Low N2 Research Articles

Mechanisms of element precipitation in carbonatite-related rare-earth element deposits: Evidence from fluid inclusions in the Maoniuping deposit, Sichuan Province, southwestern China

Carbonatite-related rare-earth element (REE) deposits (CARDs) are the major global source of REEs. The ore-forming fluids of CARDs usually comprise multiple components and record complicated evolutions. The Maoniuping REE deposit, located in the eastern Tibetan Plateau, is the second-largest CARD in China and contains total reserves of 3.17 Mt of light rare-earth oxides (REOs). Geochronological and geological data show that the deposit was formed at ∼25 Ma and was only moderately affected by tectonic and hydrothermal activities, thereby allowing us to study the evolution of ore fluids as well as the mechanisms of REE mineralization. The Maoniuping REE deposit is spatially associated with a carbonatite–syenite complex and includes two sections: Guangtoushan and Dagudao. The Dagudao section is the main focus of exploration and hosts well-developed vein systems. In the uppermost vein system, minerals are zoned from the syenite wall-rock contact to the vein centers in the order of biotite, aegirine-augite, arfvedsonite, calcite, quartz, barite, fluorite, and bastnäsite-(Ce). Based on geological observations and the petrography of fluid inclusions, the mineralization processes are classified into magmatic, pegmatitic, hydrothermal I, hydrothermal II, and REE stages. The inclusions in these stages include melt (M), melt–fluid (M–L), pure CO2 (C), aqueous–CO2 (L–C), aqueous–CO2 with crystals (L − C + S), liquid–vapor aqueous with crystals (L − V + S), and liquid–vapor (L–V) type inclusions. The magmatic stage is marked by a carbonatite–syenite complex with minor bastnäsite-(Ce), whereas the pegmatitic stage consists of coarse-grained calcite, barite, fluorite, and quartz that contain M, M–L, and L–C type inclusions with a fluid system of NaCl–Na2SO4–H2O–CO2 at high temperature (>600 °C) and high salinity (>45 wt% NaCl equiv.). The hydrothermal I stage is characterized by fenitization and is marked by aegirine-augite and arfvedsonite containing abundant L–V and few L–C type inclusions. This stage is characterized by high temperatures (∼480 °C) and moderate salinity (10.2–17.9 wt% NaCl equiv.), with a fluid system of NaCl–Na2SO4–H2O and minor CO2 and CH4 + C2H6. The hydrothermal II stage is dominated by L–C, L − C + S, L − V + S, and L–V type inclusions that are hosted in barite, calcite, fluorite, and quartz, and formed at moderate to high temperatures (260–350 °C), with a wide range of salinity (9.4–47.8 wt% NaCl equiv.), a fluid system of NaCl–Na2SO4–CO2–H2O, and abundant CH4 + C2H6. During the REE stage, pervasive bastnäsite-(Ce) containing abundant L–V type and few L–C type inclusions crystallized under low temperatures (160–240 °C) and low salinities (8.8–13.1 wt% NaCl equiv.) with a fluid system of NaCl–H2O and minor CO2 and CH4 + C2H6.The results of ion-chromatographic analysis show that the ore fluids are rich in Na+, K+, Cl−, F−, and (SO4)2−, and have low Cl−/(SO4)2− ratios (0.78–2.00), showing a marked contrast with the fluids of granite-related REE deposits (Cl−/(SO4)2− > 50) and a similarity to subcontinental lithospheric mantle (SCLM). The δD and δ18Ofluid values and the high N2/Ar ratios indicate that the ore fluids originated from carbonatitic magma and were dominated by magmatic water during the hydrothermal I stage, whereas magmatic and meteoric water co-existed during the hydrothermal II and REE stages. Moreover, the higher ratios of CO2/N2 (9–64) and CO2/CH4 (17–472) and the higher concentrations of CO2, CH4, C2H6, and N2 in the hydrothermal II stage compared with the hydrothermal I stage are attributed to intense immiscibility that resulted from decompression and is constrained to temperatures of 310–350 °C and pressures of 2.0–2.4 kbar. In contrast, microthermometric data and low CH4, C2H6, and N2 contents for the REE stage show that fluid cooling and mixing with meteoric water played an important role during the intensive mineralization of this stage, which occurred under shallow open-system conditions at temperatures of ∼200 °C and pressures of <0.5 kbar. The mineral assemblages, together with experimental petrology results, suggest that the REE transport capability of the hydrothermal fluids was due to the high contents of (SO4)2−, Cl−, and F− complexes. In addition, CO2 that separates during immiscibility is known to act as a buffer that constrains the pH of ore fluids. Thus, immiscibility during the hydrothermal II stage could have provided favorable conditions for the migration of REEs. The subsequent cooling of fluids, the involvement of meteoric water, and increased fluid pH, favored the precipitation of REEs in the Maoniuping deposit.

Effect of aeration and hydraulic loading rate on nitrogen removal by subsurface infiltration systems.

This study investigated the effect of hydraulic loading rate (HLR) on matrix dissolved oxygen (DO), organic matter removal, nitrogen removal, N2 O emissions, and the abundances of functional genes participating in nitrogen removal in intermittent aerated mode (IAM) and nonaerated mode (NAM) subsurface infiltration systems (SISs). In contrast to NAM SISs, IAM SISs were able to create aerobic conditions in the upper matrix (above 50cm depth) and anoxic or anaerobic conditions in the lower matrix (below 80cm depth). Subsequently, this enhanced the abundance of functional genes related to nitrogen removal. Chemical oxygen demand (COD) and nitrogen removal performance were significantly higher under IAM SISs than with NAM SISs. Under a HLR of 0.3m3 /(m2 d), the IAM SIS was able to achieve low N2 O emissions (12.6mg/[m2 d]) along with removal efficiencies of 90.5%, 91.4%, and 85.7% for COD, ammonia nitrogen ( -N), and total nitrogen (TN), respectively. PRACTITIONER POINTS: Intermittent aeration successfully realized sequential aerobic and anaerobic conditions at 50 cm depth and at 80 and 110 cm depths of a subsurface infiltration system. Intermittent aeration reduced N2 O emissions and improved hydraulic loading rate and organic matter, nitrogen removal efficiencies. Intermittent aeration enhanced the abundances of amoA, nxrA, napA, narG, nirS, nirK, qnorB, and nosZ.

Syntheses, structures and immobilization of arene-ruthenium complexes bearing phosphine ligands with methoxysilyl groups

Condensation of 3-aminopropyltrimethoxysilane and chlorodiphenylphosphine in the molar ratio of 1:1 and 1:2 in the presence of Et3N in toluene afforded aminophosphine (CH3O)3Si(CH2)3NHPPh2 (L1) and bisphosphinoamine (CH3O)3Si(CH2)3N(PPh2)2 (L2) with methoxysilyl groups, respectively. Treatment of [(η6-C6H6)RuCl2]2 with L1 in refluxing tetrahydrofuran gave a mononuclear ruthenium phosphine complex [(η6-C6H6)RuCl2(κ1-P-L1)] (1). Reaction of [(η6-p-cymene)RuCl2]2 with L2 under the similar condition gave a dinuclear ruthenium phosphine complex [(η6-p-cymene)Ru(μ-Cl)3RuCl(κ2-P,P-L2)] (2). Complexes 1 and 2 were characterized by microanalyses, IR and NMR spectroscopies, and their structures were also established by single-crystal X-ray diffraction. Immobilization of complexes 1 and 2 on SBA-15, and characterization of these hybrid heterogeneous catalysts were studied by transmission electron microscopy (TEM), IR and low pressure N2 adsorption/desorption measurement. The heterogeneous catalysts were also briefly tested for transfer hydrogenation of acetophenone.

Mechanical and tribological properties of B-C-N coatings sliding against different wood balls

Abstract BCN coatings with different chemical compositions were prepared using RF magnetron sputtering via adjusting N2 flow. The influence of N2 flow on the bonding structure, mechanical and tribological properties of coating was studied. The structural analysis indicated the coexistence of B-N, B-C, and N-C bonds, suggesting the formation of a ternary BCN hybridization. The maximum Vickers hardness of 1614.7 HV was obtained at the low N2 flow (5 sccm), whereas the adhesion strength of BCN coatings on 316L stainless steel was improved with an increase of N2 flow. The friction behavior of BCN coatings sliding against different materials (acerbic, beech and lauan wood) was performed using ball-on-disk tribo-meter in air. The low friction coefficient was easier to obtain as sliding against hardwood i.e. acerbic balls. BCN-5 and BCN-10 coatings presented better wear resistance regardless of softwood or hardwood, whilst other two coatings were more suitable for mating softwood i.e. beech and lauan.

Insight into the Synergic Effect of Fe-SSZ-13 Zeolite and FeMnTiZrOx Catalyst with Enhanced Reactivity in NH3–SCR of NOx

The relatively low activity at low temperatures and poor performance at high temperatures with low N2 selectivity are the major problems of Fe-SSZ-13 zeolite and Mn-based metal oxides for NH3 selec...

Refluxed Synthesis of SBA-15 Using Sodium Silicate Extracted from Oil Palm Ash for Dry Reforming of Methane

Abstract The effects of Nickel (Ni) loading on Mesoporous Silica Barbara Amorphous (SBA-15) properties and catalytic activity with respect to dry reforming of methane were studied. The mesostucture characteristics of SBA-15 synthesized from oil palm ash (OPA) waste was proven by XRD low angle and N2 adsorption-desorption isotherms. Ni/SBA-15 was prepared by the sol gel method that favours metal dispersion on the SBA-15 support. The properties of the catalysts were evaluated by XRD, BET, TEM, and FTIR. The catalytic activity of catalyst was investigated in a stainless steel fixed-bed reactor at 800°C with a 1:1 ratio of CO2:CH4 feed composition. Ni supported on SBA-15 (OPA) exhibited higher CO2 and CH4 conversion with 61.07 % and 54.65 %, respectively compared to the Ni/SBA-15 (s.s) produced using commercial sodium silicate. This result demonstrated that smaller particle size of NiO with high dispersion on the SBA-15 surface, leads to higher syngas formation compared to Ni/SBA-15 (s.s). Furthermore, the appropriate interaction and synergistic effects of Ni-SBA-15, and greater NiO surface active sites were responsible for good activity in terms of CO2 and CH4 decomposition..

Evaluation of diamine-appended metal-organic frameworks for post-combustion CO2 capture by vacuum swing adsorption

Five different diamine-appended metal-organic frameworks (MOFs) that show a S-shaped CO2 isotherm are evaluated for post-combustion CO2 capture from dry flue gas using a vacuum swing adsorption process. A comprehensive simulation and optimization study using a multi-objective genetic algorithm is performed. The optimization to maximize CO2 purity and recovery showed a key link between the feed temperature, evacuation pressure and process performance. The MOFs that achieve a target CO2 purity ⩾95% and recovery ⩾90%, namely, mmen-Mn2(dobpdc) and mmen-Mg2(dobpdc) were optimized to reduce parasitic energy and increase productivity. The adsorbents, mmen-Mn2(dobpdc), mmen-Mg2(dobpdc) and Zeolite 13X showed minimum parasitic energies of 142, 152 and 167 kWhe/tonneCO2cap, respectively and maximum productivities of 0.4, 0.45 and 0.65 molCO2m-3adss-1, respectively while achieving CO2 purity ⩾95% and recovery ⩾90%. The possible low N2 affinity and the unique shape of the CO2 isotherm were found to be key reasons for a lower energy consumption.

Secondary electron emission characteristics of TiN coatings produced by RF magnetron sputtering

Multipactor, a frequent detrimental effect in space high power systems, can degrade the performance of space microwave components or even cause devastation. Surface coatings with a low secondary electron yield (SEY) have been verified to mitigate multipactor efficiently, and some literature indicates that titanium nitride (TiN) coating is an excellent multipactor suppressor due to its recognized low SEY, whereas so far, the theoretical analysis for interpreting secondary electron emission (SEE) characteristics of TiN coatings is scarce. In this work, we experimentally and theoretically investigate the SEE characteristics of TiN coatings. We fabricate seven TiN coatings at different N2 concentrations by RF sputtering. The microscopic analysis indicates that the nanostructured TiN coatings are more likely to be formed at low N2 concentration, inversely, the compact TiN films are more likely to be formed at high N2 concentration. The SEE measurement shows that the nanostructured TiN coatings are more efficient to trap electrons than the compact TiN films do. Furthermore, via measuring resistivity, we find a novel regularity that the variation in true SEY largely depends on the resistivity for compact TiN films. Namely, the true SEY of compact TiN films linearly decreases as their resistivity exponentially declines. Then, we establish an equation to describe the true SEY as a function of resistivity via applying the semiconductor conductivity theory to Dionne's SEE model. The equation qualitatively interprets the experimental regularity. This work presents a probability to control the SEE level of TiN coatings by adjusting resistivity and is of significance to comprehend the SEE of semiconductors.

Buildup of Abiotic Oxygen and Ozone in Moist Atmospheres of Temperate Terrestrial Exoplanets and Its Impact on the Spectral Fingerprint in Transit Observations

Abstract We investigate the abiotic production of oxygen and its photochemical byproduct ozone through water vapor photolysis in moist atmospheres of temperate terrestrial exoplanets. The amount of water vapor available for photolysis in the middle atmosphere of a planet can be limited by an atmospheric cold-trap, the formation of which largely depends on the amount of noncondensable gases. We study this effect using a photochemical model coupled to a 1D radiative-convective equilibrium model in atmospheres with N2, CO2, and H2O as the main constituents. We find that in atmospheres with a low N2 inventory, water vapor mixing ratios in the middle atmosphere can be more than two orders of magnitude higher compared to atmospheres with an Earth-like N2 inventory. Without a strong surface sink, the noncondensable oxygen can build up rapidly, drying out the upper atmosphere. With a moderate surface sink, the planet can approach a steady state with significant oxygen mixing ratios in which oxygen production is balanced by surface uptake. We use a radiative transfer model to study the spectroscopic fingerprint of these atmospheres in transit observations. Spectral signatures of abiotic oxygen and ozone can be of comparable magnitude as in spectra of Earth seen as an exoplanet. Middle atmospheric water vapor is unlikely to be a usable indicator of the abiotic origin of oxygen because of the influence of oxygen on the water vapor distribution. This suggests that atmospheric oxygen and ozone cannot be used as binary bioindicators and that their interpretation will likely require atmospheric and planetary models.

Ps four-wave mixing measurements of electric field in a ns pulse discharge in a hydrogen diffusion flame

Time-resolved electric field in ns pulse discharge plasmas generated in room air and in an atmospheric pressure hydrogen diffusion flame has been measured by ps four-wave mixing, for plane-to-plane electrode geometry. Electric field is put on the absolute scale using the Laplacian field measured before breakdown. The results show that peak electric field during breakdown in the flame, approximately 40 kV/cm, is significantly lower compared to that in room air, 75 kV/cm, due to higher temperature of combustion products. In both cases, peak electric field is higher compared to DC breakdown field. Both in air and in the flame, the electric field follows the applied voltage before breakdown and decreases rapidly after breakdown, due to charge separation and plasma self-shielding. The electric field in air is compared with the predictions of an analytic model of ns pulse breakdown, showing good agreement between the predicted and the measured breakdown field. The model also predicts earlier breakdown as well as breakdown voltage reduction as the temperature is increased, in qualitative agreement with the experimental data. The use of the present ps four-wave mixing diagnostics for measurements of electric fields below ∼20 kV/cm in atmospheric pressure flames is challenging, due to low signal-to-noise. The sensitivity of the present diagnostics is controlled by the high temperature and low N2 fraction in the combustion product mixture, as well as by the limited bandwidth of the Stokes beam generated by the stimulated Raman cell, which provides access only to several rotational levels of nitrogen molecules. The present diagnostics will have much better sensitivity in high-pressure flames, since the four-wave mixing signal scales as the squared number density of nitrogen.

Influence of Water Immersion on Pore System and Methane Desorption of Shales: A Case Study of Batu Gajah and Kroh Shale Formations in Malaysia

The influence of water on the pore system and gas desorption in shale remains an open question that is not yet fully understood. In this study, we present the effect of water on the shale pore system and recovered desorbed gas through a series of measurements on shale samples. We utilized the Brunauer-Emmett-Teller (BET) low pressure N2 adsorption and Field Emission Scanning Electron Microscopy (FE-SEM) to observe and analyze the effects of water immersion and moisture on the pore system of shale samples from Batu Gajah (BG) and Kroh shale formations in Malaysia. The impact of water on desorption was then measured using the United States former Bureau of Mines (USBM) modified method. The results showed that the micropore and mesopore volumes of the Batu Gajah (BG) and Kroh (KH) shale samples were reduced by 64.84% and 44.12%, respectively, after the samples were immersed in water. The BET-specific surface area declined by 88.34% and 59.63% for the BG and KH sample, respectively. Desorption results showed that the methane desorbed volume was (KH: 1.22 cc/g, BG: 0.94 cc/g) for the water immersed sample, and (KH: 0.72 cc/g, BG: 0.60) for the equilibrated sample. The difference can be attributed to the proportion of the organic (total organic carbon) and inorganic (clay) content found in the two shale samples. The total organic carbon (TOC) existing in the KH sample was 12.1 wt %, which was greater than the organic carbon content of the BG sample (2.1 wt %). The clay content was found to be more dominant in the BG shale when compared to the KH shale.

Pore Characteristics of the Fine‐Grained Tight Reservoirs in the Yabulai Basin, Northwestern China

This work investigated the pore structure characteristics and reservoir features of the finegrained tight reservoirs in the lower member of the Xinhe Formation (J2x1) in the Xiaohu subsag, Yabulai Basin based on core samples through various techniques. Interbedded silt/fine sandstones and mudstones are developed in the study area. Scanning electron microscopy (SEM) images were used to delineate different types of pores, including primary intergranular pores, secondary intergranular and intragranular pores, organic pores and fractures. The pore types were distinguished by pore size, pore area, location and formation process. The pore radii of the fine‐grained rocks range from 1 nm to 1.55 μm, mainly concentrated between 5 and 300 nm by low pressure N2 adsorption and MICP analyses. The pore structure parameters of pore throat size and pore throat sorting coefficient are both positively correlated with porosity, while pore throat sorting coefficient has a negative correlation with permeability. The pore structures of the studied samples are much related to the mineral type and content and grain size, followed by TOC content. In these rocks with relatively low TOC and low maturity, the rigid minerals protect pores with pressure shadow from collapse, and dissolution‐related pores contribute a lot to inorganic porosity. In contrast, these rocks with abundant TOC contain a large number of organic pores. The permeability of the fine‐grained tight reservoir is mainly dominated by larger pore throats, while a large number of small pores (mostly &lt;0.1 μm) contribute considerably to porosity. These results have deepened our understanding of the interbedded fine‐grained tight reservoirs and can be applicable to fine‐grained reservoirs in a similar setting.

Selective release of less defective graphene during sliding of an incompletely reduced graphene oxide coating on steel

Recently, graphene has been gaining a lot of attention as a coating material that can be effectively utilized in reducing friction and wear of sliding components. In order to fully exploit the lubricious properties of graphene, the variation in the structure of the coating as sliding proceeds against a counter surface needs to be understood clearly. In this study, the structural evolution during sliding of an incompletely reduced graphene oxide (rGO) coating deposited on the 304 stainless steel by an electrodynamic spraying process was investigated. Experimental results showed that this coating possessed a low friction coefficient, below 0.05, under either low humidity air or dry N2 gas condition. The micro-Raman and XPS analyses systematically revealed that less defective graphene structure was selectively released at the center region of the wear track. It was determined that the redistribution of graphene with different structures within the wear track was induced by frictional interaction at the sliding interface. Furthermore, it was determined that the degree of release of less defective graphene structure was proportional to both the applied normal force and sliding cycles.

Ag-Cu based catalysts for the selective ammonia oxidation into nitrogen and water vapour

XRD, BET, H2-TPR, UV–vis-DRS, XPS and XAFS were used to characterize a series of Ag and/or Cu – Ag (1–5%), Cu (10–15%) or Ag-Cu (1–1, 1–10, 1.5–10, 5–5% of metal) – supported on γ-Al2O3. Correlation between physicochemical properties, catalytic activity and selectivity in NH3-SCO were thoroughly investigated. Silver species mainly in the form of Ag2O on the Ag/Al2O3 catalysts led to enhanced activity together with drop in N2 selectivity with increasing silver loading up to 5%. A mixture of CuO and CuAl2O4 formed on the Cu/Al2O3 catalysts. Easily reducible highly dispersed CuOx promoted the activity of the catalysts, while bulk CuOx and CuAl2O4 decreased N2 selectivity up to 500 °C. The activity of all Cu-containing materials was inferior to Ag-containing ones. Thus, the gap between the high conversion temperature over Cu/Al2O3 and low N2 selectivity over Ag/Al2O3 was bridged by applying the Ag-Cu/Al2O3 catalysts, with the optimum loading of 1.5 and 10 wt.% for silver and copper, respectively. NH3-TPD, NH3-TPSR and in situ FTIR were used to determine the in situ selective catalytic reduction (i-SCR) mechanism over 1.5% Ag/Al2O3, 10% Cu/Al2O3 and 1.5% Ag-10% Cu/Al2O3 respectively. The i-SCR mechanism involved the partial oxidation of NH3 into NOx species, along with adsorbed NOx species interacting with adsorbed ammonia (NHx species) and being reduced to reaction products.

Pore geometrical complexity and fractal facets of Permian shales and coals from Auranga Basin, Jharkhand, India

The pore system is a significant factor for the hydrocarbon generation, storage and production. Several studies had been carried earlier by distinguished researchers on pore system characterization, where little information regarding a thermally immature basin has been discussed so far. To understand these, total fifty-one samples including 41-shales and 10-coals are taken for study from Barakar (L.Sakmarian-Kungurian) Formation of Auranga basin to investigate the pore characteristics of a low mature substance. This work provides information regarding a low mature basin having oil generation potential. For this, authors have carried low pressure N2 sorption, FE-SEM/EDX with rock eval pyrolysis, total organic carbon (TOC), ash yield, vitrinite reflectance and clay content. The low-pressure N2 sorption: BET (Brunauer-Emmett-Teller) and BJH (Barrett-Joyner-Halenda) are employed to analyze the pore size, area, geometry and its distribution. Shale samples have shown variation in the specific surface areas (BET) and pore volume from 7.43 to 30.36 m2/g and 0.019–0.069 cm3/g respectively; whereas coal samples exhibits these properties ranging from 3.13 to 17.2 m2/g and 0.08–0.31 cm3/g respectively. Here, two kinds of desorption curve have been observed: (a) sub-hysteresis types H2′ where rapid desorption (lacking a plateau at high pressure) indicating pipette shaped pore (b) hysteresis type H3 having slow rate of desorption suggesting slit shaped pore. The subtype H2′ i.e. lacking the plateau at high pressure has been distinguished under H2 hysteresis. The dominance of mesopores to macropores are deduced from BJH and presence of micropores were also observed in few samples from t-plot method. The Type II isotherms are observed dominantly in shales and few coal samples (27-shales; 3-coals) whereas Type IV isotherms (13 shales; 7 coals) are mainly noticed in coals and in limited number of shales. Moreover, the total organic carbon (TOC) content of the shale and coal samples ranges from 1.35 to 29.42 wt% and 32.38–63.46 wt% respectively. Tmax [temperature under S2 to release maximum amount of pyrolyzate from the kerogen under rock eval pyrolysis (REP)] range from 409 to 468 °C and 420–426 °C of shales and coals respectively indicating of immature to early mature stage of the sample. The TOC normalized-BET (BET*) in relation to ash yield exhibits the significance of mineral matter in the shales for pore formation. The relation of pyrolysis parameters (S1and S2) with BET* gives the indication of bitumen retention in the pore spaces of organic matter, which reduces their surface area in coals. Fractal geometry of the samples were also studied. The surface fractal dimensions viz. D1 (P/Po = 0.0–0.5) and D2 (P/Po = 0.5–1.0) both are calculated for the basin. The D1 (pore surface) varies from 1.9888 to 2.5530 and 1.8190–2.4430 for shales and coals respectively pointing towards surface heterogeneity and ruggedness of the surface favorable for increasing the adsorption capability. However, D2 (pore structure) for the shales and coals are placed in the range of 2.570–2.759 and 2.6150–2.7530 respectively indicating large heterogeneity of the pore structure causing high capillary condensation that reduces the adsorption ability. The FE-SEM with EDX study supports the analysis of pore structure, characteristics and fractal behaviour of shales and coals.

Nitrogen Fixation by Trichodesmium and unicellular diazotrophs in the northern South China Sea and the Kuroshio in summer

Distribution of diazotrophs and their nitrogen fixation activity were investigated in the northern South China Sea (nSCS) and the Kuroshio from July 16th to September 1st, 2009. N2 fixation activities in whole seawater and <10 μm fraction at the surface were measured by acetylene reduction assay. Higher activities were observed at the East China Sea (ECS) Kuroshio and the nSCS shelf. The nSCS basin showed a low N2 fixation activity. The <10 μm fractions (unicellular diazotrophs) contributed major portion to the whole-water activity in the survey time, indicating that nanoplanktonic cyanobacterias were the major diazotrophs in the survey area. Daily N2 fixation rates of Trichodesmium ranged from 0.11 to 9.83 pmolNtrichome−1 d−1 with an average of 4.03 pmolNtrichome−1 d−1. The Luzon Strait and the ECS Kuroshio had higher N2 fixation rates of Trichodesmium than the nSCS shelf and basin. Calculated activities of Trichodesmium at most stations were moderately low compared with that of the whole-water. The contribution of N2 fixation by the whole-water to primary production ranged from 1.7% to 18.5%. The estimated amount of new nitrogen introduced by Trichodesmium contributed up to 0.14% of the total primary production and 0.41% of the new production in the Luzon Strait.

Geochemical and petrophysical characteristics of Permian shale gas reservoirs of Raniganj Basin, West Bengal, India

Thick shale horizons of Permian age emerged as the potential source of gas through primary investigation, and resulted into the first Indian pilot-scale gas recovery demonstration project in the Raniganj basin. However, the relation of geochemical properties with shale pore matrix, porosity and permeability mechanism are yet to be evaluated for better dealing the phenomena of diffusion, transport and gas recovery. In this study, the analyses like proximate, Rock-Eval, TOC, VRo, low pressure N2 sorption, porosity, permeability, SEM-EDX and image processing have been carried out. The values of S1, S2, TOC and Tmax indicated fair to excellent source rock potential of the shales having type III/IV kerogens prone to thermal gas genesis. The low pressure N2 desorption curve of Raniganj Formation shales shows the Type H3 hysteresis comprising slit-shaped pores. The Barren Measures shales have Type H2 and H3 hysteresis patterns specifying to ink bottle-shaped pores and slit-shaped pores. Whereas, the oldest Barakar Formation shales are having ink bottle-shaped pores caused due to blocking effect. The slit-shaped pores favour the pore network and characteristically excellent for the flow of gas. The results of SEM-EDX are indicating alteration stability in the order of O<C<Si<Al<Fe<K<Na<Ca following the trend of least to strong weathering (Barakar<Barren Measures<Raniganj). The siliciclastic facies (Al-Si-Fe) signifying massive and laminated shale beds deposited under fluvio-lacustrine palaeoenvironment favouring alteration and accumulation of K-feldspar and aluminous minerals to clay.The increasing Tmax values with a centric decrease in porosity and permeability, specifying the role of devolatilization, disintegration and blocking of pore spaces/openings is a function of the thermal gradient. The linear evolution of multipoint BET surface area with increasing porosity suggests that the porosity values from 2.0 to 6.5% mainly corresponds to pore size of 3.0–11.0nm. Similarly, the inverse relationship between average pore size and porosity attributed to a greater contribution of smaller pores in total porosity. The pore network model derived through the SEM image processing has shown two types of connectivity - i) various pore sizes of diverse pore throats with dual opening directions, and ii) interlinked large and small pores obeying similar normal distributions. The Barren Measures shales have shown higher pore connectivity than the Raniganj and Barakar Formation shales.

Molybdenum nitrides: a study of synthesis variables and catalytic performance in acetylene hydrogenation

We have examined the catalytic action of β- and γ-Mo2N in the partial hydrogenation of acetylene. The influence of variations in GHSV (230–1600 min−1), feed composition (5–30% v/v N2/H2), heating rate (0.1–5 K min−1) and isothermal hold (1–7 h at 933 K) on nitride structural properties has been assessed. At ≥ 2 K min−1, β-Mo2N (≤ 15 m2 g−1) consisting of small crystallites (< 5 μm) was generated. At ≤ 0.5 K min−1, γ-Mo2N with a platelet morphology and surface area ≥ 45 m2 g−1 was formed. High GHSV, low N2 feed content and a prolonged isothermal hold served to increase γ-Mo2N area (to 135 m2 g−1). Lower alkene selectivity and a twofold higher specific (per m2) acetylene hydrogenation rate were recorded for β-Mo2N and linked to higher surface Mo/N ratio (from XPS). Olefin selectivity for both nitrides was greater than that reported for Pd catalysts. Moreover, we recorded negligible green oil formation in reactions over γ-Mo2N.

Hierarchical Porous Carbon Nanospheres for Efficient Removal of Toxic Organic Water Contaminants of Phenol and Methylene Blue

Hierarchical porous carbon nanospheres were synthesized by a hydrothermal process at 130 °C/24 h using different triblock copolymers such as F108 (PEO133PPO50PEO133; PEO, poly(ethylene oxide); PPO, poly(propylene oxide)), F127 (PEO106PPO70PEO106), and L64 (PEO13PPO30PEO13) as soft templating agents. Characterization of the samples was carried out by low angle XRD, Raman spectra, FESEM, TEM, and N2 adsorption–desorption studies. The BET surface area of the samples was in the range 600–750 m2/g comprised of micropores and mesopores. Nanospherical particles of size range 60–100 nm were formed. The synthesized samples were used for the removal of phenol and methylene blue (MB), the toxic organic contaminant in water. The maximum adsorptions of 98.9 and 100% were observed within 10 min for phenol and MB, respectively. For different soft templates, the adsorption capacity of the samples followed in the order CF108 > CF127 > CL64, which was affected by the textural properties of the corresponding samples. Select...

Effect of atmosphere on the fabrication of Si2N2O matrix composites

Si2N2O matrix composites were fabricated by solid/gas reaction in air or N2 atmosphere. The effects of atmosphere on the phase and microstructure of the composites were investigated. The reaction mechanism of Si2N2O system was discussed by analysing the variation of the Gibbs free energy with temperature. The effect of N2 and air on sintering of Si2N2O matrix composites was discussed in relation to observed kinetics and thermodynamic calculations. The results showed that gradient structure of Si2N2O matrix composites were obtained in N2 atmosphere. While high N2 concentration was useful for the formation of the pure ?-Si3N4 ceramics, low N2 concentration was proposed to form the pure Si2N2O ceramics. However, in the air atmosphere, structure of the Si3N4/SiO2 composites is homogeneous without the gradient structure appearing. Its composition is a little different as the O2 concentration changes.