Thermoplastic Polyurethane Nanocomposites Produced via Impregnation of Long Carbon Nanotube Forests

TPU was infiltrated into vertically aligned, 3.5 mm‐long MWNT forests to produce continuously reinforced anisotropic nanocomposites, and thermomechanical and electrical testing has revealed multifunctionality which shows promise for numerous applications. A 1000% increase in the storage modulus at 70 °C was observed as compared to the neat TPU, and these continuously aligned composites showed electrical conductivity two orders‐of‐magnitude greater (≈1.5 S · cm^?1) than randomly aligned composites prepared using CNTs from these forests. The heightened improvement for the continuously reinforced composite appears to be owed to the extremely high aspect ratio of these CNTs and the interconnected network which remains after infiltration.

     

Survival of three Bifidobacterium animalis subsp. lactis strains is related to trans-vaccenic and α-linolenic acids contents in organic fermented milks

This study aims at relating the survival at 4 °C for 28 days in organic and conventional fermented milks of three strains of Bifidobacterium animalis subsp. lactis (BB12, B94 and BL04), in co-culture with Streptococcus thermophilus TA040 and Lactobacillus bulgaricus LB340, to milk fatty acids profile. Cultivability after 28 days of cold storage was improved in organic fermented milks as compared to conventional products, with slight differences among strains. In addition, the poly-unsaturated fatty acids fraction was higher in organic products, as well as the relative trans-vaccenic (TVA) and α-linolenic (ALA) fatty acids contents that were respectively 1.7 and 2.4 times higher in organic than in conventional fermented milks. From these results, it was concluded that elevated levels of TVA and ALA, together with a lower ratio between linoleic acid and α-linolenic acid, as found in organic products, improved the survival of the bifidobacteria during chilled storage.     

Production of Lipase from Geotrichum candidum Using Corn Steep Liquor in Different Bioreactors

The production of an extracellular lipase using corn steep liquor (CSL) as the nitrogen source in the cultivation of Geotrichum candidum NRRLY‐552 was evaluated. The optimized conditions in shake flasks were CSL, 8.0 % w/v, soybean oil, 0.6 % w/v, pH 7.0, 30 °C, 250 rpm, and 48 h, resulting in a maximum lipase productivity of 0.438 U mL^?1 h^?1(U = the amount of enzyme required to liberate 1 μmol of fatty acid per minute). Scale‐up was evaluated with airlift and stirred tank reactors; the best conditions, respectively, were 1 vvm(volume of gas per volume of medium per minute) of aeration which resulted in 0.535 U mL^?1 h^?1 (32 h) and 1 vvm and 300 rpm resulting in 0.563 U mL^?1 h^?1 (16 h). To facilitate downstream processes, lipase production was also evaluated using CSL previously clarified with activated charcoal resulting in 0.275 U mL^?1 h^?1 (24 h) using 12 % (w/v) of clarified CSL in shake flasks. The obtained results showed that CSL leads to similar productivity compared to peptone using the same microorganism under similar conditions. In addition the cost of fermentation medium using CSL is much lower because it is a very inexpensive by‐product from corn processing.     

Drying behavior and decay resistance of rubberwood from steamed log and presteamed lumber

The objective of this study was to evaluate the effect of log steaming and steaming prior to drying singly and both treatments together on the drying behavior and decay resistance of Hevea brasiliensis wood (rubberwood). Logs with a diameter of 34.6?±?4.4?cm were used. Half of the logs were kept in their original condition, and the other half were steamed at 90°C for 36?h. Later, the logs were cut into flat sawn boards. Half of the boards were kept in their original condition, and the other half were presteamed at 90°C for 3?h after 1?h of heating-up. These boards were dried in a drying kiln. The drying defects, drying time, drying rate, and decay resistance of wood to the Pycnoporus sanguineus fungus were determined. The results showed that the steaming is not suitable for decreases in the time and the drying rates of this kind of wood, and it neither reduces the drying defects of boards. Furthermore, these treatments adversely affected the decay resistance of rubberwood to P. sanguineus fungi.     

Sol-gel synthesis of triclinic CoV2O6 polycrystals

In this paper, a new chemical route synthesis for γ-CoV₂O₆ is proposed. Based on the CoO-V₂O₅ phase diagram a study of temperature and calcination times for pure γ-CoV₂O₆ obtainment is described. X-ray diffraction and Raman spectroscopy experiments revealed the triclinic crystals structure belonging to P-1 spatial group. FEG-SEM images showed that the resulting grains present elongated shape. Rietveld analysis revealed a crystalline anisotropy with preferential crystallographic orientation in the [2 0 ? 1] and [1 3 0] planes. The calculated mean crystallite size evidences that the crystallite dimensions are significantly different in the parallel and perpendicular directions. The magnetic properties measurements evidenced an antiferromagnetic transition at 7?K and a detailed view of the magnetization isotherms confirmed a noticeable step-like behavior below T_N, characteristic of field-induced transitions.     

Blocking effect in promising proton conductors based on Ba3Ca1.18Nb1.82-xRxO9-δ (R = Y3+, Gd3+, Sm3+, Nd3+) ordered perovskites for PC-SOFCs

High proton conductivity and good chemical stability are keys to development of new electrolytes for PC-SOFCs as the next-future energy generation systems. However, the extensive use of new polycrystalline materials as solid electrolytes is still avoided, since the grain boundary response usually leads to a decrease in total conductivity due to electrical blocking effect. Here, we present our results on the space-charge modeling of impedance spectroscopy data obtained for Ba₃Ca_1.18Nb_1.82-xR_xO_9-δ proton conducting ceramics, where x?=?0, 0.30 and R =?Y³⁺, Gd³⁺, Sm³⁺, Nd³⁺ are doping agents. Non-stoichiometric barium calcium niobate perovskites have received much attention as potential solid electrolytes for proton conducting solid oxide fuel cells. We show that despite their increased grain conductivity, the doped ceramics possess Schottky barriers that are higher than those observed for undoped Ba₃Ca_1.18Nb_1.82O_9-δ. In view of the space-charge model, proton depletion at the space-charge layer is the reason for the reduction of grain boundary conductivity in the doped compositions. Our findings are important for the understanding of proton conduction mechanisms in polycrystalline materials, which may allow future optimization of new doped electrolytes based on barium calcium niobate perovskites.     

Nitrous oxide fluxes in a Brazilian clayey oxisol after 24 years of integrated crop-livestock management

Integrated crop-livestock systems have been recently adopted in several agricultural regions of Brazil. Studies involving the effect of adopting integrated systems on greenhouse gas mitigation are essential for choosing sustainable agricultural systems. In this study, the emissions of nitrous oxide in a crop-livestock system (4-year crop/pasture rotation) compared with two continuous crop (CC) areas under conventional and no-tillage management were investigated. The treatments consisted of continuous cropping under no-tillage (CC-NT), continuous cropping with annual heavy disc harrow (CC-CT), an integrated crop-livestock system under no-tillage (CLS-NT) and native Cerrado as a reference. Considering the cumulative N₂O emissions in a year, the CC-CT emitted 2.55 kg N-N₂O ha^?1, higher than the Cerrado, which emitted 0.55 kg N-N₂O ha^?1. All the agricultural systems emitted more N₂O than the Cerrado, however, the two conservation systems CC-NT and CLS-NT had lower emissions than the CC-CT, and were responsible for 1.90 and 1.52 kg N-N₂O ha^?1, respectively. In the agroecosystems, the highest N₂O fluxes were observed after fertilization and rainfall events. In the CC systems, N₂O emissions were greater than in the integrated system during the sorghum/off-season period, but in the CC-CT emissions were greater than in CC-NT. During the soybean cycle no differences in emissions were observed between both CC systems, which surpassed that in CLS-NT that was occupied by Brachiaria pasture. The annual cumulative N₂O emissions in CLS-NT were close to that observed in the Cerrado indicating this system to be an agricultural practice with potential to mitigate N₂O emissions.     

Modelling the effect of HAZ undermatching on the crack-tip stress distribution in idealized welds

In order to study the influence of the heat-affected zone softening on the fracture behaviour of welds with cracks in the weld metal centre line, a large variety of weld geometries and undermatch conditions of the heat affected zone mechanical properties, relative to the weld metal and base material, were addressed in this study. With this aim, the opening stress distribution in notched welded specimens was analysed using the numerical simulation of the three-point bending test. The numerical results show a reduction in the stress levels ahead of the crack tip for welded specimens with severe heat-affected zone undermatch. The stress distribution is strongly influenced by the crack position relative to the weld material/heat-affected zone interface, independently of heat-affected zone width.     

New petroleum absorbers based on cardanol‐furfuraldehyde magnetic nanocomposites

Cardanol‐furfuraldehyde/maghemite composites were prepared through a bulk polymerization aiming to produce magnetic green resins able to absorb petroleum spilled on the water. Several techniques such as Fourier transform infrared spectroscopy, ultraviolet–visible spectrophotometry, wide angle X‐ray scattering, and small angle X‐ray scattering were used in the characterization of the materials. In addition, magnetic force and oil removal capability tests were also performed. Obtained materials presented a good magnetic force allied with a considerable oil removal capability: each gram of the resin was able to remove 10g of petroleum from the water. Therefore, the easy and simple production process presented is a promising tool for oil spill cleanup process. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Polycyclic Aromatic Hydrocarbons from Candiota (South Brazilian) Coal Extracts

The bitumen composition of Candiota coal (south Brazil) was investigated. Coal bitumen was produced by Soxhlet extraction using toluene. Two chromatographic techniques were tested for bitumen fractionation: adsorption liquid chromatography on silica (ALCS) and adsorption liquid chromatography on alumina (ALCA). Results were compared in terms of the quality and quantity of hydrocarbons isolated. Several linear saturated hydrocarbons were found in the range of 14 to 33 carbons. Pyrene, chrysene, and other polycyclic hydrocarbons with recognized mutagenic and carcinogenic properties were found in the aromatic fractions. Chromatographic methodology using alumina shows better results in the fractionation of bitumen.