Greenhouse gas emissions from soil under maize–soybean intercrop in the North China Plain

Intercrop systems can exhibit unique soil properties compared to monocultures, which influences the microbially-mediated processes leading to greenhouse gas emissions. Fertilized intercrops and monocultures produce different amounts of N₂O, CO₂ and CH₄ depending on their nutrient and water use efficiencies. The objective of this study was to compare the fluxes and seasonal emissions of N₂O, CO₂, and CH₄ from a maize–soybean intercrop compared to maize and soybean monocultures, in relation to crop effects on soil properties. The experiment was conducted during 2012, 2013 and 2014 at the WuQiao Experimental Station in the North China Plain. All cropping systems received urea-N fertilizer (240 kg N ha^?1 applied in two split applications). The cropping systems were a net source of CO₂ and a net sink of CH₄, with significantly (P < 0.05 in 2012) and numerically (2013 and 2014) lower N₂O flux and smaller seasonal N₂O emissions from the maize–soybean intercrop than the maize monoculture. The proportion of urea-N lost as N₂O was lower in the maize–soybean intercrop (1.6% during the 3-year study) and soybean monoculture (1.7%), compared to maize monoculture (2.3%). Soybean reduced the soil NO₃^?–N concentration and created a cooler, drier environment that was less favorable for denitrification, although we cannot rule out the possibility of N₂O reduction to N₂ and other N compounds by soybean and its associated N₂-fixing prokaryotes. We conclude that maize–soybean intercrop has potential to reduce N₂O emissions in fertilized agroecosystems and should be considered in developing climate-smart cropping systems in the North China Plain.     

Season and location–specific nitrous oxide emissions in an almond orchard in California

Almonds are an important commodity in California and account for around 15% of the state’s fertilizer nitrogen (N) consumption. Motivated by strong correlations typically observed between fertilizer N inputs and emissions of the potent greenhouse gas and ozone depleting molecule nitrous oxide (N₂O), this study aimed to characterize spatial and temporal patterns in N₂O emissions in an almond orchard under typical agronomic management. N₂O fluxes were measured for a total of 2.5 years, including 3 growing seasons and 2 dormant seasons. Measurements targeted two functional locations, defined as tree rows and tractor rows. In conjunction with the flux measurements, we determined driving variables including soil ammonium (NH₄ ⁺) and nitrate (NO₃ ^?), dissolved organic carbon (DOC), soil water-filled pore space (WFPS), soil pH, air temperature and precipitation. Cumulative annual N₂O emissions were low (0.65 ± 0.07 and 0.53 ± 0.19 kg N₂O–N ha^?1 year^?1 in year 1 and 2, respectively), likely due to the coarse soil texture and microject sprinkler irrigation and fertigation system. Emission factors (EF), conservatively calculated as the ratio of N₂O emitted to fertilizer N applied, were 0.25 ± 0.03% and 0.19 ± 0.07% for year 1 and 2, respectively, which is below the IPCC EF range of 0.3–3%. Correlation analyses between N₂O and driving variables suggested that overall N₂O production was limited by microbial activity and nitrification was likely the major source process, but specific drivers of N₂O emissions varied between seasons and functional locations.     

Covalently intercalated graphene oxide for oil–water separation

We report the transformation of hydrophilic graphene oxide (GO) sheets into superhydrophobic nanomaterial by direct esterification with epoxy-functionalized polyhedral oligomeric silsesquioxane (ePOSS). The covalently functionalized GO–ePOSS composite shows superhydrophobicity with a water/air contact angle of ∼145°. The highest dispersion limits for GO in selected organic solvents are obtained in the literature. The dispersion of GO–ePOSS can be extended to solvents with Hansen solubility parameters as low as 3.4. Efficient oil–water separation is also demonstrated by using a GO–ePOSS membrane.     

Perovskite oxide and polyazulene–based heterostructure for high–performance supercapacitors

Several types of electrode materials have been developed for high–performance supercapacitors. Most of the relevant studies have focused on the discovery of new atomic structures and paid limited attention to the effect of heterostructures in supercapacitor electrodes, which has long hindered the fundamental understanding of the use of hybrid materials in supercapacitors. In this study, a novel heterostructure based on perovskite oxide (LaNiO₃) nanosheets and polyazulene was synthesized. The as–prepared heterostructure–based supercapacitor exhibited a specific capacitance of up to 464 F g⁻¹ at a high current density of 2 A g⁻¹ in 1–ethyl–3–methylimidazolium tetrafluoroborate. In a symmetric supercapacitor, this heterostructure delivered an energy density of up to 56.4 Wh kg⁻¹ at a power density of 1100 W kg⁻¹. Both LaNiO₃ and polyazulene contributed pseudocapacitance and dominated the performance. Unexpectedly, electric double–layer capacitance was found to contribute in this system. Density functional theory calculations indicated that the advantage of the high electrical conductivity of the heterostructure benefited the supercapacitor operation. Electrochemical quartz crystal microbalance analysis revealed that the fast ion flux and adsorption boosted performance. The high intrinsic electrical conductivity and improved stability make this heterostructure a promising electrode material candidate for supercapacitors.     

Polyaniline–antimony oxide composites for effective broadband EMI shielding

Conducting polyaniline (PAni)–antimony trioxide (Sb₂O₃) composites with different weight percentages (wt%) of Sb₂O₃ in PAni have been synthesized by in situ chemical oxidative polymerization. The composites were structurally and morphologically characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Measurements of electromagnetic interference (EMI) shielding, complex permittivity and microwave absorbing as well as reflecting properties of the composites were carried out in the frequency range of 8–18 GHz, encompassing the microwave X and Ku bands of practical relevance. All the computations are based on microwave scattering parameters measured by transmission line waveguide technique. It is observed that the presence of Sb₂O₃ in the PAni matrix affects the electromagnetic shielding and dielectric properties of the composites at microwave frequencies. The composites have shown better shielding effectiveness (SE) in both the X (SE in the range ?18 to ?21 dB) and Ku (?17.5 to ?20.5 dB) bands. ε′ and ε′′ values of the PAni–Sb₂O₃ composites are in the range of 64–37 and 63–30, respectively, in the frequency range of 8–18 GHz. Dielectric measurements indicated the decrease in dielectric constant with the increase in wt% of Sb₂O₃. The results obtained for the reflection and absorption coefficients indicated that PAni–Sb₂O₃ composites exhibit better electromagnetic energy absorption throughout the X and Ku bands. The results indicated that PAni–Sb₂O₃ composites can be used as potential microwave absorption and shielding materials.     

One-pot synthesis of core–shell-structured tin oxide–carbon composite powders by spray pyrolysis for use as anode materials in Li-ion batteries

Core–shell-structured tin oxide–carbon composite powders with mixed SnO₂ and SnO tetragonal crystals are prepared by one-pot spray pyrolysis from a spray solution with tin oxalate and polyvinylpyrrolidone (PVP). The aggregate, made up of SnO_x nanocrystals (several tens of nanometers), is uniformly coated with an amorphous carbon layer. The initial discharge capacities of the bare SnO₂ and SnO_x–carbon composite powders at a current density of 1 A g⁻¹ are 1473 and 1667 mA h g⁻¹, respectively; their discharge capacities after 500 cycles are 78 and 1033 mA h g⁻¹, respectively. The SnO_x–carbon composite powders maintain their spherical morphology even after 500 cycles. On the other hand, the bare SnO₂ powder breaks into several pieces after cycling. The structural stability of the SnO_x–carbon composite powders results in a low charge transfer resistance and high lithium ion diffusion rate even after 500 cycles at a high current density of 2 A g⁻¹. Therefore, the SnO_x–carbon composite powders have superior electrochemical properties compared with those of the bare SnO₂ powders with a fine size.     

Reduced graphene oxide–gold nanoparticle membrane for water purification

The reduced graphene oxide–gold nanoparticle (rGO–Au NP) membranes are prepared by vacuum filtration method. The sizes of the Au NPs on the surface of the rGO are about 8–10 nm, and the lattice spacing of Au NPs is 0.0241 nm, which is relative to the cubic lattice of the gold crystal. The layer-by-layer stacking structure of rGO–Au NP membrane can be observed clearly by field emission scanning electron microscopy. The water flux of the rGO–Au NP membrane is as high as 204.1 L m^?2 h^?1 bar^?1, and its retention for Rhodamine B (RhB) is as high as 99.79%.     

Tin–Zinc oxide composite ceramics for selective CO sensing

Composite metal oxide gas sensors were intensely studied over the past years having superior performance over their individual oxide components in detecting hazardous gases. A series of pellets with variable amounts of SnO₂ (0–50 mol%) was prepared using wet homogenization of the component oxides leading to the composite tin-zinc ceramic system formation. The annealing temperature was set to 1100 °C. The samples containing 2.5 mol% SnO₂ and 50 mol% SnO₂ were annealed also at 1300 °C, in order to observe/to investigate the influence of the sintering behaviour on CO detection. The sensor materials were morphologically characterized by scanning electron microscopy (SEM). The increase in the SnO₂ amount in the composite ceramic system leads to higher sample porosity and an improved sensitivity to CO. It was found that SnO₂ (50 mol%) - ZnO (50 mol%) sample exhibits excellent sensing response, at a working temperature of 500 °C, for 5 ppm of CO, with a fast response time of approximately 60 s and an average recovery time of 15 min. Sensor selectivity was tested using cross-response to CO, methane and propane. The results indicated that the SnO₂ (50 mol%)-ZnO (50 mol%) ceramic compound may be used for selective CO sensing applications.     

Green electrospun nanocuprous oxide–poly(ethylene oxide)–silk fibroin composite nanofibrous scaffolds for antibacterial dressings

Cuprous oxide (Cu₂O) nanoparticles have attracted extensive attention because of their excellent optical, catalytic, antibacterial, and antifungal properties and low cost. Nano-Cu₂O–poly(ethylene oxide) (PEO)–silk fibroin (SF) composite nanofibrous scaffolds (CNSs) were fabricated through green electrospinning to impart excellent antibacterial properties onto nanofibrous scaffolds. Scanning electron microscopy revealed that the nanofibers became more nonuniform and appeared more and more as beads in the nanofibers with increasing nano-Cu₂O concentration, and no obvious morphological changes were observed after 75% EtOH vapor treatment. Transmission electron microscopy and X-ray photoelectron spectroscopy demonstrated that nano-cuprous oxide (nano-Cu₂O) was successfully loaded into the PEO–SF nanofibers. Fourier transform infrared–attenuated total reflectance spectroscopy results indicate that nano-Cu₂O did not induce SF conformation from random coils to β sheets. The SF conformation converted from random coils to β sheets after 75% EtOH vapor treatment. The results of water contact angle testing and swelling property measurement clarified that nano-Cu₂O–PEO–SF CNSs possessed outstanding hydrophilicity. Nano-Cu₂O–PEO–SF CNSs exhibited better antibacterial activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria than PEO–SF nanofibrous scaffolds, and the antibacterial activity increased with increasing nano-Cu₂O concentration. Cell viability studies with pig iliac endothelial cells demonstrated that nano-Cu₂O–PEO–SF CNSs had no cytotoxicity. Nano-Cu₂O–PEO–SF CNSs are expected to be ideal biomimetic antibacterial dressings for wound healing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47730.     

Zn–Ca–Al mixed oxide as efficient catalyst for synthesis of propylene carbonate from urea and 1,2-propylene glycol

A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of catalyst composition, basicity and reaction process parameters such as temperature, catalyst dose, molar ratio of PG to urea, purge gas flow and reaction time has been studied to find suitable reaction conditions for the PC synthesis. The PC selectivity and yield under the desired conditions could reach 98.4% and 90.8%, respectively. The best performing catalyst also exhibited a good reusability without appreciable loss in the PC selectivity and yield after five consecutive reaction runs. In addition, a stepwise reaction pathway involving a 2-hydroxypropyl carbamate intermediate was proposed for the urea alcoholysis to PC in the presence of Zn–Ca–Al catalysts, according to the time dependences of reaction intermediates and products.     

Cellulose-based formaldehyde adsorbents with large capacities: Efficient use of polyethylenimine for graphene oxide stabilization in alkaline–urea system

A cellulose-based polyethylenimine modified graphene oxide (PEI-GO) composite aerogel is fabricated through the alkaline–urea aqueous system. Inspired from the performance of nanocarriers in gene delivery, this article proposes a pathway to disperse GO in the green environment with strong electrolyte concentrations via the decorated branched PEI. The entire aqueous system shows good miscibility and stability. Meanwhile, the dynamic light scattering results indicate that PEI-GO and cellulose chains become entangled to form a new supramolecular complex in the alkaline–urea solution, and a “hand” model is devised accordingly. The efficient dispersion of PEI-GO (1–0.1%) over the entire cellulose support structure (3%) enables the resultant aerogel to exhibit a gaseous formaldehyde adsorption capacity, that is, 8.51 times greater than the pure cellulose aerogel under ambient temperatures. This dual function opens up enormous opportunities to process cellulose-based GO materials in this green and inexpensive solvent with strong electrolyte concentrations. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47860.     

Mullite interaction with bismuth oxide from minerals and sol–gel processes

Mullite compounds with bismuth oxide in the SiO₂–Al₂O₃–Bi₂O₃ ternary system were synthesized from TEOS (C₂H₅O)₄Si, aluminum nitrate Al(NO₃)₃·9H₂O and bismuth nitrate Bi(NO₃)₃. Thermal and structural transformations were studied at temperatures ranging from 1000 to 1400 °C. The coexistence of Al₄Bi₂O₉ and Bi₄Si₃O₁₂ phases at temperatures up to 1000 °C was observed in compositions containing 5–31 mol% Bi₂O₃. Mullite is observed at temperature higher than 1000 °C in composition not exceeding 5 mol% of Bi₂O₃. Corundum coexist with a liquid above 1000 °C in all compositions containing more than 5 mol% Bi₂O₃. The liquid temperature is slightly above 1000 °C for all compositions. A tentative pseudo-binary diagram mullite-Bi₂O₃ is proposed. A similar system was studied with silico-aluminate compositions containing kaolinite and muscovite minerals. The occurrence of a liquid when Bi₂O₃ is added highly favors the mullite growth at temperature below 1200 °C. It is favored by local concentrations at interfaces of a transient liquid phase, which enhance the mobility of species.     

Reduced graphene oxide for Li–air batteries: The effect of oxidation time and reduction conditions for graphene oxide

Reduced graphene oxide (rGO) has shown great promise as an air-cathode for Li–air batteries with high capacity. In this article we demonstrate how the oxidation time of graphene oxide (GO) affects the ratio of different functional groups and how trends of these in GO are extended to chemically and thermally reduced GO. We investigate how differences in functional groups and synthesis may affect the performance of Li–O₂ batteries. The oxidation timescale of the GO was varied between 30 min and 3 days before reduction. Powder X-ray diffraction, micro-Raman, FE-SEM, BET analysis, and XPS were used to characterize the GO’s and rGO’s. Selected samples of GO and rGO were analyzed by solid state ¹³C MAS NMR. These methods highlighted the difference between the two types of rGO’s, and XPS indicated how the chemical trends in GO are extended to rGO. A comparison between XPS and ¹³C MAS NMR showed that both techniques can enhance the structural understanding of rGO. Different rGO cathodes were tested in Li–O₂ batteries which revealed a difference in overpotentials and discharge capacities for the different rGO’s. We report the highest Li–O₂ battery discharge capacity recorded of approximately 60,000 mAh/g_carbon achieved with a thermally reduced GO cathode.     

Alumina-supported manganese- and manganese–palladium oxide catalysts for VOCs combustion

Alumina-supported manganese- and palladium–manganese oxide catalysts were prepared and tested in the combustion of formaldehyde. Total combustion of formaldehyde/methanol was achieved at 220 °C over a 18.2% Mn/Al₂O₃ catalyst. This temperature decreased either to 90 or 80 upon adding 0.1% or 0.4% Pd, respectively, to the base 18.2% Mn/Al₂O₃ catalyst. The combined use of X-ray diffraction, temperature-programmed reduction and photoelectron spectroscopy (XPS) techniques revealed that a Mn⁴⁺/Mn³⁺ oxide(s) and PdO_x species are present on the surface of the fresh catalysts and remain along the catalytic reaction.     

Formaldehyde emissions from particle board made with phenol–urea–formaldehyde resin prepared by different synthesis methods

This paper suggests the optimum NAF resin preparation to reduce the quantity of pollutant emissions from the particle boards by using PUF resin. The pollutant emissions performance of the prepared NAF resin was evaluated by comparison with eMDI resin. Each PF and PUF resin was made by variation of the molar ratio and synthesis methods according to order of addition of the basic products. In addition, after verifying the properties of the resins, the quantity of pollutant emitted from boards made with the PUF resins were evaluated. Of the cases of boards made with each resin, the formaldehyde emission was the lowest for PB #7. The eMDI resin used in this board showed good quality as an eco-friendly resin, because it had less than half the formaldehyde emission of the other formaldehyde-based resins. In addition, the mechanical properties of the particle board met the KS criteria; therefore, there should be no restriction on use in manufactured goods.     

Emulsion–ion extraction technique for synthesis of hollow bicomponent oxide microspheres

Abstract

H ollow ox ide microspheres in the bicomponent systems Al₂O₃-28 wt-%SiO₂ (AS) ( mullite) , Al₂O₃- 13 wt-%T iO₂ (AT) , and Z rO₂-10 wt-%Y₂O₃ ( Z Y) were prepared by the emulsion-ion extraction technique. Monodisperse microsphere formation was found to depend on the experimental parameters adopted during ion ex traction and the surfactant concentration present in the emulsion system. Powder characteristics were investigated using X-ray diffraction, optical and scanning electron microscopy, and particle size analysis. The gel microspheres in the AS, AT , and ZY systems started crystallising at about 900, 800, and 400 °C respectively. The oxide microspheres were mostly spherical in morphology and the sphericity was retained even after calcination at 1300 °C for 1 h. Formation of hollow microspheres with a single spherical cavity was identified by SEM . All oxide microspheres calcined at 1300 °C for 1 h ex hibited a particle size distribution within the range 5-60 μm, the average size ( d₅₀) varying from 19 to 22 μm. BCT / 537     

Hypochlorite generation on Ru–Pt binary oxide for treatment of dye wastewater

Ruthenium–platinum binary oxides [(Ru + Pt)O_x] were coated on titanium substrates by thermal decomposition. The surface morphologies and elemental analyses of these electrodes were examined by means of scanning electron microscopy. The electrochemical behaviour was characterized by cyclic voltammetry (CV) and linear scanning voltammetry (LSV). The effects of electrolyte conditions on the current efficiency (CE) of hypochlorite production on binary (Ru + Pt)O_x electrodes and the treatment of a high salt-containing dye wastewater using this hypochlorite were also investigated. The highest CE for hypochlorite production occurred on the RP1 (20 mol% Pt in precursor) electrode. The major factors influencing CE for hypochlorite production were the electrolyte flow rate, current density and chloride ion (C1^–) concentration. The RP1 electrode exhibited the best removal of organics and chromophoric groups in the dye wastewater. On this electrode, better removal of organics and chromophoric groups was obtained at 300 mA cm^–2. The colour of black–red dye wastewater became light yellow when a charge of 13.2 A h was passed while the COD of the wastewater decreased from 10 500 to 1250 mg L^–1.