Semiconductor Research Group, School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300, Nibong Tebal, Seberang Perai Selatan, Penang (Malaysia); Cheong, Kuan Yew, E-mail: cheong@eng.usm.my [Energy Efficient and Sustainable Semiconductor Research Group, School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300, Nibong Tebal, Seberang Perai Selatan, Penang (Malaysia)

2012-10-15

A systematic investigation on the structural, chemical, and electrical properties of thermally oxidized and nitrided sputtered Zr thin film in various N{sub 2}O ambient (10-100%) at 500 Degree-Sign C for 15 min to form Zr-oxynitride on 4H-SiC substrate has been carried out. The chemical composition, depth profile analysis, and energy band alignment have been evaluated by X-ray photoelectron spectrometer. Zr-oxynitride layer and its interfacial layer comprised of compounds related to Zr-O, Zr-N, Zr-O-N, Si-N, and/or C-N were identified. A model related to the oxidation and nitridation mechanism has been suggested. Supportive results related to the model were obtained by energy filtered transmission electron microscopy, X-ray diffraction, and Raman analyses. A proposed crystal structure was employed to elucidate the surface roughness and topographies of the samples, which were characterized by atomic force microscopy. The electrical results revealed that 10% N{sub 2}O sample has possessed the highest breakdown field and reliability. This was owing to the confinement of nitrogen-related compounds of Zr-O-N and/or Zr-N at or near interfacial layer region, smaller grain with finer structure on the surface, the lowest interface trap density, total interface trap density, and effective oxide charge, and highest barrier height between conduction band edge of oxide and semiconductor. -- Highlights: Black-Right-Pointing-Pointer Zr-oxynitride as the gate oxide deposited on 4H-SiC substrate. Black-Right-Pointing-Pointer Simultaneous oxidation and nitridation of sputtered Zr thin film on 4H-SiC using various concentrations of N{sub 2}O gas. Black-Right-Pointing-Pointer Presence of interfacial layer comprised of mixed compounds related to Zr-O, Zr-N, Zr-O-N, Si-N, and/or C-N. Black-Right-Pointing-Pointer The highest electrical breakdown and highest reliability at diluted N{sub 2}O of 10%.

Isotope Effects Associated with N2O Production by Fungal and Bacterial Nitric Oxide Reductases: Implications for Enzyme Mechanisms

Science.gov (United States)

Hegg, E. L.; Yang, H.; Gandhi, H.; McQuarters, A.; Lehnert, N.; Ostrom, N. E.

2014-12-01

Nitrous oxide (N2O) is both a powerful greenhouse gas and a key participant in ozone destruction. Microbial activity accounts for over 70% of the N2O produced annually, and the atmospheric concentration of N2O continues to rise. Because the fungal and bacterial denitrification pathways are major contributors to microbial N2O production, understanding the mechanism by which NO is reduced to N2O will contribute to both N2O source tracing and quantification. Our strategy utilizes stable isotopes to probe the enzymatic mechanism of microbial N2O production. Although the use of stable isotopes to study enzyme mechanisms is not new, our approach is distinct in that we employ both measurements of isotopic preferences of purified enzyme and DFT calculations, thereby providing a synergistic combination of experimental and computational approaches. We analyzed δ18O, δ15Nα (central N atom in N2O), and δ15Nβ (terminal N atom) of N2O produced by purified fungal cytochrome P450 nitric oxide reductase (P450nor) from Histoplasma capsulatum as well as bacterial cytochrome c dependent nitric oxide reductase (cNOR) from Paracoccus denitrificans. P450nor exhibits an inverse kinetic isotope effect for Nβ (KIE = 0.9651) but a normal isotope effect for both Nα (KIE = 1.0127) and the oxygen atom (KIE = 1.0264). These results suggest a mechanism where NO binds to the ferric heme in the P450nor active site and becomes Nβ. Analysis of the NO-binding step indicated a greater difference in zero point energy in the transition state than the ground state, resulting in the inverse KIE observed for Nβ. Following protonation and rearrangement, it is speculated that this complex forms a FeIV-NHOH- species as a key intermediate. Our data are consistent with the second NO (which becomes Nα and O in the N2O product) attacking the FeIV-NHOH- species to generate a FeIII-N2O2H2 complex that enzymatically (as opposed to abiotically) breaks down to release N2O. Conversely, our preliminary data

2,2,2-Trifluoroacetophenone as an organocatalyst for the oxidation of tertiary amines and azines to N-oxides.

Science.gov (United States)

Limnios, Dimitris; Kokotos, Christoforos G

2014-01-07

A cheap, mild and environmentally friendly oxidation of tertiary amines and azines to the corresponding N-oxides is reported by using polyfluoroalkyl ketones as efficient organocatalysts. 2,2,2-Trifluoroacetophenone was identified as the optimum catalyst for the oxidation of aliphatic tertiary amines and azines. This oxidation is chemoselective and proceeds in high-to-quantitative yields utilizing 10 mol % of the catalyst and H2 O2 as the oxidant. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanotextured Spikes of α-Fe2O3/NiFe2O4 Composite for Efficient Photoelectrochemical Oxidation of Water.

Science.gov (United States)

Hussain, Shabeeb; Tavakoli, Mohammad Mahdi; Waleed, Aashir; Virk, Umar Siddique; Yang, Shihe; Waseem, Amir; Fan, Zhiyong; Nadeem, Muhammad Arif

2018-03-27

We demonstrate for the first time the application of p-NiFe 2 O 4 /n-Fe 2 O 3 composite thin films as anode materials for light-assisted electrolysis of water. The p-NiFe 2 O 4 /n-Fe 2 O 3 composite thin films were deposited on planar fluorinated tin oxide (FTO)-coated glass as well as on 3D array of nanospike (NSP) substrates. The effect of substrate (planar FTO and 3D-NSP) and percentage change of each component (i.e., NiFe 2 O 4 and Fe 2 O 3 ) of composite was studied on photoelectrochemical (PEC) water oxidation reaction. This work also includes the performance comparison of p-NiFe 2 O 4 /n-Fe 2 O 3 composite (planar and NSP) devices with pure hematite for PEC water oxidation. Overall, the nanostructured p-NiFe 2 O 4 /n-Fe 2 O 3 device with equal molar 1:1 ratio of NiFe 2 O 4 and Fe 2 O 3 was found to be highly efficient for PEC water oxidation as compared with pure hematite, 1:2 and 1:3 molar ratios of composite. The photocurrent density of 1:1 composite thin film on planar substrate was equal to 1.07 mA/cm 2 at 1.23 V RHE , which was 1.7 times higher current density as compared with pure hematite device (0.63 mA/cm 2 at 1.23 V RHE ). The performance of p-NiFe 2 O 4 /n-Fe 2 O 3 composites in PEC water oxidation was further enhanced by their deposition over 3D-NSP substrate. The highest photocurrent density of 2.1 mA/cm 2 at 1.23 V RHE was obtained for the 1:1 molar ratio p-NiFe 2 O 4 /n-Fe 2 O 3 composite on NSP (NF1-NSP), which was 3.3 times more photocurrent density than pure hematite. The measured applied bias photon-to-current efficiency (ABPE) value of NF1-NSP (0.206%) was found to be 1.87 times higher than that of NF1-P (0.11%) and 4.7 times higher than that of pure hematite deposited on FTO-coated glass (0.044%). The higher PEC water oxidation activity of p-NiFe 2 O 4 /n-Fe 2 O 3 composite thin film as compared with pure hematite is attributed to the Z-path scheme and better separation of electrons and holes. The increased surface area and greater light

Nitrous oxide reduction in nodules: denitrification or N2 fixation?

International Nuclear Information System (INIS)

Coyne, M.S.; Focht, D.D.

1987-01-01

Detached cowpea nodules that contained a nitrous oxide reductase-positive (Nor + ) rhizobium strain (8A55) and a nitrous oxide reductase-negative (Nor - ) rhizobium strain (32H1) were incubated with 1% 15 N 2 O (95 atom% 15 N) in the following three atmospheres: aerobic with C 2 H 2 (10%), aerobic without C 2 H 2 , and anaerobic (argon atmosphere) without C 2 H 2 . The greatest production of 15 N 2 occurred anaerobically with 8A55, yet very little was formed with 32H1. Although acetylene reduction activity was slightly higher with 32H1, about 10 times more 15 N 2 was produced aerobically by 8A55 than by 32H1 in the absence of acetylene. The major reductive pathway of N 2 O reduction by denitrifying rhizobium strain 8A55 is by nitrous oxide reductase rather than nitrogenase

K‑Doped Co−Mn−Al Mixed Oxide Catalyst for N2O Abatement from\

Czech Academy of Sciences Publication Activity Database

Pacultová, K.; Karásková, K.; Kovanda, F.; Jirátová, Květa; Šrámek, J.; Kustrovski, P.; Kotarba, A.; Chromčáková, Ž.; Kočí, K.; Obalová, L.

2016-01-01

Roč. 55, č. 26 (2016), s. 7076-7084 ISSN 0888-5885 R&D Projects: GA ČR GA14-13750S; GA TA ČR TA01020336 Institutional support: RVO:67985858 Keywords : Co-Mn-Al mixed oxide * N2O decomposition * HNO3 pilot plant Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.843, year: 2016

Pt/MOx/SiO2, Pt/MOx/TiO2, and Pt/MOx/Al2O3 Catalysts for CO Oxidation

Directory of Open Access Journals (Sweden)

Hongmei Qin

2015-04-01

Full Text Available Conventional supported Pt catalysts have often been prepared by loading Pt onto commercial supports, such as SiO2, TiO2, Al2O3, and carbon. These catalysts usually have simple metal-support (i.e., Pt-SiO2 interfaces. To tune the catalytic performance of supported Pt catalysts, it is desirable to modify the metal-support interfaces by incorporating an oxide additive into the catalyst formula. Here we prepared three series of metal oxide-modified Pt catalysts (i.e., Pt/MOx/SiO2, Pt/MOx/TiO2, and Pt/MOx/Al2O3, where M = Al, Fe, Co, Cu, Zn, Ba, La for CO oxidation. Among them, Pt/CoOx/SiO2, Pt/CoOx/TiO2, and Pt/CoOx/Al2O3 showed the highest catalytic activities. Relevant samples were characterized by N2 adsorption-desorption, X-ray diffraction (XRD, transmission electron microscopy (TEM, H2 temperature-programmed reduction (H2-TPR, X-ray photoelectron spectroscopy (XPS, CO temperature-programmed desorption (CO-TPD, O2 temperature-programmed desorption (O2-TPD, and CO2 temperature-programmed desorption (CO2-TPD.

Mechanistic analysis of temperature-dependent current conduction through thin tunnel oxide in n+-polySi/SiO2/n+-Si structures

Science.gov (United States)

Samanta, Piyas

2017-09-01

We present a detailed investigation on temperature-dependent current conduction through thin tunnel oxides grown on degenerately doped n-type silicon (n+-Si) under positive bias ( VG ) on heavily doped n-type polycrystalline silicon (n+-polySi) gate in metal-oxide-semiconductor devices. The leakage current measured between 298 and 573 K and at oxide fields ranging from 6 to 10 MV/cm is primarily attributed to Poole-Frenkel (PF) emission of trapped electrons from the neutral electron traps located in the silicon dioxide (SiO2) band gap in addition to Fowler-Nordheim (FN) tunneling of electrons from n+-Si acting as the drain node in FLOating gate Tunnel OXide Electrically Erasable Programmable Read-Only Memory devices. Process-induced neutral electron traps are located at 0.18 eV and 0.9 eV below the SiO2 conduction band. Throughout the temperature range studied here, PF emission current IPF dominates FN electron tunneling current IFN at oxide electric fields Eox between 6 and 10 MV/cm. A physics based new analytical formula has been developed for FN tunneling of electrons from the accumulation layer of degenerate semiconductors at a wide range of temperatures incorporating the image force barrier rounding effect. FN tunneling has been formulated in the framework of Wentzel-Kramers-Brilloiun taking into account the correction factor due to abrupt variation of the energy barrier at the cathode/oxide interface. The effect of interfacial and near-interfacial trapped-oxide charges on FN tunneling has also been investigated in detail at positive VG . The mechanism of leakage current conduction through SiO2 films plays a crucial role in simulation of time-dependent dielectric breakdown of the memory devices and to precisely predict the normal operating field or applied floating gate (FG) voltage for lifetime projection of the devices. In addition, we present theoretical results showing the effect of drain doping concentration on the FG leakage current.

The influence of manganese–cobalt oxide/graphene on reducing fire hazards of poly(butylene terephthalate)

Energy Technology Data Exchange (ETDEWEB)

Wang, Dong; Zhang, Qiangjun; Zhou, Keqing; Yang, Wei [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); USTC-CityU Joint Advanced Research Centre, Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, 166 Ren’ai Road, Suzhou, Jiangsu 215123 (China); Gong, Xinglong, E-mail: gongxl@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); CAS Key Laboratory of Mechanical Behaviour and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2014-08-15

Highlights: • MnCo{sub 2}O{sub 4}–GNS hybrids are synthesized by a two-stage liquid phase method. • MnCo{sub 2}O{sub 4}–GNS/PBT composites were prepared via a masterbatch-melt blending method. • Fire hazards are monitored and evaluated by cone calorimeter and TG-IR. • MnCo{sub 2}O{sub 4}–GNS hybrids decrease thermal hazards and smoke hazards of PBT composites. • MnCo{sub 2}O{sub 4}–GNS hybrids perform better catalytic oxidation of CO and organic volatile. - Abstract: By means of direct nucleation and growth on the surface of graphene and element doping of cobalt oxide (Co{sub 3}O{sub 4}) nano-particles, manganese–cobalt oxide/graphene hybrids (MnCo{sub 2}O{sub 4}–GNS) were synthesized to reduce fire hazards of poly(butylene terephthalate) (PBT). The structure, elemental composition and morphology of the obtained hybrids were surveyed by X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy, respectively. Thermogravimetric analysis was applied to simulate and study the influence of MnCo{sub 2}O{sub 4}–GNS hybrids on thermal degradation of PBT during combustion. The fire hazards of PBT and its composites were assessed by the cone calorimeter. The cone test results had showed that peak HRR and SPR values of MnCo{sub 2}O{sub 4}–GNS/PBT composites were lower than that of pure PBT and Co{sub 3}O{sub 4}–GNS/PBT composites. Furthermore, the incorporation of MnCo{sub 2}O{sub 4}–GNS hybrids gave rise to apparent decrease of pyrolysis products containing aromatic compounds, carbonyl compounds, carbon monoxide and carbon dioxide, attributed to combined impact of physical barrier for graphene and cat O{sub 4} for organic volatiles and carbon monoxide.

The influence of manganese–cobalt oxide/graphene on reducing fire hazards of poly(butylene terephthalate)

International Nuclear Information System (INIS)

Wang, Dong; Zhang, Qiangjun; Zhou, Keqing; Yang, Wei; Hu, Yuan; Gong, Xinglong

2014-01-01

Highlights: • MnCo 2 O 4 –GNS hybrids are synthesized by a two-stage liquid phase method. • MnCo 2 O 4 –GNS/PBT composites were prepared via a masterbatch-melt blending method. • Fire hazards are monitored and evaluated by cone calorimeter and TG-IR. • MnCo 2 O 4 –GNS hybrids decrease thermal hazards and smoke hazards of PBT composites. • MnCo 2 O 4 –GNS hybrids perform better catalytic oxidation of CO and organic volatile. - Abstract: By means of direct nucleation and growth on the surface of graphene and element doping of cobalt oxide (Co 3 O 4 ) nano-particles, manganese–cobalt oxide/graphene hybrids (MnCo 2 O 4 –GNS) were synthesized to reduce fire hazards of poly(butylene terephthalate) (PBT). The structure, elemental composition and morphology of the obtained hybrids were surveyed by X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy, respectively. Thermogravimetric analysis was applied to simulate and study the influence of MnCo 2 O 4 –GNS hybrids on thermal degradation of PBT during combustion. The fire hazards of PBT and its composites were assessed by the cone calorimeter. The cone test results had showed that peak HRR and SPR values of MnCo 2 O 4 –GNS/PBT composites were lower than that of pure PBT and Co 3 O 4 –GNS/PBT composites. Furthermore, the incorporation of MnCo 2 O 4 –GNS hybrids gave rise to apparent decrease of pyrolysis products containing aromatic compounds, carbonyl compounds, carbon monoxide and carbon dioxide, attributed to combined impact of physical barrier for graphene and cat O 4 for organic volatiles and carbon monoxide

UV-induced N2O emission from plants

Science.gov (United States)

Bruhn, Dan; Albert, Kristian R.; Mikkelsen, Teis N.; Ambus, Per

2014-12-01

Nitrous oxide (N2O) is an important long-lived greenhouse gas and precursor of stratospheric ozone-depleting mono-nitrogen oxides. The atmospheric concentration of N2O is persistently increasing; however, large uncertainties are associated with the distinct source strengths. Here we investigate for the first time N2O emission from terrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurements to investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and without UV-screening. Further laboratory tests were conducted with a range of species to study the controls and possible loci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c. 20-50 nmol m-2h-1, mostly due to the UV component. The emission response to UV-A is of the same magnitude as that to UV-B. Therefore, UV-A is more important than UV-B given the natural UV-spectrum at Earth's surface. Plants also emitted N2O in darkness, although at reduced rates. The emission rate is temperature dependent with a rather high activation energy indicative for an abiotic process. The prevailing zone for the N2O formation appears to be at the very surface of leaves. However, only c. 26% of the UV-induced N2O appears to originate from plant-N. Further, the process is dependent on atmospheric oxygen concentration. Our work demonstrates that ecosystem emission of the important greenhouse gas, N2O, may be up to c. 30% higher than hitherto assumed.

The Sr2.75Ce0.25Co2O7-δ oxide, n=2 member of the Ruddlesden-Popper series: Structural and magnetic evolution depending on oxygen stoichiometry

International Nuclear Information System (INIS)

Demont, A.; Hebert, S.; Pelloquin, D.; Maignan, A.

2008-01-01

The second member of the Ruddlesden-Popper series, n=2 in Sr n+1 Co n O 3n+1 , has been stabilized by substituting cerium for strontium leading to the pure compound Sr 2.75 Ce 0.25 Co 2 O 7-δ . The oxygen vacancies of this phase can be partially filled by a post-annealing oxidizing treatment with δ decreasing from 1.1 to 0.3 for the as-prepared and oxidized phases, respectively. As the samples are oxidized from δ∼1.1 to 0.3, the a and b unit cell parameters decrease from 3.836 to 3.815 A and from 20.453 to 20.047 A, respectively. Despite the average value of the cobalt valence state, V Co ∼+3.5, obtained in the oxidized Sr 2.75 Ce +4 0.25 Co 2 O 6.7 phase, a clear ferromagnetic state wit T C =175 K and M S =0.8 μB/Co is reached. - Graphical abstract: Temperature dependence of the magnetic susceptibility of as-prepared and PO 2 annealing Sr 2.75 Ce 0.25 Co 2 O 7-δ RP2-type structures

Photocatalytic Decomposition of N2O on Ag-TiO2

Czech Academy of Sciences Publication Activity Database

Kočí, K.; Krejčíková, Simona; Šolcová, Olga; Obalová, L.

2012-01-01

Roč. 191, č. 1 (2012), s. 134-137 ISSN 0920-5861. [International Symposium on Nitrogen Oxides Emission Abatement. Zakopane, 04.09.2011-07.09.2011] R&D Projects: GA ČR GA104/09/0694 Institutional support: RVO:67985858 Keywords : photocatalytic decomposition * N2O * Ag doping * TiO2 Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.980, year: 2012

Properties of slow traps of ALD Al{sub 2}O{sub 3}/GeO{sub x}/Ge nMOSFETs with plasma post oxidation

Energy Technology Data Exchange (ETDEWEB)

Ke, M., E-mail: kiramn@mosfet.t.u-tokyo.ac.jp; Yu, X.; Chang, C.; Takenaka, M.; Takagi, S. [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan and JST-CREST, K' s Gobancho 6F, 7 Gobancho, Chiyoda-ku, Tokyo 102-0076 (Japan)

2016-07-18

The realization of Ge gate stacks with a small amount of slow trap density as well as thin equivalent oxide thickness and low interface state density (D{sub it}) is a crucial issue for Ge CMOS. In this study, we examine the properties of slow traps, particularly the location of slow traps, of Al{sub 2}O{sub 3}/GeO{sub x}/n-Ge and HfO{sub 2}/Al{sub 2}O{sub 3}/GeO{sub x}/n-Ge MOS interfaces with changing the process and structural parameters, formed by atomic layer deposition (ALD) of Al{sub 2}O{sub 3} and HfO{sub 2}/Al{sub 2}O{sub 3} combined with plasma post oxidation. It is found that the slow traps can locate in the GeO{sub x} interfacial layer, not in the ALD Al{sub 2}O{sub 3} layer. Furthermore, we study the time dependence of channel currents in the Ge n-MOSFETs with 5-nm-thick Al{sub 2}O{sub 3}/GeO{sub x}/Ge gate stacks, with changing the thickness of GeO{sub x}, in order to further clarify the position of slow traps. The time dependence of the current drift and the effective time constant of slow traps do not change among the MOSFETs with the different thickness GeO{sub x}, demonstrating that the slow traps mainly exist near the interfaces between Ge and GeO{sub x}.

Epitaxial Sb-doped SnO_2 and Sn-doped In_2O_3 transparent conducting oxide contacts on GaN-based light emitting diodes

International Nuclear Information System (INIS)

Tsai, Min-Ying; Bierwagen, Oliver; Speck, James S.

2016-01-01

We demonstrate the growth of epitaxial (100)-oriented, rutile Sb-doped SnO_2 (ATO) and (111)-oriented, cubic Sn-doped In_2O_3 (ITO) transparent conducting oxide (TCO) contacts on top of an InGaN/GaN(0001) light emitting diode (LED) by plasma-assisted molecular beam epitaxy (PAMBE). Both oxides form rotational domains. The in-plane epitaxial alignment of the two ITO(111) rotational domains to the GaN(0001) was: GaN [21-10]|| ITO_D_o_m_a_i_n_1[‐ 211]|| ITO_D_o_m_a_i_n_2[‐ 1‐12]. A growth temperature as low as 600 °C was necessary to realize a low contact resistance between ATO and the top p-GaN layer of the LED but resulted in non-optimal resistivity (3.4 × 10"− "3 Ω cm) of the ATO. The current–voltage characteristics of a processed LED, however, were comparable to that of a reference LED with a standard electron-beam evaporated ITO top contact. At short wavelengths, the optical absorption of ATO was lower than that of ITO, which is beneficial even for blue LEDs. Higher PAMBE growth temperatures resulted in lower resistive ATO but higher contact resistance to the GaN, likely by the formation of an insulating Ga_2O_3 interface layer. The ITO contact grown by PAMBE at 600 °C showed extremely low resistivity (10"−"4 Ω cm) and high crystalline and morphological quality. These proof-of-principle results may lead to the development of epitaxial TCO contacts with low resistivity, well-defined interfaces to the p-GaN to help minimize contact losses, and enable further epitaxy on top of the TCO. - Highlights: • Plasma-assisted molecular beam epitaxy of SnO_2:Sb (ATO) and In_2O_3:Sn (ITO) contacts • Working light emitting diodes processed with the ATO contact on the top p-GaN layer • Low growth temperature ensures low contact resistance (limiting interface reaction). • ITO showed significantly better structural and transport properties than ATO. • ATO showed higher optical transmission at short wavelengths than ITO.

Photooxidative desulfurization for diesel using Fe / N - TiO2 photocatalyst

Science.gov (United States)

Khan, Muhammad Saqib; Kait, Chong Fai; Mutalib, Mohd Ibrahim Abdul

2014-10-01

A series of N - TiO2 with different mol% N was synthesized via sol-gel method and characterized using thermal gravimetric analyzer and raman spectroscopy. 0.2 wt% Fe was incorporated onto the calcined (200°C) N - TiO2 followed by calcination at 200°C, 250°C and 300°C. Photooxidative desulfurization was conducted in the presence of 0.2wt% Fe / N - TiO2 with different mol% N with and without oxidant (H2O2). Oxidative desulfurization was only achieved when H2O2 was used while without H2O2 no major effect on the sulfur removal. 0.2Fe -30N - H2O2 photocatalysts showed best performance at all calcination temperatures as compared to other mol% N - H2O2 photocatalysts. 16.45% sulfur removal was achieved using photocatalysts calcined at 300 °C.

Plasma-assisted atomic layer deposition of TiN/Al2O3 stacks for metal-oxide-semiconductor capacitor applications

NARCIS (Netherlands)

Hoogeland, D.; Jinesh, K.B.; Roozeboom, F.; Besling, W.F.A.; Sanden, van de M.C.M.; Kessels, W.M.M.

2009-01-01

By employing plasma-assisted atomic layer deposition, thin films of Al2O3 and TiN are subsequently deposited in a single reactor at a single substrate temperature with the objective of fabricating high-quality TiN/Al2O3 / p-Si metal-oxide-semiconductor capacitors. Transmission electron microscopy

Heterojunction solar cell with 6% efficiency based on an n-type aluminum-gallium-oxide thin film and p-type sodium-doped Cu2O sheet

Science.gov (United States)

Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

2015-02-01

In this paper, we describe efforts to enhance the efficiency of Cu2O-based heterojunction solar cells fabricated with an aluminum-gallium-oxide (Al-Ga-O) thin film as the n-type layer and a p-type sodium (Na)-doped Cu2O (Cu2O:Na) sheet prepared by thermally oxidizing copper sheets. The optimal Al content [X; Al/(Ga + Al) atomic ratio] of an AlX-Ga1-X-O thin-film n-type layer was found to be approximately 2.5 at. %. The optimized resistivity was approximately 15 Ω cm for n-type AlX-Ga1-X-O/p-type Cu2O:Na heterojunction solar cells. A MgF2/AZO/Al0.025-Ga0.975-O/Cu2O:Na heterojunction solar cell with 6.1% efficiency was fabricated using a 60-nm-thick n-type oxide thin-film layer and a 0.2-mm-thick Cu2O:Na sheet with the optimized resistivity.

Mitigating climate change through the understanding of Nitrous Oxide (N2O) consumption processes in peat lands

Science.gov (United States)

Akrami, N.; Barker, X. Z.; Horwath, W. R.

2017-12-01

Nitrous Oxide (N2O) with global warming potential of 298 over a 100-year horizon is one of the most potent green house gases. In the United States, agriculture share to N2O emissions is over 70%. Peat lands, however, are being considered as both sources and sinks of greenhouse gases. N2O emissions are a product of both production and consumption processes. However, there is still a lack of understanding of N2O consumption processes in soils. In this work, the potential of re-wetted peat lands planted to rice in Sacramento-San Joaquin Delta, California, to act as a potential sink for N2O is being evaluated. Four peat land soils with 1%, 5%, 11% and 23% of organic carbon have been anaerobically incubated with different water contents (15%, 30%, 50%, 75% and 100% of their water holding capacity). 15N-N2O gas has been injected to the headspace of experiment jars and the production and consumption rate of 15N-N2O, 15N-N2 and production rate of Carbon Dioxide (CO2) and Methane (CH4) along with dissolved Nitrate (NO3-), Nitrite (NO2-), Ammonium (NH4+), Iron (II) and Iron (III) concentration has been quantified. Our results show promising N2O consumption rates under high carbon content and relatively high water content treatments. This research introduces organic carbon and water content as two major criteria in N2O consumption processes in peat lands that make it a potential hotspot for climate changes mitigation through adopting effective management practices to decrease greenhouse gas emissions.

Respiratory transformation of nitrous oxide (N2O) to dinitrogen by Bacteria and Archaea.

Science.gov (United States)

Zumft, Walter G; Kroneck, Peter M H

2007-01-01

N2O is a potent greenhouse gas and stratospheric reactant that has been steadily on the rise since the beginning of industrialization. It is an obligatory inorganic metabolite of denitrifying bacteria, and some production of N2O is also found in nitrifying and methanotrophic bacteria. We focus this review on the respiratory aspect of N2O transformation catalysed by the multicopper enzyme nitrous oxide reductase (N2OR) that provides the bacterial cell with an electron sink for anaerobic growth. Two types of Cu centres discovered in N2OR were both novel structures among the Cu proteins: the mixed-valent dinuclear Cu(A) species at the electron entry site of the enzyme, and the tetranuclear Cu(Z) centre as the first catalytically active Cu-sulfur complex known. Several accessory proteins function as Cu chaperone and ABC transporter systems for the biogenesis of the catalytic centre. We describe here the paradigm of Z-type N2OR, whose characteristics have been studied in most detail in the genera Pseudomonas and Paracoccus. Sequenced bacterial genomes now provide an invaluable additional source of information. New strains harbouring nos genes and capability of N2O utilization are being uncovered. This reveals previously unknown relationships and allows pattern recognition and predictions. The core nos genes, nosZDFYL, share a common phylogeny. Most principal taxonomic lineages follow the same biochemical and genetic pattern and share the Z-type enzyme. A modified N2OR is found in Wolinella succinogenes, and circumstantial evidence also indicates for certain Archaea another type of N2OR. The current picture supports the view of evolution of N2O respiration prior to the separation of the domains Bacteria and Archaea. Lateral nos gene transfer from an epsilon-proteobacterium as donor is suggested for Magnetospirillum magnetotacticum and Dechloromonas aromatica. In a few cases, nos gene clusters are plasmid borne. Inorganic N2O metabolism is associated with a diversity of

Oxidative Dehydrogenation of n-​Butane: Activity and Kinetics Over VOx​/Al2O3 Catalysts

NARCIS (Netherlands)

Madaan, N.; Haufe, R.; Shiju, N.R.; Rothenberg, G.

2014-01-01

The catalytic activity of a VOx/Al2O3 catalyst for the oxidative dehydrogenation of n-​butane is investigated. The effects of reaction temp., oxygen to n-​butane ratio and GHSV on the catalytic performance are examd. and optimized. Interestingly, this simple catalyst gives good conversion and

Mitigation of nitrous oxide (N2O) emissions from denitrifying fluidized bed bioreactors (DFBBRs) using calcium.

Science.gov (United States)

Eldyasti, Ahmed; Nakhla, George; Zhu, Jesse

2014-12-01

Nitrous oxide (N2O) is a significant anthropogenic greenhouse gases (AnGHGs) emitted from biological nutrient removal (BNR) processes. In this study, N2O production from denitrifying fluidized bed bioreactors (DFBBR) was reduced using calcium (Ca2+) dosage. The DFBBRs were operated on a synthetic municipal wastewater at four different calcium concentrations ranging from the typical municipal wastewater Ca2+ concentration (60 mg Ca2+/L) to 240 mg Ca2+/L at two different COD/N ratios. N2O emission rates, extracellular polymeric substances (EPS), water quality parameters, and microscopic images were monitored regularly in both phases. Calcium concentrations played a significant role in biofilm morphology with the detachment rates for R120Ca, R180Ca, and R240Ca 75% lower than for R60Ca, respectively. The N2O conversion rate at the typical municipal wastewater Ca2+ concentration (R60Ca) was about 0.53% of the influent nitrogen loading as compared with 0.34%, 0.42%, and 0.41% for R120Ca, R180Ca, and R240Ca, respectively corresponding to 21-36% reduction. Copyright © 2014 Elsevier Ltd. All rights reserved.

C, N co-doped TiO_2/TiC_0_._7N_0_._3 composite coatings prepared from TiC_0_._7N_0_._3 powder using ball milling followed by oxidation

International Nuclear Information System (INIS)

Hao, Liang; Wang, Zhenwei; Zheng, Yaoqing; Li, Qianqian; Guan, Sujun; Zhao, Qian; Cheng, Lijun; Lu, Yun; Liu, Jizi

2017-01-01

Highlights: • TiO_2/TiC_0_._7N_0_._3 coatings were prepared by ball milling followed by oxidation. • In situ co-doping of C and N with simultaneous TiO_2 formation was observed. • Improved photocatalytic activity under UV/visible light was noticed. • Synergism in co-doping and heterojunction formation promoted carrier separation. - Abstract: Ball milling followed by heat oxidation was used to prepared C, N co-doped TiO_2 coatings on the surfaces of Al_2O_3 balls from TiC_0_._7N_0_._3 powder. The as-prepared coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectrophotometer (UV–vis). The results show that continuous TiC_0_._7N_0_._3 coatings were formed after ball milling. C, N co-doped TiO_2/TiC_0_._7N_0_._3 composite coatings were prepared after the direct oxidization of TiC_0_._7N_0_._3 coatings in the atmosphere. However, TiO_2 was hardly formed in the surface layer of TiC_0_._7N_0_._3 coatings within a depth less than 10 nm during the heat oxidation of TiC_0_._7N_0_._3 coatings in carbon powder. Meanwhile, the photocatalytic activity evaluation of these coatings was conducted under the irradiation of UV and visible light. All the coatings showed photocatalytic activity in the degradation of MB no matter under the irradiation of UV or visible light. The C, N co-doped TiO_2/TiC_0_._7N_0_._3 composite coatings showed the most excellent performance. The enhancement under visible light irradiation should attribute to the co-doping of carbon and nitrogen, which enhances the absorption of visible light. The improvement of photocatalytic activity under UV irradiation should attribute to the synergistic effect of C, N co-doping, the formation of rutile-anatase mixed phases and the TiO_2/TiC_0_._7N_0_._3 composite microstructure.

Degradation mechanism of alachlor during direct ozonation and O(3)/H(2)O(2) advanced oxidation process.

Science.gov (United States)

Qiang, Zhimin; Liu, Chao; Dong, Bingzhi; Zhang, Yalei

2010-01-01

The degradation of alachlor by direct ozonation and advanced oxidation process O(3)/H(2)O(2) was investigated in this study with focus on identification of degradation byproducts. The second-order reaction rate constant between ozone and alachlor was determined to be 2.5+/-0.1M(-1)s(-1) at pH 7.0 and 20 degrees C. Twelve and eight high-molecular-weight byproducts (with the benzene ring intact) from alachlor degradation were identified during direct ozonation and O(3)/H(2)O(2), respectively. The common degradation byproducts included N-(2,6-diethylphenyl)-methyleneamine, 8-ethyl-3,4-dihydro-quinoline, 8-ethyl-quinoline, 1-chloroacetyl-2-hydro-3-ketone-7-acetyl-indole, 2-chloro-2',6'-diacetyl-N-(methoxymethyl)acetanilide, 2-chloro-2'-acetyl-6'-ethyl-N-(methoxymethyl)-acetanilide, and two hydroxylated alachlor isomers. In direct ozonation, four more byproducts were also identified including 1-chloroacetyl-2,3-dihydro-7-ethyl-indole, 2-chloro-2',6'-ethyl-acetanilide, 2-chloro-2',6'-acetyl-acetanilide and 2-chloro-2'-ethyl-6'-acetyl-N-(methoxymethyl)-acetanilide. Degradation of alachlor by O(3) and O(3)/H(2)O(2) also led to the formation of low-molecular-weight byproducts including formic, acetic, propionic, monochloroacetic and oxalic acids as well as chloride ion (only detected in O(3)/H(2)O(2)). Nitrite and nitrate formation was negligible. Alachlor degradation occurred via oxidation of the arylethyl group, N-dealkylation, cyclization and cleavage of benzene ring. After O(3) or O(3)/H(2)O(2) treatment, the toxicity of alachlor solution examined by the Daphnia magna bioassay was slightly reduced. 2009 Elsevier Ltd. All rights reserved.

Estimating N2O processes during grassland renewal and grassland conversion to maize cropping using N2O isotopocules

Science.gov (United States)

Buchen, Caroline; Well, Reinhard; Flessa, Heinz; Fuß, Roland; Helfrich, Mirjam; Lewicka-Szczebak, Dominika

2017-04-01

Grassland break-up due to grassland renewal and grassland conversion to cropland can lead to a flush of mineral nitrogen from decomposition of the old grass sward and the decomposition of soil organic matter. Moreover, increased carbon and nitrogen mineralisation can result in enhanced nitrous oxide (N2O) emissions. As N2O is known to be an important greenhouse gas and a major precursor for ozone depletion, its emissions need to be mitigated by adjusting agricultural management practices. Therefore, it is necessary to understand the N2O processes involved, as well as the contribution of N2O reduction to N2. Apart from the widely used 15N gas flux method, natural abundance isotopic analysis of the four most abundant isotopocules of N2O species is a promising alternative to assess N2O production pathways. We used stable isotope analyses of soil-emitted N2O (δ18ON2O, δ15NN2Obulk and δ15NN2OSP= intramolecular distribution of 15N within the linear N2O molecule) with an isotopocule mapping approach to simultaneously estimate the magnitude of N2O reduction to N2 and the fraction of N2O originating from the bacterial denitrification pathway or fungal denitrification and/or nitrification. This approach is based on endmember areas of isotopic values for the N2O produced from different sources reported in the literature. For this purpose, we calculated two main scenarios with different assumptions for N2O produced: N2O is reduced to N2 before residual N2O is mixed with N2O of various sources (Scenario a) and vice versa (Scenario b). Based on this, we applied seven different scenario variations, where we evaluated the range of possible values for the potential N2O production pathways (heterotrophic bacterial denitrification and/or nitrifier denitrification and fungal denitrification and/or nitrification). This was done by using a range of isotopic endmember values and assuming different fractionation factors of N2O reduction in order to find the most reliable scenario

Properties of TiO2-based transparent conducting oxide thin films on GaN(0001) surfaces

International Nuclear Information System (INIS)

Kasai, J.; Nakao, S.; Yamada, N.; Hitosugi, T.; Moriyama, M.; Goshonoo, K.; Hoang, N. L. H.; Hasegawa, T.

2010-01-01

Anatase Nb-doped TiO 2 transparent conducting oxide has been formed on GaN(0001) surfaces using a sputtering method. Amorphous films deposited at room temperature were annealed at a substrate temperature of 500 deg. C in vacuum to form single-phase anatase films. Films with a thickness of 170 nm exhibited a resistivity of 8x10 -4 Ω cm with absorptance less than 5% at a wavelength of 460 nm. Furthermore, the refractive index of the Nb-doped TiO 2 was well matched to that of GaN. These findings indicate that Nb-doped TiO 2 is a promising material for use as transparent electrodes in GaN-based light emitting diodes (LEDs), particularly since reflection at the electrode/GaN boundary can be suppressed, enhancing the external quantum efficiency of blue LEDs.

Growth of Ga{sub 2}O{sub 3} by furnace oxidation of GaN studied by perturbed angular correlations

Energy Technology Data Exchange (ETDEWEB)

Steffens, Michael, E-mail: michael.steffens@int.fraunhofer.de [Fraunhofer Institute for Technological Trend Analysis INT (Germany); Vianden, Reiner [Helmholtz - Institut für Strahlen- und Kernphysik der Universität Bonn (Germany); Pasquevich, Alberto F. [Universidad Nacional de La Plata, Departamento de Física, IFLP, Facultad de Ciencias Exactas (Argentina)

2016-12-15

Ga{sub 2}O{sub 3} is a promising material for use in “solar-blind” UV-detectors which can be produced efficiently by oxidation of GaN. In this study we focus on the evolution of the oxide layer when GaN is heated in air. The experimental method applied is the perturbed angular correlation (PAC) spectroscopy of γ-rays emitted by radioactive nuclides, here {sup 111}Cd and {sup 181}Ta, whose parent nuclei are ion implanted into films of GaN grown on sapphire. As the emission pattern for nuclei in GaN is clearly distinct from that of nuclei in Ga{sub 2}O{sub 3}, the fraction of probe nuclei in the oxide layer can be directly measured and allows to follow the time dependent growth of the oxide on a scale of less than 100 nm. Additional measurements were carried out with the oxidized sample held at fixed temperatures in the temperature range from 19 K to 973 K showing transitions between the hyperfine interactions of {sup 111}Cd in the oxide matrix both at high and low temperatures. A model for these transitions is proposed.

Modeling on oxide dependent 2DEG sheet charge density and threshold voltage in AlGaN/GaN MOSHEMT

Science.gov (United States)

Panda, J.; Jena, K.; Swain, R.; Lenka, T. R.

2016-04-01

We have developed a physics based analytical model for the calculation of threshold voltage, two dimensional electron gas (2DEG) density and surface potential for AlGaN/GaN metal oxide semiconductor high electron mobility transistors (MOSHEMT). The developed model includes important parameters like polarization charge density at oxide/AlGaN and AlGaN/GaN interfaces, interfacial defect oxide charges and donor charges at the surface of the AlGaN barrier. The effects of two different gate oxides (Al2O3 and HfO2) are compared for the performance evaluation of the proposed MOSHEMT. The MOSHEMTs with Al2O3 dielectric have an advantage of significant increase in 2DEG up to 1.2 × 1013 cm-2 with an increase in oxide thickness up to 10 nm as compared to HfO2 dielectric MOSHEMT. The surface potential for HfO2 based device decreases from 2 to -1.6 eV within 10 nm of oxide thickness whereas for the Al2O3 based device a sharp transition of surface potential occurs from 2.8 to -8.3 eV. The variation in oxide thickness and gate metal work function of the proposed MOSHEMT shifts the threshold voltage from negative to positive realizing the enhanced mode operation. Further to validate the model, the device is simulated in Silvaco Technology Computer Aided Design (TCAD) showing good agreement with the proposed model results. The accuracy of the developed calculations of the proposed model can be used to develop a complete physics based 2DEG sheet charge density and threshold voltage model for GaN MOSHEMT devices for performance analysis.

Effects of the silica nanoparticles (NPSiO2 on the stabilization and transport of hazardous nanoparticle suspensions into landfill soil columns

Directory of Open Access Journals (Sweden)

Elizabeth Mendes de Oliveira

Full Text Available Abstract This study evaluates the stability and transport behaviors of hazardous nanoparticles into soil landfills using experimental procedures to simulate the effects of natural silica nanoparticle suspensions during their percolation into the soil layers of municipal waste landfills. For this, we prepared stabilized suspensions of nanoparticle oxides containing silicon (NPSiO2, titanium (NPTiO2, copper (NPCuO and zinc (NPZnO, which are recognized as hazardous to the environment, and we conducted leaching experiments within the soil column by simulating landfills layers and simulating the capture and attenuation of nanomaterials into municipal waste landfills. The results demonstrated that the presence of NPSiO2 in suspensions increases the stable concentrations of copper, zinc and titanium oxides and strongly decreases soil layer effectiveness. In contrast, NPZnO improves effectiveness due to its ability to promote agglomeration and setting conditions, allowing further complexation.

catena-Poly[lead(II-[μ-2,4-diamino-6-(piperidin-1-ylpyrimidine N-oxide-κ2O:O]di-μ-iodido

Directory of Open Access Journals (Sweden)

Maryam Ranjbar

2009-07-01

Full Text Available The N-oxide O atom of the minoxidil unit in the 1/1 adduct with lead(II iodide, [PbI2(C9H15N5O]n, bridges two PbII atoms, as do each of the I atoms. The bridging interactions give rise to a linear chain motif that propagates along the a axis of the orthorhombic unit cell. The coordination sphere around the six-coordinate PbII atom is a distorted ψ-monocapped octahedron in which the stereochemically active lone pair caps one of the faces defined by the O and I atoms forming the longer Pb—O or Pb—I bonds. The PbII atom lies on a mirror plane; the mirror plane is perpendicular to the pyrimidine ring and it bisects the piperidine ring. The aromatic ring is disordered about the mirror plane with respect to the 1-nitrogen and 5-carbon atoms.

Reduced graphene oxide wrapped Cu2O supported on C3N4: An efficient visible light responsive semiconductor photocatalyst

Science.gov (United States)

Ganesh Babu, S.; Vinoth, R.; Surya Narayana, P.; Bahnemann, Detlef; Neppolian, B.

2015-10-01

Herein, Cu2O spheres were prepared and encapsulated with reduced graphene oxide (rGO). The Cu2O-rGO-C3N4 composite covered the whole solar spectrum with significant absorption intensity. rGO wrapped Cu2O loading caused a red shift in the absorption with respect to considering the absorption of bare C3N4. The photoluminescence study confirms that rGO exploited as an electron transport layer at the interface of Cu2O and C3N4 heterojunction. Utmost, ˜2 fold synergistic effect was achieved with Cu2O-rGO-C3N4 for the photocatalytic reduction of 4-nitrophenol to 4-aminophenol in comparison with Cu2O-rGO and C3N4. The Cu2O-rGO-C3N4 photocatalyst was reused for four times without loss in its activity.

Pathways and Controls of N₂O Production in Nitritation-Anammox Biomass

DEFF Research Database (Denmark)

Ma, Chun; Jensen, Marlene Mark; Smets, Barth F.

2017-01-01

to investigate pathways and controls of N2O production by biomass taken from a full-scale nitritation-anammox reactor. The experiments showed that heterotrophic denitrification was a negligible source of N2O under oxic conditions (≥0.2 mg O2 L-1). Both hydroxylamine oxidation and nitrifier denitrification...... of N2O production from hydroxylamine oxidation at low O2 was unexpected and suggests that more than one enzymatic pathway may be involved in this process. N2O production by hydroxylamine oxidation was further stimulated by NH4+, whereas nitrifier denitrification at low O2 levels was stimulated by NO2...

Electroless deposition and electrical characterization of N- Cu 2 O ...

African Journals Online (AJOL)

This work describes the preparation of n-Cu2O layer by the electroless methods of boiling and immersion of copper plates in 0.001M CuSO4Electron Microscopy (SEM) have been used to characterize the oxide films deposited. XRD studies show, for the first time, that cuprous oxide (Cu2O) and cupric oxide (CuO) were ...

Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

Science.gov (United States)

Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

2017-02-01

TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.

Assessment of cellular responses to oxidative stress using MCF-7 breast cancer cells, black seed (N. Sativa L.) extracts and H2O2.

Science.gov (United States)

Farah, Ibrahim O

2005-12-01

Black seed (N. Sativa L) is an oriental spice of the family Ranunculaceae that has long been rationally used as a natural medicine for treatment of many acute as well as chronic conditions including cardiovascular disease and immunological disorders. It has been used in the treatment of diabetes, hypertension, and dermatological conditions. There have been very few studies on the effects of N. Sativa as a chemoprevention of chronic diseases as well as in cancer prevention and/or therapy. Oxidative stress is a condition that underlies many acute as well as chronic conditions. The combination and role of oxidative stress and antioxidants in vivo is still a matter of conjecture. Our objective for the present study was to expose MCF-7 breast cancer cells in vitro (as a chronic disease example) to aqueous and alcohol extracts and in combination with H[2]O[2] as an oxidative stressor. Measurement of cell survival under various concentrations and mixtures was conducted using standard cell culture techniques, exposure protocols in 96 well plates and Fluorospectrosphotometry. Following cellular growth to 90% confluencey, exposure to water (WE) and ethanol (AE) extracts of N. sativa and H[2]O[2] was performed. Cell survival indices were calculated from percent survival using regression analysis. Results showed that the alcohol extract and its mixtures were able to influence the survival of MCF-7 cells (indices ranged from 357.15- 809.50 mug/ml in descending potency for H[2]O[2]+AE to the mix of 3). In contrast, H[2]O[2] alone reduced effectively the survival of MCF-7 cells and the least effective combinations in descending potency were AE+H[2]O[2], WE+H[2]O[2], AE+WE, and WE+AE+H[2]O[2]. Mixtures other than AE+H[2]O[2] showed possible interactions and loss of potency. In conclusion, N. Sativa alone or in combination with oxidative stress was found to be effective (in vitro) in influencing the survival of MCF-7 breast cancer cells, unveiling promising opportunities in the

Assessment of Cellular Responses to Oxidative Stress using MCF-7 Breast Cancer Cells, Black Seed (N. Sativa L. Extracts and H2O2

Directory of Open Access Journals (Sweden)

Ibrahim O. Farah

2005-12-01

Full Text Available Black seed (N. Sativa L is an oriental spice of the family Ranunculaceae that has long been rationally used as a natural medicine for treatment of many acute as well as chronic conditions including cardiovascular disease and immunological disorders. It has been used in the treatment of diabetes, hypertension, and dermatological conditions. There have been very few studies on the effects of N. Sativa as a chemoprevention of chronic diseases as well as in cancer prevention and/or therapy. Oxidative stress is a condition that underlies many acute as well as chronic conditions. The combination and role of oxidative stress and antioxidants in vivo is still a matter of conjecture. Our objective for the present study was to expose MCF-7 breast cancer cells in vitro (as a chronic disease example to aqueous and alcohol extracts and in combination with H2O2 as an oxidative stressor. Measurement of cell survival under various concentrations and mixtures was conducted using standard cell culture techniques, exposure protocols in 96 well plates and Fluorospectrosphotometry. Following cellular growth to 90% confluencey, exposure to water (WE and ethanol (AE extracts of N. sativa and H2O2 was performed. Cell survival indices were calculated from percent survival using regression analysis. Results showed that the alcohol extract and its mixtures were able to influence the survival of MCF-7 cells (indices ranged from 357.15- 809.50 Bg/ml in descending potency for H2O2+AE to the mix of 3. In contrast, H2O2 alone reduced effectively the survival of MCF-7 cells and the least effective combinations in descending potency were AE+H2O2, WE+H2O2, AE+WE, and WE+AE+H2O2. Mixtures other than AE+H2O2 showed possible interactions and loss of potency. In conclusion, N. Sativa alone or in combination with oxidative stress was found to be effective (in vitro in influencing the survival of MCF-7 breast cancer cells, unveiling promising opportunities in the field of cancer

Topotactic dehydration of the lamellar oxide HK2Ti5NbO14 x H2O: the oxide K4Ti10Nb2O27

International Nuclear Information System (INIS)

Grandin, A.; Borel, M.M.; Hervieu, M.; Raveau, B.

1987-01-01

The lamellar oxide HK 2 Ti 5 NbO 14 x H 2 O can be topotactically dehydrated to K 4 Ti 10 Nb 2 O 27 . Electron diffraction and X-ray diffraction studies of this phase lead to a monoclinic cell with the parameters a = 17.005, b = 3.78, c = 9.01 A and β 92.14 0 . Diffusion streaks on the electron diffraction patterns indicate disorder whereas the existence of two sets of lattices on the same crystal give evidence of the topotactic character of the reaction. A structural model is proposed for K 4 Ti 10 Nb 2 O 27 , which corresponds to the intergrowth of K 3 TiNbO 14 layers with the K 2 Ti 6 O 13 tunnel structure. The possibility of formation of various intergrowths such as (KTi 5 NbO 13 )/sub n/ (HK 2 Ti 5 NbO 14 )/sub n/' is suggested

Physical and electrical characteristics of AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors with rare earth Er2O3 as a gate dielectric

International Nuclear Information System (INIS)

Lin, Ray-Ming; Chu, Fu-Chuan; Das, Atanu; Liao, Sheng-Yu; Chou, Shu-Tsun; Chang, Liann-Be

2013-01-01

In this study, the rare earth erbium oxide (Er 2 O 3 ) was deposited using an electron beam onto an AlGaN/GaN heterostructure to fabricate metal-oxide-semiconductor high-electron-mobility transistors (MOS–HEMTs) that exhibited device performance superior to that of a conventional HEMT. Under similar bias conditions, the gate leakage currents of these MOS–HEMT devices were four orders of magnitude lower than those of conventional Schottky gate HEMTs. The measured sub-threshold swing (SS) and the effective trap state density (N t ) of the MOS–HEMT were 125 mV/decade and 4.3 × 10 12 cm −2 , respectively. The dielectric constant of the Er 2 O 3 layer in this study was 14, as determined through capacitance–voltage measurements. In addition, the gate–source reverse breakdown voltage increased from –166 V for the conventional HEMT to –196 V for the Er 2 O 3 MOS–HEMT. - Highlights: ► GaN/AlGaN/Er 2 O 3 metal-oxide semiconductor high electron mobility transistor ► Physical and electrical characteristics are presented. ► Electron beam evaporated Er 2 O 3 with excellent surface roughness ► Device exhibits reduced gate leakage current and improved I ON /I OFF ratio

Effects of CO, O2, NO, H2O, and irradiation temperature on the radiation-induced oxidation of SO2

International Nuclear Information System (INIS)

Tokunaga, Okihiro; Nishimura, Koichi; Suzuki, Nobutake; Washino, Masamitsu

1977-01-01

When a SO 2 -H 2 O-O 2 -N 2 gaseous mixture was irradiated by electron beams of 1.5 MeV, SO 2 was easily oxidized to H 2 SO 4 . Effects of CO, O 2 , NO, H 2 O, and irradiation temperature on the radiation-induced oxidation of SO 2 were studied by measuring the SO 2 concentration gas chromatographically. The G(-SO 2 ) increased greatly at the addition of a small amount of O 2 , and then decreased gradually with an increase in the O 2 concentration, i.e., the G(-SO 2 ) values were 0.9, 8.0, and 5.3 for the 0, 0.1, and 20% O 2 concentrations at 100 0 C, respectively (Fig.4). The G(-SO 2 ) was independent of the H 2 O concentration in the range of 0.84 to 8.4% (Fig.5). The G(-SO 2 ) decreased with a rise in the irradiation temperature (Fig.6) and an apparent activation energy of the oxidation reaction of SO 2 obtained was -4.2 kcal.mol -1 . The effects of CO, NO, and O 2 on the G(-SO 2 ) showed that SO 2 was mainly oxidized by OH and O and that the contribution of OH to the oxidation of SO 2 increased with an increase in the O 2 concentration (Table 1). The rate constants for the reactions of SO 2 with OH and O, obtained from competitive reactions of SO 2 with CO and O 2 , were 5.4 x 10 11 cm 3 .mol -1 .sec -1 and 5.0 x 10 11 cm 3 .mol -1 .sec -1 , respectively. (auth.)

Photochemical oxidation of short-chain polychlorinated n-alkane mixtures using H2O2/UV and the photo-Fenton reaction

OpenAIRE

Ken J. Friesen; Taha M. El-Morsi; Alaa S. Abd-El-Aziz

2004-01-01

The photochemical oxidation of a series of short-chain polychlorinated n-alkane (PCA) mixtures was investigated using H2O2/UV and modified photo-Fenton conditions (Fe3+/H2O2/UV) in both Milli-Q and lake water. All PCA mixtures, including chlorinated (Cl5 to Cl8) decanes, undecanes, dodecanes and tridecanes degraded in 0.02 M H2O2/UV at pH 2.8 in pure water, with 80±4% disappearance after 3 h of irradiation using a 300 nm light source. Degradation was somewhat enhanced under similar conditions...

Technical Note: Simultaneous measurement of sedimentary N2 and N2O production and a modified 15N isotope pairing technique

Science.gov (United States)

Hsu, T.-C.; Kao, S.-J.

2013-12-01

Dinitrogen (N2) and/or nitrous oxide (N2O) are produced through denitrification, anaerobic ammonium oxidation (anammox) or nitrification in sediments, of which entangled processes complicate the absolute rate estimations of gaseous nitrogen production from individual pathways. The classical isotope pairing technique (IPT), the most common 15N nitrate enrichment method to quantify denitrification, has recently been modified by different researchers to (1) discriminate between the N2 produced by denitrification and anammox or to (2) provide a more accurate denitrification rate under considering production of both N2O and N2. In case 1, the revised IPT focused on N2 production being suitable for the environments of a low N2O-to-N2 production ratio, while in case 2, anammox was neglected. This paper develops a modified method to refine previous versions of IPT. Cryogenic traps were installed to separately preconcentrate N2 and N2O, thus allowing for subsequent measurement of the two gases generated in one sample vial. The precision is better than 2% for N2 (m/z 28, m/z 29 and m/z 30), and 1.5% for N2O (m/z 44, m/z 45 and m/z 46). Based on the six m/z peaks of the two gases, the 15N nitrate traceable processes including N2 and N2O from denitrification and N2 from anammox were estimated. Meanwhile, N2O produced by nitrification was estimated via the production rate of unlabeled 44N2O. To validate the applicability of our modified method, incubation experiments were conducted using sediment cores taken from the Danshuei Estuary in Taiwan. Rates of the aforementioned nitrogen removal processes were successfully determined. Moreover, N2O yield was as high as 66%, which would significantly bias previous IPT approaches if N2O was not considered. Our modified method not only complements previous versions of IPT but also provides more comprehensive information to advance our understanding of nitrogen dynamics of the water-sediment interface.

The Role of Fe2O3 Species in Depressing the Formation of N2O in the Selective Reduction of NO by NH3 over V2O5/TiO2-Based Catalysts

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Moon Hyeon Kim

2018-03-01

Full Text Available Promotion of 2.73% Fe2O3 in an in-house-made V2O5-WO3/TiO2 (VWT and a commercial V2O5-WO3/TiO2 (c-VWT has been investigated as a cost effective approach to the suppression of N2O formation in the selective catalytic reduction of NO by NH3 (NH3-SCR. The promoted VWT and c-VWT catalysts all gave a significantly decreased N2O production at temperatures >400 °C compared to the unpromoted samples. However, such a promotion led to the loss in high temperature NO conversion, mainly due to the oxidation of NH3 to N-containing gases, particularly NO. Characterization of the unpromoted and promoted catalysts using X-ray diffraction (XRD, NH3 adsorption-desorption, and Raman spectroscopy techniques could explain the reason why the promotion showed much lower N2O formation levels at high temperatures. The addition of Fe2O3 to c-VWT resulted in redispersion of the V2O5 species, although this was not visible for 2.73% Fe2O3/VWT. The iron oxides exist as a highly-dispersed noncrystalline α-Fe2O3 in the promoted catalysts. These Raman spectra had a new Raman signal that could be tentatively assigned to Fe2O3-induced tetrahedrally coordinated polymeric vanadates and/or surface V-O-Fe species with significant electronic interactions between the both metal oxides. Calculations of the monolayer coverage of each metal oxide and the surface total coverage are reasonably consistent with Raman measurements. The proposed vanadia-based surface polymeric entities may play a key role for the substantial reduction of N2O formed at high temperatures by NH3 species adsorbed strongly on the promoted catalysts. This reaction is a main pathway to greatly suppress the extent of N2O formation in NH3-SCR reaction over the promoted catalysts.

From Ba3Ta5O14N to LaBa2Ta5O13N2: Decreasing the optical band gap of a photocatalyst

International Nuclear Information System (INIS)

Anke, B.; Bredow, T.; Pilarski, M.; Wark, M.; Lerch, M.

2017-01-01

Yellow LaBa 2 Ta 5 O 13 N 2 was successfully synthesized as phase-pure material crystallizing isostructurally to previously reported Ba 3 Ta 5 O 14 N and mixed-valence Ba 3 Ta V 4 Ta IV O 15 . The electronic structure of LaBa 2 Ta 5 O 13 N 2 was studied theoretically with the range-separated hybrid method HSE06. The most stable structure was obtained when lanthanum was placed on 2a and nitrogen on 4h sites confirming Pauling's second rule. By incorporating nitrogen, the measured band gap decreases from ∼3.8 eV for the oxide via 2.74 eV for Ba 3 Ta 5 O 14 N to 2.63 eV for the new oxide nitride, giving rise to an absorption band well in the visible-light region. Calculated fundamental band gaps confirm the experimental trend. The atom-projected density of states has large contributions from N2p orbitals close to the valence band edge. These are responsible for the observed band gap reduction. Photocatalytic hydrogen formation was investigated and compared with that of Ba 3 Ta 5 O 14 N revealing significantly higher activity for LaBa 2 Ta 5 O 13 N 2 under UV-light. - Graphical abstract: X-ray powder diffraction pattern of LaBa 2 Ta 5 O 13 N 2 with the results of the Rietveld refinements. Inset: Unit cell of LaBa 2 Ta 5 O 13 N 2 and polyhedral representation of the crystal structure. - Highlights: • Synthesis of a new oxide nitride LaBa 2 Ta 5 O 13 N 2 . • Refinement of the crystal structure. • Quantum chemical calculations provided band gap close to the measured value. • New phase shows a higher photocatalytic H 2 evolution rate compared to prior tested Ba 3 Ta 5 O 14 N.

Comparison of sol-gel prepared catalysts for CO oxidation and N2O decomposition reactions.

OpenAIRE

Euesden, Claire

2002-01-01

This thesis comprises analysis for two types of catalysis: CO oxidation and N2O decomposition; related by their research in sol-gel catalysis. The CO oxidation work was undertaken on behalf of Servomex plc in order to understand how their catalyst-based sensor (Tfx 1750) worked and why it failed when exposed to coal power station flue streams within its two-year guarantee period. This research will show, by means of many analytical techniques and catalytic tests: 1. A comparison of the Servom...

Environmental risk assessment of engineered nano-SiO2 , nano iron oxides, nano-CeO2 , nano-Al2 O3 , and quantum dots.

Science.gov (United States)

Wang, Yan; Nowack, Bernd

2018-05-01

Many research studies have endeavored to investigate the ecotoxicological hazards of engineered nanomaterials (ENMs). However, little is known regarding the actual environmental risks of ENMs, combining both hazard and exposure data. The aim of the present study was to quantify the environmental risks for nano-Al 2 O 3 , nano-SiO 2 , nano iron oxides, nano-CeO 2 , and quantum dots by comparing the predicted environmental concentrations (PECs) with the predicted-no-effect concentrations (PNECs). The PEC values of these 5 ENMs in freshwaters in 2020 for northern Europe and southeastern Europe were taken from a published dynamic probabilistic material flow analysis model. The PNEC values were calculated using probabilistic species sensitivity distribution (SSD). The order of the PNEC values was quantum dots nano-CeO 2  nano iron oxides nano-Al 2 O 3  nano-SiO 2 . The risks posed by these 5 ENMs were demonstrated to be in the reverse order: nano-Al 2 O 3  > nano-SiO 2  > nano iron oxides > nano-CeO 2  > quantum dots. However, all risk characterization values are 4 to 8 orders of magnitude lower than 1, and no risk was therefore predicted for any of the investigated ENMs at the estimated release level in 2020. Compared to static models, the dynamic material flow model allowed us to use PEC values based on a more complex parameterization, considering a dynamic input over time and time-dependent release of ENMs. The probabilistic SSD approach makes it possible to include all available data to estimate hazards of ENMs by considering the whole range of variability between studies and material types. The risk-assessment approach is therefore able to handle the uncertainty and variability associated with the collected data. The results of the present study provide a scientific foundation for risk-based regulatory decisions of the investigated ENMs. Environ Toxicol Chem 2018;37:1387-1395. © 2018 SETAC. © 2018 SETAC.

Investigation of 'surface donors' in Al2O3/AlGaN/GaN metal-oxide-semiconductor heterostructures: Correlation of electrical, structural, and chemical properties

Science.gov (United States)

Ťapajna, M.; Stoklas, R.; Gregušová, D.; Gucmann, F.; Hušeková, K.; Haščík, Š.; Fröhlich, K.; Tóth, L.; Pécz, B.; Brunner, F.; Kuzmík, J.

2017-12-01

III-N surface polarization compensating charge referred here to as 'surface donors' (SD) was analyzed in Al2O3/AlGaN/GaN metal-oxide-semiconductor (MOS) heterojunctions using scaled oxide films grown by metal-organic chemical vapor deposition at 600 °C. We systematically investigated impact of HCl pre-treatment prior to oxide deposition and post-deposition annealing (PDA) at 700 °C. SD density was reduced down to 1.9 × 1013 cm-2 by skipping HCl pre-treatment step as compared to 3.3 × 1013 cm-2 for structures with HCl pre-treatment followed by PDA. The nature and origin of SD was then analyzed based on the correlation between electrical, micro-structural, and chemical properties of the Al2O3/GaN interfaces with different SD density (NSD). From the comparison between distributions of interface traps of MOS heterojunction with different NSD, it is demonstrated that SD cannot be attributed to interface trapped charge. Instead, variation in the integrity of the GaOx interlayer confirmed by X-ray photoelectron spectroscopy is well correlated with NSD, indicating SD may be formed by border traps at the Al2O3/GaOx interface.

Growth and characterization of tin oxide thin films and fabrication of transparent p-SnO/n-ZnO p–n hetero junction

Energy Technology Data Exchange (ETDEWEB)

Sanal, K.C., E-mail: sanalcusat@gmail.com [Nanophotonic and Optoelectronic Devices Laboratory, Department of Physics, Cochin University of Science and Technology, Kerala 682 022 (India); Inter University Center for Nanomaterials and Devices (IUCND), Cochin University of Science and Technology (India); Jayaraj, M.K. [Nanophotonic and Optoelectronic Devices Laboratory, Department of Physics, Cochin University of Science and Technology, Kerala 682 022 (India)

2013-07-01

Highlights: • Growth of p-type semiconducting SnO thin films by rf sputtering. • Varying the type of charge carriers with oxygen partial pressure. • Atomic percentage of SnO{sub x} thin films from the XPS analysis. • Demonstration of transparent p–n hetero junctions fabricated in the structure glass/ITO/n-ZnO/p-SnO. -- Abstract: p-Type and n-type tin oxide thin films were deposited by rf-magnetron sputtering of metal tin target by varying the oxygen pressure. Chemical composition of SnO thin film according to the intensity of the XPS peak is about 48.85% and 51.15% for tin and oxygen respectively. Nearest neighbor distance of the atoms calculated from SAED patterns is 2.9 Åand 2.7 Åfor SnO and SnO{sub 2} respectively. The Raman scattering spectrum obtained from SnO thin films showed two peaks, one at 113 cm{sup −1} and the other at 211 cm{sup −1}. Band gap of as-deposited SnO{sub x} thin films vary from 1.6 eV to 3.2 eV on varying the oxygen partial pressure from 3% to 30% which indicates the oxidization of metallic phase Sn to SnO and SnO{sub 2}. p-Type conductivity of SnO thin films and n-type conductivity of SnO{sub 2} thin films were confirmed through Hall coefficient measurement. Transparent p–n hetero junction fabricated in the structure glass/ITO/n-ZnO/p-SnO shows rectification with forward to reverse current ratio as 12 at 4.5 V.

On the mechanisms of titanium particle reactions in O{sub 2}/N{sub 2} and O{sub 2}/Ar atmospheres

Energy Technology Data Exchange (ETDEWEB)

Andrzejak, Timothy A.; Shafirovich, Evgeny; Varma, Arvind [School of Chemical Engineering, Purdue University, West Lafayette, IN (United States)

2009-02-15

Combustion of titanium particles in air may potentially be used for the in situ synthesis of nanoscale TiO{sub 2} particles, which can photocatalytically degrade chemical and biological air pollutants. The knowledge of Ti particle reactions in O{sub 2}-containing atmospheres is required to develop this method. In the present work, large ({proportional_to}3 mm) single Ti particles were heated by a laser in O{sub 2}/N{sub 2} and O{sub 2}/Ar environments. High-speed digital video recording, thermocouple measurements and quenching at different stages of the process were used for diagnostics. Analysis of the obtained temperature-time curves and quenched particles does not show a significant influence of nitrogen on the oxidation of solid Ti. In all experiments, noticeable surface oxidation started at temperatures between {proportional_to}850 and {proportional_to}950 C, leading to a sharp temperature rise at {proportional_to}1400 C. During prolonged heating at the Ti melting point (1670 C), a liquid TiO{sub 2} bead formed and, after an induction period, ejected fragments. It was shown that this phenomenon may result from an excess of oxygen in the liquid bead. Fragment ejection in O{sub 2}/N{sub 2} atmospheres was more intense than in O{sub 2}/Ar, indicating that N{sub 2} accelerates the oxidation of liquid Ti. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

Al- or Si-decorated graphene oxide: A favorable metal-free catalyst for the N2O reduction

Science.gov (United States)

Esrafili, Mehdi D.; Sharifi, Fahimeh; Nematollahi, Parisa

2016-11-01

The structural and catalytic properties of Al- or Si-decorated graphene oxide (Al-/Si-GO) are studied by means of density functional theory calculations. The relatively large adsorption energy together with the small Alsbnd O or Sisbnd O binding distances indicate that the epoxy groups over the GO surface can strongly stabilize the single Al or Si atom. Hence, Al-GO and Si-GO are stable enough to be utilized in catalytic reduction of N2O by CO molecule. It is found that the adsorption and decomposition of N2O molecule over Si-GO is more favorable than over Al-GO, due to its larger adsorption energy (Eads) and charge transfer (qCT) values. On the other hand, the CO molecule is physically adsorbed over both surfaces, with relatively small Eads and qCT values. Therefore, at the presence of N2O and CO molecules as the reaction gas, the Al or Si atom of the surface should be dominantly covered by N2O molecule. Our results indicate that the N2O decomposition process can take place with a negligible activation energy over Al-/Si-GO surface, where the N2 molecule can be easily released from the surface. Then, the activated oxygen atom (Oads) which remains over the surface reacts with the CO molecule to form the CO2 molecule via the reaction Oads + CO → CO2. Based on the calculated activation energies, it is suggested that both Al-GO and Si-GO can be used as an efficient metal-free catalyst for the reduction of N2O molecule at ambient conditions.

Enrichment of 15N and 18O by chemical exchange reactions between nitrogen oxides (NO, NO2) and aqueous nitric acid

International Nuclear Information System (INIS)

Abrudean, M.; Axente, D.; Baldea, A.

1981-01-01

The enrichment of 15 N and 18 O by chemical exchange in the NO, NO 2 -H 2 O, HNO 3 system is described. A laboratory experimental plant and a cascade for producing the two isotopes has been used. The production plant consists of two exchange columns for 15 N separation and two 18 O separation columns feeded with nitrogen oxides, depleted of 15 N, from the top of the first 15 N separation column. The by-products nitric acid and sulphuric acid, both depleted of 15 N and 18 O, are of commercial interest. (author)

Factors controlling regional differences in forest soil emission of nitrogen oxides (NO and N2O

Directory of Open Access Journals (Sweden)

K. Pilegaard

2006-01-01

Full Text Available Soil emissions of NO and N2O were measured continuously at high frequency for more than one year at 15 European forest sites as part of the EU-funded project NOFRETETE. The locations represent different forest types (coniferous/deciduous and different nitrogen loads. Geographically they range from Finland in the north to Italy in the south and from Hungary in the east to Scotland in the west. The highest NO emissions were observed from coniferous forests, whereas the lowest NO emissions were observed from deciduous forests. The NO emissions from coniferous forests were highly correlated with N-deposition. The site with the highest average annual emission (82 μg NO-N m−2 h−1 was a spruce forest in South-Germany (Höglwald receiving an annual N-deposition of 2.9 g m−2. NO emissions close to the detection limit were observed from a pine forest in Finland where the N-deposition was 0.2 g N m−2 a−1. No significant correlation between N2O emission and N-deposition was found. The highest average annual N2O emission (20 μg N2O-N m−2 h−1 was found in an oak forest in the Mátra mountains (Hungary receiving an annual N-deposition of 1.6 g m−2. N2O emission was significantly negatively correlated with the C/N ratio. The difference in N-oxide emissions from soils of coniferous and deciduous forests may partly be explained by differences in N-deposition rates and partly by differences in characteristics of the litter layer and soil. NO was mainly derived from nitrification whereas N2O was mainly derived from denitrification. In general, soil moisture is lower at coniferous sites (at least during spring time and the litter layer of coniferous forests is thick and well aerated favouring nitrification and thus release of NO. Conversely, the higher rates of denitrification in deciduous forests due to a compact and moist litter layer lead to N2O production and NO consumption in the soil. The two factors soil moisture and soil temperature are

Mitigation of nitrous oxide (N2 O) emission from swine wastewater treatment in an aerobic bioreactor packed with carbon fibers.

Science.gov (United States)

Yamashita, Takahiro; Yamamoto-Ikemoto, Ryoko; Yokoyama, Hiroshi; Kawahara, Hirofumi; Ogino, Akifumi; Osada, Takashi

2015-03-01

Mitigation of nitrous oxide (N2 O) emission from swine wastewater treatment was demonstrated in an aerobic bioreactor packed with carbon fibers (CF reactor). The CF reactor had a demonstrated advantage in mitigating N2 O emission and avoiding NOx (NO3  + NO2 ) accumulation. The N2 O emission factor was 0.0003 g N2 O-N/gTN-load in the CF bioreactor compared to 0.03 gN2 O-N/gTN-load in an activated sludge reactor (AS reactor). N2 O and CH4 emissions from the CF reactor were 42 g-CO2 eq/m(3) /day, while those from the AS reactor were 725 g-CO2 eq/m(3) /day. The dissolved inorganic nitrogen (DIN) in the CF reactor removed an average of 156 mg/L of the NH4 -N, and accumulated an average of 14 mg/L of the NO3 -N. In contrast, the DIN in the AS reactor removed an average 144 mg/L of the NH4 -N and accumulated an average 183 mg/L of the NO3 -N. NO2 -N was almost undetectable in both reactors. © 2014 Japanese Society of Animal Science.

Modeling Electron Competition among Nitrogen Oxides Reduction and N₂O Accumulation in Hydrogenotrophic Denitrification

DEFF Research Database (Denmark)

Liu, Yiwen; Ngo, Huu Hao; Guo, Wenshan

2018-01-01

Hydrogenotrophic denitrification is a novel and sustainable process for nitrogen removal, which utilizes hydrogen as electron donor and carbon dioxide as carbon source. Recent studies have shown that nitrous oxide (N2O), a highly undesirable intermediate and potent greenhouse gas, can accumulate...

Preparation, characterization and catalytic behavior of hierachically porous CuO/α-Fe2O3/SiO2 composite material for CO and o-DCB oxidation

Institute of Scientific and Technical Information of China (English)

Xiaodong Ma; Xi Feng; Xuan He; Hongwen Guo; Lu Lü

2011-01-01

Hierachically porous (HP) CuO/α-Fe2O3/SiO2 composite material was fabricated by sol-gel method and multi-hydrothermal processes using HP-SiO2 as support.The resulting material was characterized by N2 adsorption-desorption,X-ray diffraction and scanning electron microscopy.The as-prepared CuO/Fe2O3/HP-SiO2 sample,with α-Fe2O3 and CuO nanocrystals,possessed a co-continuous skeleton,through-macroporous and mesoporous structure.Its catalytic behavior for CO and o-DCB oxidation was investigated.The result showed that CuO/Fe2O3/HP-SiO2 catalyst exhibited high catalytic activity for both CO and o-DCB oxidation,indicating its potential application in combined abatement of CO and chlorinated volatile organic compounds.

Effects of interfacial layer on characteristics of TiN/ZrO2 structures.

Science.gov (United States)

Kim, Younsoo; Kang, Sang Yeol; Choi, Jae Hyoung; Lim, Jae Soon; Park, Min Young; Chung, Suk-Jin; Chung, Jaegwan; Lee, Hyung Ik; Kim, Ki Hong; Kyoung, Yong Koo; Heo, Sung; Yoo, Cha Young; Kang, Ho-Kyu

2011-09-01

To minimize the formation of unwanted interfacial layers, thin interfacial layer (ZrCN layer) was deposited between TiN bottom electrode and ZrO2 dielectric in TiN/ZrO2/TiN capacitor. Carbon and nitrogen were also involved in the layer because ZrCN layer was thermally deposited using TEMAZ without any reactant. Electrical characteristics of TiN/ZrO2/TiN capacitor were improved by insertion of ZrCN layer. The oxidation of TiN bottom electrode was largely inhibited at TiN/ZrCN/ZrO2 structure compared to TiN/ZrO2 structure. While the sheet resistance of TiN/ZrCN/ZrO2 structure was constantly sustained with increasing ZrO2 thickness, the large increase of sheet resistance was observed in TiN/ZrO2 structure after 6 nm ZrO2 deposition. When ZrO2 films were deposited on ZrCN layer, the deposition rate of ZrO2 also increased. It is believed that ZrCN layer acted both as a protection layer of TiN oxidation and a seed layer of ZrO2 growth.

Theoretical study for the reduction of N2O with CO Mediated by alkaline-earth metal oxide cations 2MO+(M=Ca, Sr, Ba)

International Nuclear Information System (INIS)

Zhang Jianhui; Leng Yanli; Wang Yongcheng

2013-01-01

The reaction mechanism of the reaction N 2 O( 0 Σ + ) + CO ( 1 Σ + )→N 2 ( 1 Σ g + ) + CO 2 ( 1 Σ g + ) mediated by alkaline-earth metal oxide cations 2 MO + (m=Ca, Sr, Ba) have been investigated by using the UB3LYP and CCSD (T) levels of theory. The O-atom affinities (OA) testified that only the 2 CaO + can capture O from N 2 O and transfer O to CO is thermodynamically allowed in three ions. The processes can be expressed as channels l and 2 for the reaction of N 2 O and CO mediated by 2 MO + (M=Ca, Sr, Ba). For the former, the main reaction processes in a two-step manner to products, the 2 MO + , as a catalyzer, transports an oxygen atom from N 2 O to CO. For the latter, firstly, the N 2 O interact with the 2 MO + to form IM1, then IM1 interact with the CO to form IM2', along the reaction pathway the intermediate species convert into products 2 1MO + , N 2 and CO 2 . From above results, the following conclusion was drawn. The channel 2 is kinetically and thermodynamically feasible. Our calculated results show the title reactions are accord with the experiment. (authors)

Degradación de recubrimientos ZrO2-CaO/NiAlMo por oxidación isoterma

Directory of Open Access Journals (Sweden)

Utrilla, V.

2006-12-01

Full Text Available This paper analyses the degradation of a ceramic top coating 70%ZrO2 – 30%CaO deposited onto a stainless steel AISI 304 by thermal spray, using Ni-6%Al-5%Mo as overlay coating. These thermal barrier coatings were heat treated for 48, 120 and 288 h at 800 ºC to evaluate the degradation of these materials by isothermal oxidation. The microstructure evolution during oxidation was analysed by environmental scanning electron microscopy, transmission electron microscopy, X ray microanalysis and X ray diffraction. A thermally grown oxide layer was observed between the overlay coating and the ceramic top coating after oxidation. This layer was formed by a mixed Al and Ni oxides.En este trabajo se estudia la degradación de un recubrimiento 70%ZrO2 – 30%CaO crecido por proyección térmica de oxiacetileno sobre un acero inoxidable austenítico AISI 304 y empleando una leación de Ni-6%Al-5%Mo como capa de anclaje. Los recubrimientos se trataron térmicamente en aire a 800 ºC durante 48, 120 y 288 horas para evaluar la degradación de estos materiales por oxidación isotérmica. La evolución de la microestructura de las barreras como consecuencia del proceso de oxidación se analizó mediante microscopía electrónica de barrido ambiental, microscopía electrónica de transmisión, microanálisis de rayos X (EDX y difracción de rayos X. Durante la oxidación de los recubrimientos creció una capa intermedia de óxidos (“thermally grown oxides”, TGO entre el anclaje metálico y el recubrimiento cerámico formada por una mezcla de óxidos de Al y Ni.

The denitrification paradox: The role of O2 in sediment N2O production

Science.gov (United States)

Barnes, Jonathan; Upstill-Goddard, Robert C.

2018-01-01

We designed a novel laboratory sediment flux chamber in which we maintained the headspace O2 partial pressure at preselected values, allowing us to experimentally regulate "in-situ" O2 to evaluate its role in net N2O production by an intertidal estuarine sediment (Tyne, UK). In short-term (30 h) incubations with 10 L of overlying estuarine water (∼3 cm depth) and headspace O2 regulation (headspace: sediment/water ratio ∼9:1), net N2O production was highest at 1.2% O2 (sub-oxic; 32.3 nmol N2O m-2 d-1), an order of magnitude higher than at either 0.0% (anoxic; 2.5 N2O nmol m-2 d-1) or 20.85% (ambient; 2.3 nmol N2O m-2 d-1) O2. In a longer-term sealed incubation (∼490 h) without O2 control, time-dependent behaviour of N2O in the tank headspace was highly non-linear with time, showing distinct phases: (i) an initial period of no or little change in O2 or N2O up to ∼ 100 h; (ii) a quasi-linear, inverse correlation between O2 and N2O to ∼360 h, in which O2 declined to ∼2.1% and N2O rose to ∼7800 natm; (iii) over the following 50 h a slower O2 decline, to ∼1.1%, and a more rapid N2O increase, to ∼12000 natm; (iv) over the next 24 h a slowed O2 decline towards undetectable levels and a sharp fall in N2O to ∼4600 natm; (iv) a continued N2O decrease at zero O2, to ∼3000 natm by ∼ 490 h. These results show clearly that rapid N2O consumption (∼115 nmol m-2 d-1), presumably via heterotrophic denitrification (HD), occurs under fully anoxic conditions and therefore that N2O production, which was optimal for sub-oxic O2, results from other nitrogen transformation processes. In experiments in which we amended sediment overlying water to either 1 mM NH4+ or 1 mM NO3-, N2O production rates were 2-134 nmol N2O m-2 d-1 (NH4+ addition) and 0.4-2.2 nmol N2O m-2 d-1 (NO3- addition). We conclude that processes involving NH4+ oxidation (nitrifier nitrification; nitrifier denitrification; nitrification-coupled denitrification) are principally responsible for N2O

Effect of COD/N ratio on N2O production during nitrogen removal by aerobic granular sludge.

Science.gov (United States)

Velho, V F; Magnus, B S; Daudt, G C; Xavier, J A; Guimarães, L B; Costa, R H R

2017-12-01

N 2 O-production was investigated during nitrogen removal using aerobic granular sludge (AGS) technology. A pilot sequencing batch reactor (SBR) with AGS achieved an effluent in accordance with national discharge limits, although presented a nitrite accumulation rate of 95.79% with no simultaneous nitrification-denitrification. N 2 O production was 2.06 mg L -1 during the anoxic phase, with N 2 O emission during air pulses and the aeration phase of 1.6% of the nitrogen loading rate. Batch tests with AGS from the pilot reactor verified that at the greatest COD/N ratio (1.55), the N 2 O production (1.08 mgN 2 O-N L -1 ) and consumption (up to 0.05 mgN 2 O-N L -1 ), resulted in the lowest remaining dissolved N 2 O (0.03 mgN 2 O-N L -1 ), stripping the minimum N 2 O gas (0.018 mgN 2 O-N L -1 ). Conversely, the carbon supply shortage, under low C/N ratios, increased N 2 O emission (0.040 mgN 2 O-N L -1 ), due to incomplete denitrification. High abundance of ammonia-oxidizing and low abundance of nitrite-oxidizing bacteria were found, corroborating the fact of partial nitrification. A denitrifying heterotrophic community, represented mainly by Pseudoxanthomonas, was predominant in the AGS. Overall, the AGS showed stable partial nitrification ability representing capital and operating cost savings. The SBR operation flexibility could be advantageous for controlling N 2 O emissions, and extending the anoxic phase would benefit complete denitrification in cases of low C/N influents.

Biologically fixed N2 as a source for N2O production in a grass–clover mixture, measured by 15N2 (erratum i vol. 74 p. 203)

DEFF Research Database (Denmark)

Carter, Mette Sustmann; Ambus, P.

2006-01-01

The contribution of biologically fixed dinitrogen (N-2) to the nitrous oxide (N2O) production in grasslands is unknown. To assess the contribution of recently fixed N-2 as a source of N2O and the transfer of fixed N from clover to companion grass, mixtures of white clover and perennial ryegrass...

Resolution of 1-n-butyl-3-methyl-3-phospholene 1-oxide with TADDOL derivatives and calcium salts of O,O'-Dibenzoyl-(2R,3R)- or O,O'-di-p-toluoyl-(2R,3R)-tartaric acid.

Science.gov (United States)

Bagi, Péter; Fekete, András; Kállay, Mihály; Hessz, Dóra; Kubinyi, Miklós; Holczbauer, Tamás; Czugler, Mátyás; Fogassy, Elemér; Keglevich, György

2014-03-01

The resolution methods applying (-)-(4R,5R)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyldioxolane ("TADDOL"), (-)-(2R,3R)-α,α,α',α'-tetraphenyl-1,4-dioxaspiro[4.5]decan-2,3-dimethanol ("spiro-TADDOL"), as well as the acidic and neutral Ca(2+) salts of (-)-O,O'-dibenzoyl- and (-)-O,O'-di-p-toluoyl-(2R,3R)-tartaric acid were extended for the preparation of 1-n-butyl-3-methyl-3-phospholene 1-oxide in optically active form. In one case, the intermediate diastereomeric complex could be identified by single-crystal X-ray analysis. The absolute P-configuration of the enantiomers of the phospholene oxide was also determined by comparing the experimentally obtained and calculated CD spectra. © 2014 Wiley Periodicals, Inc.

Pyrrolic-N-doped graphene oxide/Fe2O3 mesocrystal nanocomposite: Efficient charge transfer and enhanced photo-Fenton catalytic activity

Science.gov (United States)

Liu, Bing; Tian, Lihong; Wang, Ran; Yang, Jinfeng; Guan, Rong; Chen, Xiaobo

2017-11-01

Though α-Fe2O3 has attracted much attention in photocatalytic or Fenton-catalytic degradation of organic contaminants, its performance is still unsatisfactory due to fast recombination of electrons and holes in photocatalytic process and the difficult conversion of Fe(II) and Fe(III) in Fenton reaction. Herein, a pyrrolic N-doped graphene oxide/Fe2O3 mesocrystal (NG-Fe2O3) nanocomposite with good distribution is synthesized by a simple solvothermal method and adjusting the oxygen-containing groups on graphene oxide. The morphology of NG-Fe2O3 contributes to a relatively large BET surface area and an intimate contact between NG and Fe2O3. These two important factors along with the excellent electro-conductivity of pyrrolic-N doped GO result in the efficient separation of electron-hole pairs and fast conversion of Fe(II)and Fe(III) in photo-Fenton synergistic reaction. Thus, a remarkably improved photo-Fenton catalytic activity of NG-Fe2O3 is obtained. The degrading rate on methyl blue increases by 1.5 times and the conversion rate of glyphosate increases by 2.3 times under visible light irradiation, compared to pristine α-Fe2O3 mesocrystals.

The Nitrous Oxide (N2O) Budget: Constraints from Atmospheric Observations and Models

Science.gov (United States)

Tian, H.; Thompson, R.; Canadell, J.; Winiwarter, W.; Tian, H.; Thompson, R.; Prather, M. J.

2017-12-01

The increasing global abundance of N2O poses a threat to human health and society over this coming century through both climate change and ozone depletion. In the sense of greenhouse gases, N2O ranks third behind CO2 and CH4. In the sense of ozone depletion, N2O stands alone. In order to identify the cause of these increases and hopefully reverse them, we need to have a thorough understanding of the sources and sinks (a.k.a. the budget) of N2O and how they can be altered. A bottom-up approach to the budget evaluates individual biogeochemical sources of N2O from the land and ocean; whereas, a top-down approach uses atmospheric observations of the variability, combined with modeling of the atmospheric chemistry and transport, to infer the magnitude of sources and sinks throughout the Earth system. This paper reviews top-down approaches using atmospheric data; a similar top-down approach can be taken with oceanic measurements of N2O, but is not covered here. Stratospheric chemistry is the predominant loss of N2O, and here we review how a merging of new measurements with stratospheric chemistry models is able to provide a constrained budget for the global N2O sink. N2O surface sources are transported and mixed throughout the atmosphere, providing positive anomalies in the N2O abundance (mole fraction of N2O with respect to dry air); while N2O-depleted air from the stratosphere provides negative anomalies. With accurate atmospheric transport models, including for stratosphere-troposphere exchange, the observed tropospheric variability in N2O is effectively a fingerprint of the location and magnitude of sources. This inverse modeling of sources is part of the top-down constraints and is reviewed here.

Facile one-pot construction of α-Fe_2O_3/g-C_3N_4 heterojunction for arsenic removal by synchronous visible light catalysis oxidation and adsorption

International Nuclear Information System (INIS)

Sun, Suwen; Ji, Chunnuan; Wu, Lingling; Chi, Shenghua; Qu, Rongjun; Li, Yan; Lu, Yangxiao; Sun, Changmei; Xue, Zhongxin

2017-01-01

α-Fe_2O_3/g-C_3N_4 composites with heterojunction were prepared by facile one-pot synthesis using ferric chloride and dicyandiamide as precursors. The newly formed composites were applied to remove arsenic from aqueous solution for the first time through synchronous visible light catalysis oxidation and adsorption. α-Fe_2O_3/g-C_3N_4 composites were characterized by wide-angle X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectroscopy, and BET surface analysis. Under visible light irradiation, As(III) was oxidized to As(V) efficiently on the surface of α-Fe_2O_3/g-C_3N_4. In addition, the oxidized arsenic could be adsorbed in situ, resulting in the effective arsenic removal. The enhancement of photocatalytic activity the composites was attributed to the construction of heterojunction between α-Fe_2O_3 and g-C_3N_4. A possible oxidation mechanism of the as-composites for As(III) under visible light irradiation was also elucidated. - Highlights: • α-Fe_2O_3/g-C_3N_4 composites with heterojunction was prepared by facile one-pot synthesis. • The photocatalytic activity of α-Fe_2O_3/g-C_3N_4 composites under visible light irradiation for As(III) was evaluated. • Synchronous visible light catalysis oxidation and adsorption were achieved for the removal of arsenic. • The reasonable oxidation mechanism of the composites for As(III) under visible light irradiation was investigated.

Mild and Efficient Deoxygenation of Amine-N-Oxides with FeCl3·6H2O-Indium System under Ultrasonication

International Nuclear Information System (INIS)

Yoo, Byung Woo; Hwang, Sun Kyun; Kim, Dong Yoon; Choi, Jin Woo; Kang, Sang Ook; Yoo, Byoung Seung; Choi, Kyung Il; Kim, Joong Hyup

2004-01-01

We believe that the mild and efficient method described here will present an attractive alternative to the existing methods available for the reduction of amine-N-oxides to the corresponding amines. Further investigations of FeCl 3 ·6H 2 O/In system as reducing agent in organic synthesis are currently in progress. The deoxygenation of amine-N-oxides to amines in the presence of other functional groups is an important transformation in the synthesis of nitrogenous aromatic heterocycles. Many reagents have been employed for the deoxygenation of amine-N-oxides, including agents such as: low-valent titanium, phosphorous and sulphur compounds, tributyltin hydride, Pd/C, tetrathiomolybdate, SmI 2 , indium/NH 4 Cl. Recently we reported that Cp 2 TiCl 2 /In system could be used for the deoxygenation of various amine-N-oxides

Band offsets of n-type electron-selective contacts on cuprous oxide (Cu{sub 2}O) for photovoltaics

Energy Technology Data Exchange (ETDEWEB)

Brandt, Riley E., E-mail: rbrandt@alum.mit.edu, E-mail: buonassisi@mit.edu; Lee, Yun Seog; Buonassisi, Tonio, E-mail: rbrandt@alum.mit.edu, E-mail: buonassisi@mit.edu [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Young, Matthew; Dameron, Arrelaine; Teeter, Glenn [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Park, Helen Hejin; Chua, Danny; Gordon, Roy G. [Harvard University, Cambridge, Massachusetts 02139 (United States)

2014-12-29

The development of cuprous oxide (Cu{sub 2}O) photovoltaics (PVs) is limited by low device open-circuit voltages. A strong contributing factor to this underperformance is the conduction-band offset between Cu{sub 2}O and its n-type heterojunction partner or electron-selective contact. In the present work, a broad range of possible n-type materials is surveyed, including ZnO, ZnS, Zn(O,S), (Mg,Zn)O, TiO{sub 2}, CdS, and Ga{sub 2}O{sub 3}. Band offsets are determined through X-ray photoelectron spectroscopy and optical bandgap measurements. A majority of these materials is identified as having a negative conduction-band offset with respect to Cu{sub 2}O; the detrimental impact of this on open-circuit voltage (V{sub OC}) is evaluated through 1-D device simulation. These results suggest that doping density of the n-type material is important as well, and that a poorly optimized heterojunction can easily mask changes in bulk minority carrier lifetime. Promising heterojunction candidates identified here include Zn(O,S) with [S]/[Zn] ratios >70%, and Ga{sub 2}O{sub 3}, which both demonstrate slightly positive conduction-band offsets and high V{sub OC} potential. This experimental protocol and modeling may be generalized to evaluate the efficiency potential of candidate heterojunction partners for other PV absorbers, and the materials identified herein may be promising for other absorbers with low electron affinities.

Market Analysis DeN2O. Market potential for reduction of N2O emissions at nitric acid facilities

International Nuclear Information System (INIS)

Smit, A.W.; Gent, M.M.C.; Van den Brink, R.W.

2001-05-01

ECN has developed a technique for the removal of nitrous oxide (N2O) from the tail gases of a nitric acid plant. The aim of this project was to make an assessment of the market opportunities of this technique. To this end a study was made of the relevant international regulations and agreements on the field of climate policy. The formulation of an international greenhouse gas policy and concomitant flexible mechanisms is a prerequisite for the market introduction of any N2O abatement technique. The available techniques and techniques in development for N2O abatement in the nitric acid industry are described and the strengths and weaknesses are given. Furthermore, the costs per ton CO2 equivalents removed are estimated. Direct decomposition of N2O (either in the NH3 combustion reactor or downstream the absorber) are the most cost efficient techniques. Finally, the number and sizes of nitric acid plants in Europe and the developments in the fertiliser market are described. The current difficult fertiliser market makes the nitric acid producers reluctant to invest in N2O abatement technologies

TiO2, SiO2 and ZrO2 Nanoparticles Synergistically Provoke Cellular Oxidative Damage in Freshwater Microalgae

Directory of Open Access Journals (Sweden)

Yinghan Liu

2018-02-01

Full Text Available Metal-based nanoparticles (NPs are the most widely used engineered nanomaterials. The individual toxicities of metal-based NPs have been plentifully studied. However, the mixture toxicity of multiple NP systems (n ≥ 3 remains much less understood. Herein, the toxicity of titanium dioxide (TiO2 nanoparticles (NPs, silicon dioxide (SiO2 NPs and zirconium dioxide (ZrO2 NPs to unicellular freshwater algae Scenedesmus obliquus was investigated individually and in binary and ternary combination. Results show that the ternary combination systems of TiO2, SiO2 and ZrO2 NPs at a mixture concentration of 1 mg/L significantly enhanced mitochondrial membrane potential and intracellular reactive oxygen species level in the algae. Moreover, the ternary NP systems remarkably increased the activity of the antioxidant defense enzymes superoxide dismutase and catalase, together with an increase in lipid peroxidation products and small molecule metabolites. Furthermore, the observation of superficial structures of S. obliquus revealed obvious oxidative damage induced by the ternary mixtures. Taken together, the ternary NP systems exerted more severe oxidative stress in the algae than the individual and the binary NP systems. Thus, our findings highlight the importance of the assessment of the synergistic toxicity of multi-nanomaterial systems.

The diversity of the N2O reducers matters for the N2O:N2 denitrification end-product ratio across an annual and a perennial cropping system.

Science.gov (United States)

Domeignoz-Horta, Luiz A; Spor, Aymé; Bru, David; Breuil, Marie-Christine; Bizouard, Florian; Léonard, Joël; Philippot, Laurent

2015-01-01

Agriculture is the main source of terrestrial emissions of N2O, a potent greenhouse gas and the main cause of ozone layer depletion. The reduction of N2O into N2 by microorganisms carrying the nitrous oxide reductase gene (nosZ) is the only biological process known to eliminate this greenhouse gas. Recent studies showed that a previously unknown clade of N2O-reducers was related to the capacity of the soil to act as an N2O sink, opening the way for new strategies to mitigate emissions. Here, we investigated whether the agricultural practices could differently influence the two N2O reducer clades with consequences for denitrification end-products. The abundance of N2O-reducers and producers was quantified by real-time PCR, and the diversity of both nosZ clades was determined by 454 pyrosequencing. Potential N2O production and potential denitrification activity were used to calculate the denitrification gaseous end-product ratio. Overall, the results showed limited differences between management practices but there were significant differences between cropping systems in both the abundance and structure of the nosZII community, as well as in the [rN2O/r(N2O+N2)] ratio. More limited differences were observed in the nosZI community, suggesting that the newly identified nosZII clade is more sensitive than nosZI to environmental changes. Potential denitrification activity and potential N2O production were explained mainly by the soil properties while the diversity of the nosZII clade on its own explained 26% of the denitrification end-product ratio, which highlights the importance of understanding the ecology of this newly identified clade of N2O reducers for mitigation strategies.

Photoactivity of N-doped ZnO nanoparticles in oxidative and reductive reactions

Science.gov (United States)

Oliveira, Jéssica A.; Nogueira, André E.; Gonçalves, Maria C. P.; Paris, Elaine C.; Ribeiro, Caue; Poirier, Gael Y.; Giraldi, Tania R.

2018-03-01

N-doped ZnO is a prospective material for photocatalytic reactions. However, only oxidative paths are well investigated in the literature. This paper describes a comparative study about ZnO and ZnO:N potential for oxidative and reductive reactions, probed by rhodamine B dye photodegradation and CO2 photoreduction. The materials were prepared by the polymeric precursor method, using urea as a nitrogen source, and different heat treatments were used to observe their effects on surface decontamination, crystallinity, particle sizes and shapes, and photocatalytic performance. ZnO and ZnO:N presented a wurtzite crystalline structure and nanometric-scale particles. Samples submitted to higher temperatures showed lower specific surface areas, but higher crystallinity and lower contents of species adsorbed on their surfaces. On the other hand, the photocatalysts annealed in shorter times presented smaller crystallite sizes and lower crystallinity. These factors influenced the photoactivity in both conditions, i.e., oxidation and reduction reactions, under the ultraviolet and visible light, indicating that structural factors influenced the adequate charge separation and consequent photocatalytic activity since the as-synthesized samples were versatile photocatalysts in both redox reactions.

Emission of N2O from production of energy crops

International Nuclear Information System (INIS)

Lind, A.M.; Joergensen, U.; Maag, M.

1995-01-01

The contribution of N 2 O (nitrous oxide) to the greenhouse effect has been increasing during the latest years. The increase in the contribution from N 2 O is partly caused by increasing emission from soil, mainly due to human activity, and partly as a result of an increasing radiatively greenhouse effect as relative to CO 2 according to general recalculations and reevaluation. The contribution from agriculture is directly from cultivated soil as well as indirectly (production of fertilizer and food). Formation of N 2 O in soil is mainly dependent on variations in content of soil water, oxygen state, and on availability of organic matter. Soil type and cropping are also important. The factors are interrelated, and their influence on the two N 2 O-forming processes, nitrification and denitrification, are very fluctuating resulting in large variations (spatial and temporal) for measurements of the emission in field. In the present paper, the state of knowledge is given for the emission of nitrous oxide from cultivated soil as well as from different types of natural ecosystems. Significant differences between N 2 O-emission from different annual crops cannot be expected. Based on Danish measurements of N 2 O-emission (spring barley, winter wheat and spring rape) the net displacement of CO 2 is calculated. The deduction of N 2 O varied from being double as high as the deduction for the production dependent CO 2 -emission to a lot less than that. There was a marked influence of the yields of the specific crops in the actual measuring years on the relative effect of the N 2 O deduction on the net-displacement of CO 2 . (EG)

Oxidation reactivity channels for 2-(pyridin-2-yl)-N,N-diphenylacetamides

Energy Technology Data Exchange (ETDEWEB)

Pailloux, Sylvie; Binyamin, Iris; Deck, Lorraine M.; Rapko, Brian M.; Hay, Benjamin P.; Duesler, Eileen N.; Paine, Robert T.

2007-11-01

Synthetic routes to 2-(pyridin-2-yl)-N,N-diphenylacetamide and 2-(6-methylpyridin-2-yl)-N,N-diphenylacetamide are described along with results from the chemical oxidation of these compounds with peracetic acid, m-chloroperbenzoic acid, and OXONE. In each case, oxidations generate four products in varying amounts depending on the oxidant and reaction conditions. Each product has been characterized by spectroscopic methods and the molecular structures of several of the new compounds have been confirmed by X-ray crystallography.

Determination of the oxidation mechanism to Cd Te obtained by rf reactive magnetron sputtering in a plasma of Ar-N{sub 2}O; Determinacion del mecanismo de oxigenacion del CdTe obtenido por rf sputtering reactivo con magnetron en un plasma de Ar-N{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Caballero B, F.; Zapata N, A.; Bartolo P, P.; Castro R, R.; Zapata T, M.; Cauich, W.; Pena, J.L. [Departamento de Fisica Aplicada, Centro deInvestigacion y de Estudios Avanzados, Instituto Politecnico Nacional, Unidad Merida, Apartado postal 73, Cordemex, 97310 Merida, Yucatan (Mexico)

1998-12-31

In this work we did studies to determinate the oxidation site and incorporation mechanism of oxygen to Cd Te, when preparing Cd Te:O thin films by r f reactive magnetron sputtering, using a Cd Te target and a controlled plasma of Ar-N{sub 2}O. We study the influence in the oxygen content in films due to the variation of N{sub 2}O partial pressure, plasma power and substrate position. We monitored the process in situ by mass spectrometry to determinate the variation of present compounds when varying the N{sub 2}O partial pressure and plasma power. Thin films composition was determined by Auger electron spectroscopy and their structure by X-ray diffraction. We demonstrate that oxygen incorporation has place mainly in the substrate, forming an amorphous Cd Te:O film. We found that exists Cd Te oxidation without using nitrous oxide, may be due to residual atmosphere. We demonstrate that Cd Te oxidation depends on nitrous oxide partial pressure and plasma power. We found that deposition rate of Cd Te:O thin films depend on nitrous oxide interaction with Cd Te in the target and on the chamber walls. We propose a reaction mechanism to explain the oxygen incorporation to Cd Te. (Author)

Facile Synthesis and Characterization of N-Doped TiO2 Photocatalyst and Its Visible-Light Activity for Photo-Oxidation of Ethylene

Directory of Open Access Journals (Sweden)

Yu-Hao Lin

2015-01-01

Full Text Available A facile wet chemical method was adopted for preparing highly photoactive nitrogen doped TiO2 (N-TiO2 powders with visible responsive capability, which could be achieved by the hydrolysis of titanium isopropoxide (TTIP in the ammonium hydroxide precursor solution in various concentrations and then calcined at different temperatures. The N-TiO2 powders were characterized, and the photocatalytic activity was evaluated for the photocatalytic oxidation of ethylene gas under visible light irradiation to optimize the synthesizing conditions of N-TiO2 catalyst. The N-TiO2 photocatalytic powders were calcined in a range of temperatures from 300 to 600°C and obviously found to have greater photocatalytic activities than commercial TiO2 P25. The strong absorption in the visible light region could be ascribed to good crystallization and adapted sinter temperature of as prepared sample. XPS test demonstrated that the N was doped into TiO2 lattice and made an interstitial formation (Ti-O-N, and N doping also retarded the phase transformation from anatase to rutile as well. The N-TiO2 catalyst prepared with 150 mL ammonium hydroxide added and calcined at 500°C showed the best photocatalytic activity. The experimental results also proved the enhanced photoactivity of N-TiO2 material depends on the synthesizing conditions.

Emission control of odour and N{sub 2}O from a mechanical biological pretreatment; Geruchsstoffe und N{sub 2}O im Abgas einer mechanisch-biologischen Abfallbehandlungsanlage

Energy Technology Data Exchange (ETDEWEB)

Cuhls, C.; Clemens, J. [Gesellschaft fuer Wissenstransfer, Bonn (Germany); Stockinger, J.; Doedens, H. [Hannover Univ. (Germany). Inst. fuer Siedlungswasserwirtschaft und Abfalltechnik

2002-04-01

Within the mechanical biological pretreatment (MBP) the aerobic treatment of waste is the major source of gaseous emissions. So far, the exhaust air has been treated by biofilters. But biofilters may act as a source of nitric and nitrous oxide (NO and N{sub 2}O) formed by excess ammonia (NH{sub 3}) and cannot oxidize methane (CH{sub 4}). As a consequence, biofilters may not be suitable to match the demands of the 30. Immission Ordinance (BImSchV). Thermal oxidation is able to keep total carbon below the new thresholds. NH{sub 3} is transformed to NO and NO{sub 2} uring the thermal oxidation. Depending on the oxidation temperature N{sub 2}O may be formed. When exhaust air was treated by scrubbing with mineral acid, N{sub 2}O, NO{sub x} and odour emissions were reduced. Four different teams measured odour concentrations in the treated air. There were differences of factor 10 between the results even when the teams analysed the same sample with the same olfactometer. These results suggest to improve the methodology of odour measurements at least for this application. (orig.)

Evaluating four N2O emission algorithms in RZWQM2 in response to N rate on an irrigated corn field

Science.gov (United States)

Nitrous oxide (N2O) emissions from agricultural soils are major contributors to greenhouse gases. Correctly assessing the effects of the interactions between agricultural practices and environmental factors on N2O emissions is required for better crop and nitrogen (N) management. We used an enhanced...

Isotopic discrimination during nitrous oxide loss processes: An important piece of the N2O global atmospheric budget

International Nuclear Information System (INIS)

Rahn, T.; Wahlen, M.; Zhang Hui; Blake, G.

2002-01-01

Nitrous oxide plays an important role in greenhouse forcing and stratospheric ozone regulation. It is destructed in the stratosphere mainly by UV photolysis. Laboratory studies of N 2 O-N 2 mixtures irradiated at 193 and 207 nm reveal a significant enrichment of the residual heavy nitrous oxide isotopomers. The isotopic signatures are well described by an irreversible Rayleigh distillation process, with large enrichment factors of ε 15,18 (193 nm) = -18.4, -14.5 per mil and ε 15,18 (207 nm) = -48.7, -46.0 per mil. These results, when combined with diffusive mixing processes might help to explain the stratospheric enrichments previously observed. (author)

C=C bond cleavage on neutral VO3(V2O5)n clusters.

Science.gov (United States)

Dong, Feng; Heinbuch, Scott; Xie, Yan; Bernstein, Elliot R; Rocca, Jorge J; Wang, Zhe-Chen; Ding, Xun-Lei; He, Sheng-Gui

2009-01-28

The reactions of neutral vanadium oxide clusters with alkenes (ethylene, propylene, 1-butene, and 1,3-butadiene) are investigated by experiments and density function theory (DFT) calculations. Single photon ionization through extreme ultraviolet radiation (EUV, 46.9 nm, 26.5 eV) is used to detect neutral cluster distributions and reaction products. In the experiments, we observe products (V(2)O(5))(n)VO(2)CH(2), (V(2)O(5))(n)VO(2)C(2)H(4), (V(2)O(5))(n)VO(2)C(3)H(4), and (V(2)O(5))(n)VO(2)C(3)H(6), for neural V(m)O(n) clusters in reactions with C(2)H(4), C(3)H(6), C(4)H(6), and C(4)H(8), respectively. The observation of these products indicates that the C=C bonds of alkenes can be broken on neutral oxygen rich vanadium oxide clusters with the general structure VO(3)(V(2)O(5))(n=0,1,2...). DFT calculations demonstrate that the reaction VO(3) + C(3)H(6) --> VO(2)C(2)H(4) + H(2)CO is thermodynamically favorable and overall barrierless at room temperature. They also provide a mechanistic explanation for the general reaction in which the C=C double bond of alkenes is broken on VO(3)(V(2)O(5))(n=0,1,2...) clusters. A catalytic cycle for alkene oxidation on vanadium oxide is suggested based on our experimental and theoretical investigations. The reactions of V(m)O(n) with C(6)H(6) and C(2)F(4) are also investigated by experiments. The products VO(2)(V(2)O(5))(n)C(6)H(4) are observed for dehydration reactions between V(m)O(n) clusters and C(6)H(6). No product is detected for V(m)O(n) clusters reacting with C(2)F(4). The mechanisms of the reactions between VO(3) and C(2)F(4)/C(6)H(6) are also investigated by calculations at the B3LYP/TZVP level.

Soil invertebrate fauna affect N2O emissions from soil

NARCIS (Netherlands)

Kuiper, I.; Deyn, de G.B.; Thakur, M.P.; Groenigen, van J.W.

2013-01-01

Nitrous oxide (N2O) emissions from soils contribute significantly to global warming. Mitigation of N2O emissions is severely hampered by a lack of understanding of its main controls. Fluxes can only partly be predicted from soil abiotic factors and microbial analyses – a possible role for soil fauna

Reduced graphene oxide wrapped Cu2O supported on C3N4: An efficient visible light responsive semiconductor photocatalyst

Directory of Open Access Journals (Sweden)

S. Ganesh Babu

2015-10-01

Full Text Available Herein, Cu2O spheres were prepared and encapsulated with reduced graphene oxide (rGO. The Cu2O–rGO–C3N4 composite covered the whole solar spectrum with significant absorption intensity. rGO wrapped Cu2O loading caused a red shift in the absorption with respect to considering the absorption of bare C3N4. The photoluminescence study confirms that rGO exploited as an electron transport layer at the interface of Cu2O and C3N4 heterojunction. Utmost, ∼2 fold synergistic effect was achieved with Cu2O–rGO–C3N4 for the photocatalytic reduction of 4-nitrophenol to 4-aminophenol in comparison with Cu2O–rGO and C3N4. The Cu2O–rGO–C3N4 photocatalyst was reused for four times without loss in its activity.

Efectos de fotodegradación propiciados por recubrimientos de TiO2 y TiO2-SiO2 obtenidos por Sol-Gel

Directory of Open Access Journals (Sweden)

Rodriguez Paez, J. E.

2008-10-01

Full Text Available Photodegradation effect is widely used for water purification this contributes to preservation and protection of environment. Titanium oxide, (TiO2, is a compound that shows up this phenomenon. TiO2 is a semiconductor which may degradate pollutants through of a oxidation process. It permit the treatment of the residual water. It this work we has conformed coatings of TiO2 y TiO2-SiO2, utilized Sol-Gel method and investigated the degradation of the blue Methylene. For this, we introduced these coatings in the blue methylene solution which was illuminated with radiation of λ=365nm to activate its photocatilist properties. The structures of the coatings were characterized using Atomic Force Microscopy (AFM and X-ray Photoelectron Spectroscopy (XPS.El efecto de fotodegradación es ampliamente utilizado para la purificación del agua, acción que contribuye a la conservación y protección del medio ambiente; el óxido de titanio (TiO2 es uno de los semiconductores que pueden degradar contaminantes mediante procesos de oxidación, lo que lo hace apto para el tratamiento de aguas residuales. En este trabajo se conformaron recubrimientos de TiO2 y TiO2-SiO2, por el método Sol-Gel, y se estudio la degradación que experimentaba una solución de azul de metileno al introducirle estos recubrimientos e iluminarlos con una radiación de λ=365nm para activar su propiedad fotocatalítica. Los recubrimientos fueron caracterizados microestructuralmente utilizando Microscopía de Fuerza Atómica (MFA y Espectroscopía de Fotoelectrones de rayos X (XPS. Los resultados obtenidos de los ensayos de fotodegradación indican que los recubrimientos con una cantidad pequeña de silicio presentan un mayor efecto de fotodegradación indicando que el silicio puede generar puntos de anclaje que facilitan las reacciones de fotocatálisis. Por otro lado, la formación de centros activos, constituidos principalmente por carbono, también contribuyeron al desarrollo de estas

Nitrous Oxide (N2O) Emissions from California based on 2010 CalNex Airborne Measurements

Science.gov (United States)

Xiang, B.; Miller, S.; Kort, E. A.; Santoni, G. W.; Daube, B.; Commane, R.; Angevine, W. M.; Ryerson, T. B.; Trainer, M.; Andrews, A. E.; Nehrkorn, T.; Tian, H.; Wofsy, S. C.

2012-12-01

Nitrous oxide (N2O) is an important gas for climate and for stratospheric chemistry, with an atmospheric lifetime exceeding 100 years. Global concentrations have increased steadily since the 18th century, apparently due to human-associated emissions, principally from application of nitrogen fertilizers. However, quantitative studies of agricultural emissions at large spatial scales are lacking, inhibited by the difficulty of measuring small enhancements of atmospheric concentrations. Here we derive regional emission rates for N2O in the Central Valley of California, based on analysis of in-situ airborne atmospheric observations collected using a quantum cascade laser spectrometer. The data were obtained on board the NOAA P-3 research aircraft during the CalNex (California Research at the Nexus of Air Quality and Climate Change) program in May and June, 2010. We coupled WRF (Weather Research and Forecasting) model to STILT (Stochastic Time-Inverted Lagrangian Transport) to link our in-situ observations to surface emissions, and then used a variety of statistical methods to identify source areas and to extract optimized emission rates from the inversion. Our results support the view that fertilizer application is the largest source of N2O in the Central Valley. But the spatial distribution of derived surface emissions, based on California land use and activity maps, was very different than indicated in the leading emissions inventory (EDGAR 4.0), and our estimated total emission flux of N2O for California during the study period was 3 - 4 times larger than EDGAR and other inventories.

Growth and characterization of p-Cu2O/n-ZnO nanorod heterojunctions prepared by a two-step potentiostatic method

International Nuclear Information System (INIS)

Jeong, Yoon Suk; Kim, Hyunghoon; Lee, Ho Seong

2013-01-01

Highlights: •p-Cu 2 O/n-ZnO heterostructures were grown by a two-step potentiostatic method. •The high-quality p-Cu 2 O/n-ZnO nanorod heterojunctions were obtained only at relatively high temperatures of 90 and 100 °C. •p-Cu 2 O/n-ZnO heterojunctions exhibited a well-defined p–n diode characteristic. -- Abstract: p-Cu 2 O/n-ZnO nanorod heterojunctions were fabricated by a two-step process. The process was performed with potentiostatic deposition of n-ZnO nanorods on conductive indium-tin-oxide (ITO) glasses followed by potentiostatic deposition of p-Cu 2 O to form p-Cu 2 O/n-ZnO nanorod heterojunctions. The deposition condition required to form the cuprous oxide layer affected significantly the formation and microstructure of the p-Cu 2 O/n-ZnO nanorod heterojunctions. In particular, the high-quality p-Cu 2 O/n-ZnO nanorod heterojunctions were obtained only at relatively high temperatures of 90 and 100 °C. The p-Cu 2 O/n-ZnO nanorod heterojunctions exhibited a well-defined p–n diode characteristic with an ideality factor of about 4.3

Mixed oxides forming in CdO-OsO2 and PbO-OsO2 systems

International Nuclear Information System (INIS)

Shaplygin, I.S.; Lazarev, V.B.

1978-01-01

The formation of mixed oxides in systems CdO-OsO 2 and PbO-OsO 2 was studied by derivatography, X-ray phase analysis, and IR spectroscopy. It was established that in the system CdO-OsO 2 cubic phases of Cdsub(2)Ossub(2)Osub(6.7) and Cdsub(2)Ossub(2)Osub(7.2) with a pyrochlor-type structure, as well as new compounds with the structure of rhombic perovskite CdOsO 3 and Cd(Cdsub(0.5)Ossub(0.5))Osub(3) containing osmium in the formal degree of oxidation +4 and +6, respectively, are formed. The thermal stability of the compounds obtained was studied and their electrical properties determined

Visible-light-driven N-(BiO)2CO3/Graphene oxide composites with improved photocatalytic activity and selectivity for NOx removal

Science.gov (United States)

Chen, Meijuan; Huang, Yu; Yao, Jie; Cao, Jun-ji; Liu, Yuan

2018-02-01

N-doped (BiO)2CO3 (NBOC)/graphene oxide (GO) composite obtained from three-dimensional hierarchical microspheres is successfully synthesized by one-pot hydrothermal method for the first time. In this synthesis, citrate ion plays a critical role in N doping. The obtained samples are used to degrade gaseous nitrogen oxides (NOx) at parts-per-billion (ppb) level under visible-light irradiation. NBOC-GO composite with 1.0 wt% graphene oxide (GO) displays the highest photocatalytic NO removal efficiency, which is 4.3 times higher than that of pristine (BiO)2CO3. Moreover, NBOC-GO composite significantly inhibits toxic NO2 intermediate production, indicating its high selectivity for NO conversion. Compared with regular GO, N doping considerably improves the catalytic performance of NBOC-GO composite, which increases NO removal by 74.6% and fully inhibits NO2 generation. The improved photocatalytic activity is mainly ascribed to extended optical absorption ability and enhanced separation efficiency of photogenerated charge carriers over NBOC-GO composite. Both results of electron spin resonance and theoretical analysis of band structure indicate that NO removal is dominated by oxidation with rad OH and rad O2- radicals. The photocatalytic activity improvement mechanism over the NBOC-GO composite is proposed accordingly based on systematic characterizations. This study demonstrates a feasible route to fabricating Bi-containing composites with high selectivity and stability for air pollution control and provides a new insight into the associated photocatalytic mechanisms.

A simple way to prepare reduced graphene oxide nanosheets/Fe2O3-Pd/N-doped carbon nanosheets and their application in catalysis.

Science.gov (United States)

Yao, Tongjie; Zhang, Junshuai; Zuo, Quan; Wang, Hao; Wu, Jie; Zhang, Xiao; Cui, Tieyu

2016-04-15

The catalysts with Pd and γ-Fe2O3 nanoparticles embedded between reduced graphene oxide nanosheets (rGS) and N-doped carbon nanosheets (NCS) were prepared through a two-step method. Firstly, graphene oxide nanosheets (GS)/prussian blue (PB)-Pd/polypyrrole (PPy) composites were synthesized by using pyrrole monomer as reductant, K3Fe(CN)6 and PdCl2 as oxidants in the presence of GS via a redox reaction. Subsequently, the as-obtained GS/PB-Pd/PPy composites were calcinated in N2 atmosphere. During the heat-treatment, carbonization of PPy to NCS, conversion of nonmagnetic PB to magnetic γ-Fe2O3 nanoparticles, and reduction of GS to rGS were finished, simultaneously. rGS/Fe2O3-Pd/NCS composites exhibited good catalytic activity toward reduction of 4-nitrophenol. The rate constant k and turnover frequency were calculated and compared with recent reports. Owing to γ-Fe2O3 nanoparticles, the rGS/Fe2O3-Pd/NCS composites could be quickly separated by magnet and reused without obvious decrease in activity. Copyright © 2016 Elsevier Inc. All rights reserved.

Determining oxide trapped charges in Al2O3 insulating films on recessed AlGaN/GaN heterostructures by gate capacitance transients measurements

Science.gov (United States)

Fiorenza, Patrick; Greco, Giuseppe; Schilirò, Emanuela; Iucolano, Ferdinando; Lo Nigro, Raffaella; Roccaforte, Fabrizio

2018-05-01

This letter presents time-dependent gate-capacitance transient measurements (C–t) to determine the oxide trapped charges (N ot) in Al2O3 films deposited on recessed AlGaN/GaN heterostructures. The C–t transients acquired at different temperatures under strong accumulation allowed to accurately monitor the gradual electron trapping, while hindering the re-emission by fast traps that may affect conventional C–V hysteresis measurements. Using this method, an increase of N ot from 2 to 6 × 1012 cm‑2 was estimated between 25 and 150 °C. The electron trapping is ruled by an Arrhenius dependence with an activation energy of 0.12 eV which was associated to points defects present in the Al2O3 films.

N-TiO2/gamma-Al2O3 granules: preparation, characterization and photocatalytic activity for the degradation of 2,4-dichlorophenol.

Science.gov (United States)

Huang, Donggen; Xie, Wenfa; Tu, Zhibin; Zhang, Feng; Quan, Shuiqing; Liu, Lei

2013-01-01

Nitrogen doping TiO2 and gamma-Al2O3 composite oxide granules (N-TiO2/gamma-Al2O3) were prepared by co-precipitation/oil-drop/calcination in gaseous NH3 process using titanium sulphate and aluminum nitrate as raw materials. After calcination at 550 degrees C in NH3 atmosphere, the composite granules showed anatase TiO2 and gamma-Al2O3 phases with the granularity of 0.5-1.0 mm. The anatase crystallite size of composite granules was range from 3.5-25 nm calculated from XRD result. The UV-Vis spectra and N 1s XPS spectra indicated that N atoms were incorporated into the TiO2 crystal lattice. The product granules could be used as a photocatalyst in moving bed reactor, and was demonstrated a higher visible-light photocatalytic activity for 2,4-dichlorophenol degradation compared with commercial P25 TiO2. When the mole ratio of TiO2 to Al2O3 equal to 1.0 showed the highest catalytic activity, the degradation percentage of 2,4-chlorophenol could be up to 92.5%, under 60 W fluorescent light irradiation for 9 hours. The high visible-light photocatalytic activity might be a synergetic effect of nitrogen doping and the form of binary metal oxide of TiO2 and gamma-Al2O3.

Oxidation of atomically thin MoS2 on SiO2

Science.gov (United States)

Yamamoto, Mahito; Cullen, William; Einstein, Theodore; Fuhrer, Michael

2013-03-01

Surface oxidation of MoS2 markedly affects its electronic, optical, and tribological properties. However, oxidative reactivity of atomically thin MoS2 has yet to be addressed. Here, we investigate oxidation of atomic layers of MoS2 using atomic force microscopy and Raman spectroscopy. MoS2 is mechanically exfoliated onto SiO2 and oxidized in Ar/O2 or Ar/O3 (ozone) at 100-450 °C. MoS2 is much more reactive to O2 than an analogous atomic membrane of graphene and monolayer MoS2 is completely etched very rapidly upon O2 treatment above 300 °C. Thicker MoS2 (> 15 nm) transforms into MoO3 after oxidation at 400 °C, which is confirmed by a Raman peak at 820 cm-1. However, few-layer MoS2 oxidized below 400 °C exhibits no MoO3 Raman mode but etch pits are formed, similar to graphene. We find atomic layers of MoS2 shows larger reactivity to O3 than to O2 and monolayer MoS2 transforms chemically upon O3 treatment even below 100 °C. Work supported by the U. of Maryland NSF-MRSEC under Grant No. DMR 05-20741.

Epitaxial Sb-doped SnO{sub 2} and Sn-doped In{sub 2}O{sub 3} transparent conducting oxide contacts on GaN-based light emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Tsai, Min-Ying [Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106 (United States); Bierwagen, Oliver, E-mail: bierwagen@pdi-berlin.de [Materials Department, University of California, Santa Barbara, CA 93106 (United States); Paul-Drude-Insitut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Speck, James S. [Materials Department, University of California, Santa Barbara, CA 93106 (United States)

2016-04-30

We demonstrate the growth of epitaxial (100)-oriented, rutile Sb-doped SnO{sub 2} (ATO) and (111)-oriented, cubic Sn-doped In{sub 2}O{sub 3} (ITO) transparent conducting oxide (TCO) contacts on top of an InGaN/GaN(0001) light emitting diode (LED) by plasma-assisted molecular beam epitaxy (PAMBE). Both oxides form rotational domains. The in-plane epitaxial alignment of the two ITO(111) rotational domains to the GaN(0001) was: GaN [21-10]|| ITO{sub Domain1}[‐ 211]|| ITO{sub Domain2}[‐ 1‐12]. A growth temperature as low as 600 °C was necessary to realize a low contact resistance between ATO and the top p-GaN layer of the LED but resulted in non-optimal resistivity (3.4 × 10{sup −} {sup 3} Ω cm) of the ATO. The current–voltage characteristics of a processed LED, however, were comparable to that of a reference LED with a standard electron-beam evaporated ITO top contact. At short wavelengths, the optical absorption of ATO was lower than that of ITO, which is beneficial even for blue LEDs. Higher PAMBE growth temperatures resulted in lower resistive ATO but higher contact resistance to the GaN, likely by the formation of an insulating Ga{sub 2}O{sub 3} interface layer. The ITO contact grown by PAMBE at 600 °C showed extremely low resistivity (10{sup −4} Ω cm) and high crystalline and morphological quality. These proof-of-principle results may lead to the development of epitaxial TCO contacts with low resistivity, well-defined interfaces to the p-GaN to help minimize contact losses, and enable further epitaxy on top of the TCO. - Highlights: • Plasma-assisted molecular beam epitaxy of SnO{sub 2}:Sb (ATO) and In{sub 2}O{sub 3}:Sn (ITO) contacts • Working light emitting diodes processed with the ATO contact on the top p-GaN layer • Low growth temperature ensures low contact resistance (limiting interface reaction). • ITO showed significantly better structural and transport properties than ATO. • ATO showed higher optical transmission at short

Indirect N2O emission due to atmospheric N deposition for the Netherlands

International Nuclear Information System (INIS)

Denier van der Gon, H.; Bleeker, A.

2005-10-01

Nitrous oxide (N2O) is a potent greenhouse gas produced in soils and aquatic systems. The UNFCCC requires participants to report 'indirect' N2O emissions, following from agricultural N losses to ground- and surface water and N deposition on (other) ecosystems due to agricultural sources. Indirect N2O emission due to atmospheric N deposition is presently not reported by the Netherlands. In this paper, we quantify the consequences of various tiers to estimate indirect N2O due to deposition for a country with a high agricultural N use and discuss the reliability and potential errors in the IPCC methodology. A literature review suggests that the current IPCC default emission factor for indirect N2O from N deposition is underestimated by a factor 2. Moreover, considering anthropogenic N emissions from agriculture only and not from e.g., traffic and industry, results in further underestimation of indirect N2O emissions. We calculated indirect N2O emissions due to Dutch anthropogenic N emissions to air by using official Dutch N emission data as input in an atmospheric transport and deposition model in combination with land use databases. Next, land use-specific emission factors were used to estimate the indirect N2O emission. This revealed that (1) for some countries, like the Netherlands, most agricultural N emitted will be deposited on agricultural soils, not on natural ecosystems and, (2) indirect N2O emissions are at least 20% higher because more specific emission factors can be applied that are higher than the IPCC default. The results suggest that indirect N2O emission due to deposition is underestimated in current N2O budgets

C, N co-doped TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} composite coatings prepared from TiC{sub 0.7}N{sub 0.3} powder using ball milling followed by oxidation

Energy Technology Data Exchange (ETDEWEB)

Hao, Liang, E-mail: haoliang@tust.edu.cn [Tianjin Key Lab of Integrated Design and On-line Monitoring for Light Industry & Food Machinery and Equipment, Tianjin (China); College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Wang, Zhenwei, E-mail: 1004329228@qq.com [School of Naval Architecture and Ocean Engineering, Harbin Institute of Technology, Weihai, No. 2, Wenhua West Road, Weihai 264209 (China); Zheng, Yaoqing, E-mail: 13612177268@163.com [College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Li, Qianqian, E-mail: 1482471595@qq.com [College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Guan, Sujun, E-mail: sujunguan1221@gmail.com [College of Mechanical Engineering & Graduate School, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Zhao, Qian, E-mail: zhaoqian@tust.edu.cn [Tianjin Key Lab of Integrated Design and On-line Monitoring for Light Industry & Food Machinery and Equipment, Tianjin (China); College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Cheng, Lijun, E-mail: chenglijun@tust.edu.cn [Tianjin Key Lab of Integrated Design and On-line Monitoring for Light Industry & Food Machinery and Equipment, Tianjin (China); College of Mechanical Engineering, Tianjin University of Science & Technology, No. 1038 Dagu Nanlu, Hexi District, Tianjin 300222 (China); Lu, Yun, E-mail: luyun@faculty.chiba-u.jp [College of Mechanical Engineering & Graduate School, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Liu, Jizi, E-mail: jzliu@njust.edu.cn [Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, No. 200, Xiaolingwei Street, Nanjing 210094 (China)

2017-01-01

Highlights: • TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} coatings were prepared by ball milling followed by oxidation. • In situ co-doping of C and N with simultaneous TiO{sub 2} formation was observed. • Improved photocatalytic activity under UV/visible light was noticed. • Synergism in co-doping and heterojunction formation promoted carrier separation. - Abstract: Ball milling followed by heat oxidation was used to prepared C, N co-doped TiO{sub 2} coatings on the surfaces of Al{sub 2}O{sub 3} balls from TiC{sub 0.7}N{sub 0.3} powder. The as-prepared coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectrophotometer (UV–vis). The results show that continuous TiC{sub 0.7}N{sub 0.3} coatings were formed after ball milling. C, N co-doped TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} composite coatings were prepared after the direct oxidization of TiC{sub 0.7}N{sub 0.3} coatings in the atmosphere. However, TiO{sub 2} was hardly formed in the surface layer of TiC{sub 0.7}N{sub 0.3} coatings within a depth less than 10 nm during the heat oxidation of TiC{sub 0.7}N{sub 0.3} coatings in carbon powder. Meanwhile, the photocatalytic activity evaluation of these coatings was conducted under the irradiation of UV and visible light. All the coatings showed photocatalytic activity in the degradation of MB no matter under the irradiation of UV or visible light. The C, N co-doped TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} composite coatings showed the most excellent performance. The enhancement under visible light irradiation should attribute to the co-doping of carbon and nitrogen, which enhances the absorption of visible light. The improvement of photocatalytic activity under UV irradiation should attribute to the synergistic effect of C, N co-doping, the formation of rutile-anatase mixed phases and the TiO{sub 2}/TiC{sub 0.7}N{sub 0.3} composite microstructure.

Comparison and mechanism of photocatalytic activities of N-ZnO and N-ZrO2 for the degradation of rhodamine 6G.

Science.gov (United States)

Sudrajat, Hanggara; Babel, Sandhya

2016-05-01

N-doped ZnO (N-ZnO) and N-doped ZrO2 (N-ZrO2) are synthesized by novel, simple thermal decomposition methods. The catalysts are evaluated for the degradation of rhodamine 6G (R6G) under visible and UV light. N-ZnO exhibits higher dye degradation under both visible and UV light compared to N-ZrO2 due to possessing higher specific surface area, lower crystalline size, and lower band gap. However, it is less reusable than N-ZrO2 and its photocatalytic activity is also deteriorated at low pH. At the same intensity of 3.5 W/m(2), UVC light is shown to be a better UV source for N-ZnO, while UVA light is more suitable for N-ZrO2. At pH 7 with initial dye concentration of 10 mg/L, catalyst concentration of 1 g/L, and UVC light, 94.3 % of R6G is degraded by N-ZnO within 2 h. Using UVA light under identical experimental conditions, 93.5 % degradation of R6G is obtained by N-ZrO2. Moreover, the type of light source is found to determine the reactive species produced in the R6G degradation by N-ZnO and N-ZrO2. Less oxidative reactive species such as superoxide radical and singlet oxygen play a major role in the degradation of R6G under visible light. On the contrary, highly oxidative hydroxyl radicals are predominant under UVC light. Based on the kinetic study, the adsorption of R6G on the catalyst surface is found to be the controlling step.

High-throughput identification of higher-κ dielectrics from an amorphous N2-doped HfO2–TiO2 library

International Nuclear Information System (INIS)

Chang, K.-S.; Lu, W.-C.; Wu, C.-Y.; Feng, H.-C.

2014-01-01

Highlights: • Amorphous N 2 -doped HfO 2 –TiO 2 libraries were fabricated using sputtering. • Structure and quality of the dielectric and interfacial layers were investigated. • κ (54), J L < 10 −6 A/cm 2 , and equivalent oxide thickness (1 nm) were identified. - Abstract: High-throughput sputtering was used to fabricate high-quality, amorphous, thin HfO 2 –TiO 2 and N 2 -doped HfO 2 –TiO 2 (HfON–TiON) gate dielectric libraries. Electron probe energy dispersive spectroscopy was used to investigate the structures, compositions, and qualities of the dielectric and interfacial layers of these libraries to determine their electrical properties. A κ value of approximately 54, a leakage current density <10 −6 A/cm 2 , and an equivalent oxide thickness of approximately 1 nm were identified in an HfON–TiON library within a composition range of 68–80 at.% Ti. This library exhibits promise for application in highly advanced metal–oxide–semiconductor (higher-κ) gate stacks

High temperature oxidation behaviour of nanostructured cermet coatings in a mixed CO2 - O2 environment

Science.gov (United States)

Farrokhzad, M. A.; Khan, T. I.

2014-06-01

Nanostructured ceramic-metallic (cermet) coatings composed of nanosized ceramic particles (α-Al2O3 and TiO2) dispersed in a nickel matrix were co-electrodeposited and then oxidized at 500°C, 600°C and 700°C in a mixed gas using a Thermo-gravimetric Analysis (TGA) apparatus. The mixed gas was composed of 15% CO2, 10% O2 and 75% N2. This research investigates the effects of CO2 and O2 partial pressures on time-depended oxidation rates for coatings and compared them to the results from atmospheric oxidation under similar temperatures. The increase in partial pressure of oxygen due to the presence of CO2 at each tested temperature was calculated and correlated to the oxidation rate of the coatings. The results showed that the presence of CO2 in the system increased the oxidation rate of cermet coatings when compared to atmospheric oxidation at the same temperature. It was also shown that the increase in the oxidation rate is not the result of CO2 acting as the primary oxidant but as a secondary oxidant which results in an increase of the total partial pressure of oxygen and consequently higher oxidation rates. The WDS and XRD analyses results showed that the presence of nanosized TiO2 particles in a nickel matrix can improve oxidation behaviour of the coatings by formation of Ni-Ti compounds on oxidizing surface of the coating which was found beneficiary in reducing the oxidation rates for cermet coatings.

Ab initio studies of O-2(-) (H2O)(n) and O-3(-) (H2O)(n) anionic molecular clusters, n

DEFF Research Database (Denmark)

Bork, Nicolai Christian; Kurten, T.; Enghoff, Martin Andreas Bødker

2011-01-01

that anionic O-2(-)(H2O)n and O-3(-)(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding....... Although clustering up to 12 H2O, we find that the O-2 and O-3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O-2(-) and O-3(-) speicies are thus accessible for further reactions. We consider the distributions of cluster sizes as function of altitude before...

European-scale modelling of groundwater denitrification and associated N2O production

International Nuclear Information System (INIS)

Keuskamp, J.A.; Drecht, G. van; Bouwman, A.F.

2012-01-01

This paper presents a spatially explicit model for simulating the fate of nitrogen (N) in soil and groundwater and nitrous oxide (N 2 O) production in groundwater with a 1 km resolution at the European scale. The results show large heterogeneity of nitrate outflow from groundwater to surface water and production of N 2 O. This heterogeneity is the result of variability in agricultural and hydrological systems. Large parts of Europe have no groundwater aquifers and short travel times from soil to surface water. In these regions no groundwater denitrification and N 2 O production is expected. Predicted N leaching (16% of the N inputs) and N 2 O emissions (0.014% of N leaching) are much less than the IPCC default leaching rate and combined emission factor for groundwater and riparian zones, respectively. - Highlights: ► Groundwater denitrification and N 2 O production was modelled at the European scale. ► In large parts of Europe no groundwater denitrification is expected. ► N leaching and N 2 O emission in Europe are much less than the IPCC default values. - European groundwater denitrification is spatially variable, and associated nitrous oxide production is much less than based on the IPCC default estimate.

Rate law of Fe(II) oxidation under low O2 conditions

Science.gov (United States)

Kanzaki, Yoshiki; Murakami, Takashi

2013-12-01

Despite intensive studies on Fe(II) oxidation kinetics, the oxidation rate law has not been established under low O2 conditions. The importance of Fe(II) oxidation under low O2 conditions has been recently recognized; for instance, the Fe(II)/Fe(III) compositions of paleosols, ancient soils formed by weathering, can produce a quantitative pattern of the atmospheric oxygen increase during the Paleoproterozoic. The effects of partial pressure of atmospheric oxygen (PO2) on the Fe(II) oxidation rate were investigated to establish the Fe(II) oxidation rate - PO2 relationships under low O2 conditions. All oxidation experiments were carried out in a glove box by introducing Ar gas at ∼10-5-∼10-4 atm of PO2, pH 7.57-8.09 and 22 °C. Luminol chemiluminescence was adopted to measure low Fe(II) concentrations (down to ∼2 nM). Combining previous data under higher PO2 conditions (10-3-0.2 atm) with the present data, the rate law for Fe(II) oxidation over a wide range of PO2 (10-5-0.2 atm) was found to be written as: d[Fe(II)]/dt=-k[Fe(II)][[]2 where the exponent of [O2], x, and the rate constant, k, change from x = 0.98 (±0.04) and log k = 15.46 (±0.06) at ∼6 × 10-3-0.2 atm of PO2 to x = 0.58 (±0.02) and log k = 13.41 (±0.03) at 10-5-∼6 × 10-3 atm of PO2. The most plausible mechanism that explains the change in x under low O2 conditions is that, instead of O2, oxygen-derived oxidants, H2O2 and to some extent, O2rad -, dominate the oxidation reactions at PO2. The rate law found in the present study requires us to reconsider distributions of Fe redox species at low PO2 in natural environments, especially in paleoweathering profiles, and may provide a deeper understanding of the evolution of atmospheric oxygen in the Precambrian.

Synthesis and physico-chemical characterization of CeO2/ZrO2-SO42- mixed oxides

International Nuclear Information System (INIS)

Hernandez E, J. M.; Silva R, R.; Garcia A, R.; Garcia S, L. A.; Handy, B. E.; Cardenas G, G.; Cueto H, A.

2012-01-01

Environmentally friendly solid-acid catalysts CeO 2 /ZrO 2 -SO 4 2- were prepared by the sol gel method varying CeO 2 content (10, 20 and 30 wt %) and using sulfation in situ, maintaining the sulfate ions amount present in the materials at 20 wt %. ZrO 2 and ZrO 2 -SO 4 2- were also prepared for comparison proposes using the same synthesis method. The materials were characterized by X-ray diffraction, nitrogen physisorption, potentiometric titration with n-butylamine, decomposition of 2-propanol and n-pentane isomerization. The specific surface area of ZrO 2 -SO 4 2- was high (160 m 2 /g) compared with the unmodified ZrO 2 (80 m 2 /g), however this area decreased with increasing the CeO 2 content (37-100 m 2 /g). There was no significant effect of CeO 2 on the tetragonal structure of ZrO 2 -SO 4 2- . The variation of acid sites amount runs parallel to the change of specific surface area. The acid sites amount decreased with increasing cerium oxide content. The decomposition of 2-propanol results fundamentally in the formation of dehydration products such as propylene and diisopropyl ether, both involving acid sites. In addition, a good performance during the n-pentane isomerization was observed for these materials. The selectivity towards isopentane reaches 84% when the Pt/CeO 2 /ZrO 2 -SO 4 2- catalyst with the highest CeO 2 content was used. (Author)

Catalytic oxidation of n-hexane promoted by Ce1−xCuxO2 catalysts prepared by one-step polymeric precursor method

International Nuclear Information System (INIS)

Araújo, Vinícius D.; Lima, Maurício M. de; Cantarero, Andrés; Bernardi, Maria I.B.; Bellido, Jorge D.A.; Assaf, Elisabete M.; Balzer, Rosana; Probst, Luiz F.D.; Fajardo, Humberto V.

2013-01-01

Ceria-supported copper catalysts (Ce 1−x Cu x O 2 , with x (mol) = 0, 0.01, 0.03, 0.05 and 0.10) were prepared in one step through the polymeric precursor method. The textural properties of the catalysts were investigated by X-ray diffraction (XRD), Rietveld refinement, N 2 -physisorption (BET surface area), electron paramagnetic resonance (EPR), UV–visible diffuse reflectance and photoluminescence spectroscopies and temperature-programmed reduction (TPR). In a previous study ceria-supported copper catalysts were found to be efficient in the preferential oxidation of CO. In this study, we extended the catalytic application of Ce 1−x Cu x O 2 systems to n-hexane oxidation and it was verified that the catalysts were highly efficient in the proposed reaction. The best performance (up to 95% conversion) was observed for the catalysts with low copper loads (Ce 0.97 Cu 0.03 O 2 and Ce 0.99 Cu 0.01 O 2 , respectively). The physicochemical characterizations revealed that these behaviors could be attributed to the copper species present in the catalysts and the interaction between CuO and CeO 2 , which vary according to the copper content. - Highlights: • Synthesis of CuO/CeO2 catalysts by the one-step polymeric precursor method. • 95% n-hexane conversion on Ce0.97Cu0.03O2 catalyst. • Redox properties play a key role in the catalytic performance

Reduced graphene oxide/CeO{sub 2} nanocomposite with enhanced photocatalytic performance

Energy Technology Data Exchange (ETDEWEB)

Kaur, Jasmeet, E-mail: jasmeet.dayal@gmail.com; Anand, Kanika; Singh, Gurpreet; Hastir, Anita; Virpal,; Singh, Ravi Chand [Laboratory For Sensors and Physics Education, Department of Physics, GND University, Amritsar-143005 (India); Anand, Kanica [Semiconductors Laboratory, Department of Physics, GND University, Amritsar– 143005 (India)

2015-05-15

In this work, reduced graphene oxide /cerium oxide (RGO/CeO{sub 2}) nanocomposite was synthesized by in situ reduction of cerium nitrate Ce(NO{sub 3}){sub 3}·6H{sub 2}O in the presence of graphene oxide by hydrazine hydrate (N{sub 2}H{sub 4}.H{sub 2}O). The intrinsic characteristics of as-prepared nanocomposite were studied using powder x-ray diffraction (XRD), Raman spectroscopy and field-emission scanning electron microscopy (FESEM). The photocatalytic degradation of methylene blue (MB) was employed as a model reaction to evaluate the photocatalytic activity of the RGO/CeO{sub 2} nanocomposite. The as-obtained RGO/CeO{sub 2} nanocomposite displays a significantly enhanced photocatalytic degradation of MB dye in comparison with bare CeO{sub 2} nanoparticles under sunlight irradiation, which can be attributed to the improved separation of electron-hole pairs and enhanced adsorption performance due to presence of RGO.

Isotopologue fractionation during N(2)O production by fungal denitrification.

Science.gov (United States)

Sutka, Robin L; Adams, Gerard C; Ostrom, Nathaniel E; Ostrom, Peggy H

2008-12-01

Identifying the importance of fungi to nitrous oxide (N2O) production requires a non-intrusive method for differentiating between fungal and bacterial N2O production such as natural abundance stable isotopes. We compare the isotopologue composition of N2O produced during nitrite reduction by the fungal denitrifiers Fusarium oxysporum and Cylindrocarpon tonkinense with published data for N2O production during bacterial nitrification and denitrification. The fractionation factors for bulk nitrogen isotope values for fungal denitrification were in the range -74.7 to -6.6 per thousand. There was an inverse relationship between the absolute value of the fractionation factors and the reaction rate constant. We interpret this in terms of variation in the relative importance of the rate constants for diffusion and enzymatic reduction in controlling the net isotope effect for N2O production during fungal denitrification. Over the course of nitrite reduction, the delta(18)O values for N2O remained constant and did not exhibit a relationship with the concentration characteristic of an isotope effect. This probably reflects isotopic exchange with water. Similar to the delta(18)O data, the site preference (SP; the difference in delta(15)N between the central and outer N atoms in N2O) was unrelated to concentration during nitrite reduction and, therefore, has the potential to act as a conservative tracer of production from fungal denitrification. The SP values of N2O produced by F. oxysporum and C. tonkinense were 37.1 +/- 2.5 per thousand and 36.9 +/- 2.8 per thousand, respectively. These SP values are similar to those obtained in pure culture studies of bacterial nitrification but quite distinct from SP values for bacterial denitrification. The large magnitude of the bulk nitrogen isotope fractionation and the delta(18)O values associated with fungal denitrification are distinct from bacterial production pathways; thus multiple isotopologue data holds much promise for

A novel fuzzy-logic control strategy minimizing N2O emissions

DEFF Research Database (Denmark)

Boiocchi, Riccardo; Gernaey, Krist; Sin, Gürkan

2017-01-01

is useful for those plants having AOB denitrification as the main N2O producing process. However, in treatment plants having incomplete NH2OH oxidation as the main N2O producing pathway, a cascade controller configuration adapting the oxygen supply to respect only the effluent ammonium concentration limits...

Dynamics of N₂O production pathways analyzed by ¹⁵N¹⁸O isotope labeling

DEFF Research Database (Denmark)

Jensen, Marlene Mark; Ma, Chun; Lavik, Gaute

Nitrous oxide production associated with biological nitrogen transformations can contribute substantially to the CO2 footprint of both man-made and natural systems, but the pathways and regulation of N2O production are poorly understood. We developed a 15N/18O dual isotope labelling technique...

Preparation of Ginsenoside Rg3 and Protection against H2O2-Induced Oxidative Stress in Human Neuroblastoma SK-N-SH Cells

Directory of Open Access Journals (Sweden)

Gang Li

2014-01-01

Full Text Available The aim of this study is to evaluate the protection of ginsenoside Rg3 against oxidative stress in human neuroblastoma SK-N-SH cells. 20(R-ginsenoside Rg3 (20(R-Rg3 and 20(S-ginsenoside Rg3 (20(S-Rg3 were prepared by the method of chemical degradation and column chromatography, and the structure of the two compounds was characterized by 1H-NMR and 13C-NMR spectroscopy. MTT assay and LDH leakage assay were used to determine the cell viability and the oxidative stress cellular model was established by means of H2O2 (600 μM for 4 h. We also investigated the changes of intracellular MDA content, SOD activity, and ROS formation after the treatment of ginsenoside Rg3 for 20 h. The results indicated that both 20 (R-Rg3 and 20 (S-Rg3 had obvious protection against H2O2-induced oxidative stress in SK-N-SH cells. Moreover, 20(R-Rg3 exhibited better antioxidant activity than 20(S-Rg3 in vitro. These findings are expected to provide some implication for further research and application of ginsenoside Rg3 in neuroprotection.

Amide-N-oxide heterosynthon and amide dimer homosynthon in cocrystals of carboxamide drugs and pyridine N-oxides.

Science.gov (United States)

Babu, N Jagadeesh; Reddy, L Sreenivas; Nangia, Ashwini

2007-01-01

The carboxamide-pyridine N-oxide heterosynthon is sustained by syn(amide)N-H...O-(oxide) hydrogen bond and auxiliary (N-oxide)C-H...O(amide) interaction (Reddy, L. S.; Babu, N. J.; Nangia, A. Chem. Commun. 2006, 1369). We evaluate the scope and utility of this heterosynthon in amide-containing molecules and drugs (active pharmaceutical ingredients, APIs) with pyridine N-oxide cocrystal former molecules (CCFs). Out of 10 cocrystals in this study and 7 complexes from previous work, amide-N-oxide heterosynthon is present in 12 structures and amide dimer homosynthon occurs in 5 structures. The amide dimer is favored over amide-N-oxide synthon in cocrystals when there is competition from another H-bonding functional group, e.g., 4-hydroxybenzamide, or because of steric factors, as in carbamazepine API. The molecular organization in carbamazepine.quinoxaline N,N'-dioxide 1:1 cocrystal structure is directed by amide homodimer and anti(amide)N-H...O-(oxide) hydrogen bond. Its X-ray crystal structure matches with the third lowest energy frame calculated in Polymorph Predictor (Cerius(2), COMPASS force field). Apart from generating new and diverse supramolecular structures, hydration is controlled in one substance. 4-Picoline N-oxide deliquesces within a day, but its cocrystal with barbital does not absorb moisture at 50% RH and 30 degrees C up to four weeks. Amide-N-oxide heterosynthon has potential utility in both amide and N-oxide type drug molecules with complementary CCFs. Its occurrence probability in the Cambridge Structural Database is 87% among 27 structures without competing acceptors and 78% in 41 structures containing OH, NH, H(2)O functional groups.

Oxidation and photo-oxidation of water on TiO2 surface

DEFF Research Database (Denmark)

Valdes, A.; Qu, Z.W.; Kroes, G.J.

2008-01-01

The oxidation and photo-oxidation of water on the rutile TiO2(110) surface is investigated using density functional theory (DFT) calculations. We investigate the relative stability of different surface terminations of TiO2 interacting with H2O and analyze the overpotential needed for the electrol...

Distinguishing sources of N2O in European grasslands by stable isotope analysis

NARCIS (Netherlands)

Wrage, N.; Lauf, J.; Prado, del A.; Pinto, M.; Pietrzak, S.; Yamulki, S.; Oenema, O.; Gebauer, G.

2004-01-01

Nitrifiers and denitrifiers are the main producers of the greenhouse gas nitrous oxide (N2O). Knowledge of the respective contributions of each of these microbial groups to N2O production is a prerequisite for the development of effective mitigation strategies for N2O. Often, the differentiation is

Activity and deactivation of sulphated TiO2- and ZrO2-based V, Cu, and Fe oxide catalysts for NO abatement in alkali containing flue gases

DEFF Research Database (Denmark)

Kustov, Arkadii; Rasmussen, Søren Birk; Fehrmann, Rasmus

2007-01-01

Vanadia, copper and iron oxide catalysts supported on conventional TiO2, ZrO2, and sulphated-TiO2 and ZrO2 have been prepared. These catalysts were characterized by elemental analysis, N-2-BET, XRD, and NH3-TPD methods. The influence of potassium oxide additives on the acidity and activity...... of the catalysts with potassium leads to a considerable decrease of their catalytic activity. In the case of the traditional carriers (TiO2, ZrO2), the poisoning of the catalyst with small amounts of potassium oxide (K/metal ratio...

When the Sun's Away, N2O5 Comes Out to Play: An Updated Analysis of Ambient N2O5 Heterogeneous Chemistry

Science.gov (United States)

McDuffie, E. E.; Brown, S. S.

2017-12-01

The heterogeneous chemistry of N2O5 impacts the budget of tropospheric oxidants, which directly controls air quality at Earth's surface. The reaction between gas-phase N2O5 and aerosol particles occurs largely at night, and is therefore more important during the less-intensively-studied winter season. Though N2O5-aerosol interactions are vital for the accurate understanding and simulation of tropospheric chemistry and air quality, many uncertainties persist in our understanding of how various environmental factors influence the reaction rate and probability. Quantitative and accurate evaluation of these factors directly improves the predictive capabilities of atmospheric models, used to inform mitigation strategies for wintertime air pollution. In an update to last year's presentation, The Wintertime Fate of N2O5: Observations and Box Model Analysis for the 2015 WINTER Aircraft Campaign, this presentation will focus on recent field results regarding new information about N2O5 heterogeneous chemistry and future research directions.

Oxidation Reactivity Channels for 2-(Pyridin-2-yl)-N,N-diphenyl-acetamides

Energy Technology Data Exchange (ETDEWEB)

Pailloux, Sylvie [University of New Mexico, Albuquerque; Binyamin, Iris [University of New Mexico, Albuquerque; Kim, Sung-jun [University of New Mexico, Albuquerque; Deck, Lorraine M. [University of New Mexico, Albuquerque; Rapko, Brian M. [Pacific Northwest National Laboratory (PNNL); Hay, Benjamin [ORNL; Duesler, Eileen N. [University of New Mexico, Albuquerque; Paine, Robert T. [University of New Mexico, Albuquerque

2007-11-01

Synthetic routes to 2-(pyridin-2-yl)-N,N-diphenylacetamide and 2-(6-methylpyridin-2-yl)-N,N-diphenyl-acetamide are described along with results from the chemical oxidation of these compounds with peracetic acid, m-chloroperbenzoic acid, and OXONE. In each case, oxidations generate four products in varying amounts depending on the oxidant and reaction conditions. Each product has been characterized by spectroscopic methods and the molecular structures of several of the new compounds have been confirmed by X-ray crystallography.

CuO reduction induced formation of CuO/Cu2O hybrid oxides

Science.gov (United States)

Yuan, Lu; Yin, Qiyue; Wang, Yiqian; Zhou, Guangwen

2013-12-01

Reduction of CuO nanowires results in the formation of a unique hierarchical hybrid nanostructure, in which the parent oxide phase (CuO) works as the skeleton while the lower oxide (Cu2O) resulting from the reduction reaction forms as partially embedded nanoparticles that decorate the skeleton of the parent oxide. Using in situ transmission electron microscopy observations of the reduction process of CuO nanowires, we demonstrate that the formation of such a hierarchical hybrid oxide structure is induced by topotactic nucleation and growth of Cu2O islands on the parent CuO nanowires.

Effects of Carbon and Cover Crop Residues on N2O and N2 Emissions

Science.gov (United States)

Burger, M.; Cooperman, Y.; Horwath, W. R.

2016-12-01

In Mediterranean climate, nitrous oxide emissions occurring with the first rainfall after the dry summer season can contribute up to 50% of agricultural systems' total annual emissions, but the drivers of these emissions have not been clearly identified, and there are only few measurements of atmospheric nitrogen (N2) production (denitrification) during these events. In lab incubations, we investigated N2O and N2 production, gross ammonification and nitrification, and microbial N immobilization with wet-up in soil from a vineyard that was previously fallow or where cover crop residue had been incorporated the previous spring. Before the first rainfall, we measured 120 mg dissolved organic carbon (DOC-C) kg-1 soil in the 0-5 cm layer of this vineyard, and after the rain 10 mg DOC-C kg-1, while nitrate levels before the rain were cover cropped soil. The N2O/N2 production was 2, 7, 9, and 86% in fallow, legume-grass mixture, rye, and legume cover cropped soil. The N2O/N2 ratio tended to increase with lower DOC (post-rain) levels in the soil. The results suggest that accumulated carbon in dry surface soil is the main driving factor of N2O and N2 emissions through denitrification with the first rainfall after prolonged dry periods.

Efficient oxidative dissolution of V2O3 by the in situ electro-generated reactive oxygen species on N-doped carbon felt electrodes

International Nuclear Information System (INIS)

Xue, Yudong; Wang, Yunting; Zheng, Shili; Sun, Zhi; Zhang, Yi; Jin, Wei

2017-01-01

Highlights: • Novel alkaline electro-Fenton-like was applied for V 2 O 3 oxidative dissolution. • N-doped carbon felt electrode was fabricated for the two-electron ORR. • ROS including ·OH and HO 2 − was in-situ generated from the electrochemical system. • A significant enhancement of V 2 O 3 dissolution was achieved due to the ROS. - Abstract: Oxidative dissolution is a critical step for the efficient remediation of heavy metal oxides in large-scale solid wastes. In the present study, a novel electro-oxidative dissolution process of V 2 O 3 to VO 4 3− is achieved by the in-situ generated reactive oxygen species on the N-doped carbon felt cathode in alkaline media. The electro-catalytic HO 2 − generation and hydrophilic behavior were significantly enhanced by the introduction of nitrogen-containing functional groups. Besides, the mechanism of electrochemical vanadium conversion is systematically illustrated, and a vanadium self-induced electro-Fenton-like reaction is proposed. By employing the radical quenching and ESR measurements, the contributions for V(III) dissolution is determined to be 43.5% by HO 2 − and 56.5% by hydroxyl radicals, respectively. It should be noted that the V 2 O 3 solid particles can be efficiently dissolved via adsorption-reaction scheme on the carbon felt electrode. This novel electrochemical strategy provides a promising solution for the heavy metal oxide treatment and further understanding for the in situ reactive oxygen species.

Effect of Preparation Method on Catalytic Properties of Co-Mn-Al Mixed Oxides for N2O Decomposition.

Czech Academy of Sciences Publication Activity Database

Klyushina, A.; Pacultová, K.; Karásková, K.; Jirátová, Květa; Ritz, M.; Fridrichová, D.; Volodorskaja, A.; Obalová, L.

2016-01-01

Roč. 425, DEC 15 (2016), s. 237-247 ISSN 1381-1169 R&D Projects: GA ČR GA14-13750S Institutional support: RVO:67985858 Keywords : Co-Mn-Al mixed oxide * N2O decomposition * preparation methods Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 4.211, year: 2016

Photocatalytic decomposition of N{sub 2}O over TiO{sub 2}/g-C{sub 3}N{sub 4} photocatalysts heterojunction

Energy Technology Data Exchange (ETDEWEB)

Kočí, K., E-mail: kamila.koci@vsb.cz [Institute of Environmental technologies, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic); Reli, M.; Troppová, I.; Šihor, M. [Institute of Environmental technologies, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic); Kupková, J. [Nanotechnology center, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic); Kustrowski, P. [Faculty of Chemistry, Jagiellonian University in Kraków, ul. Ingardena 3, 30-060 Kraków (Poland); Praus, P. [Institute of Environmental technologies, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic); Department of Chemistry, VŠB Technical University of Ostrava 17. listopadu 15/2172, 708 00 Ostrava (Czech Republic)

2017-02-28

Highlights: • TiO{sub 2}/g-C{sub 3}N{sub 4} photocatalysts with the various TiO{sub 2}/g-C{sub 3}N{sub 4} weight ratios. • N{sub 2}O photocatalytic decomposition under UVC and UVA irradiation. • Heterojunction on the TiO{sub 2}/g-C{sub 3}N{sub 4} interface play an important role. • Optimal ratio of TiO{sub 2}:g-C{sub 3}N{sub 4} was 1:2 for the highest activity at UVA irradiation. - Abstract: TiO{sub 2}/g-C{sub 3}N{sub 4} photocatalysts with the various TiO{sub 2}/g-C{sub 3}N{sub 4} weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO{sub 2} was prepared by thermal hydrolysis and pure g-C{sub 3}N{sub 4} was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV–vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO{sub 2} and g-C{sub 3}N{sub 4} were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO{sub 2}/g-C{sub 3}N{sub 4} nanocomposites showed moderate improvement compared to pure g-C{sub 3}N{sub 4} but pure TiO{sub 2} proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO{sub 2}/g-C{sub 3}N{sub 4} (1:2) nanocomposite exhibited an increase compared to pure TiO{sub 2}. Nevertheless, further increase of g-C{sub 3}N{sub 4} amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO{sub 2} and g-C{sub 3}N{sub 4} have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C{sub 3}N{sub 4}. This is

Total Ionizing Dose Effects of Si Vertical Diffused MOSFET with SiO2 and Si3N4/SiO2 Gate Dielectrics

Directory of Open Access Journals (Sweden)

Jiongjiong Mo

2017-01-01

Full Text Available The total ionizing dose irradiation effects are investigated in Si vertical diffused MOSFETs (VDMOSs with different gate dielectrics including single SiO2 layer and double Si3N4/SiO2 layer. Radiation-induced holes trapping is greater for single SiO2 layer than for double Si3N4/SiO2 layer. Dielectric oxidation temperature dependent TID effects are also studied. Holes trapping induced negative threshold voltage shift is smaller for SiO2 at lower oxidation temperature. Gate bias during irradiation leads to different VTH shift for different gate dielectrics. Single SiO2 layer shows the worst negative VTH at VG=0 V, while double Si3N4/SiO2 shows negative VTH shift at VG=-5 V, positive VTH shift at VG=10 V, and negligible VTH shift at VG=0 V.