The Influence of the Desulfovibrio desulfuricans 14 ATCC 27774 on the corrosion of mild steel

The involvement of sulphate‐reducing bacteria (SRB) in microbially influenced corrosion (MIC) of steel and the serious implications associated with their presence in industrial environments have long been known and extensively described. Desulfovibrio desulfuricans ATCC 27774 is an interesting metabolic case of SRB, as it can use both sulphate and nitrate as respiratory substrates during lactate oxidation. This strain has been extensively studied from both a biochemical and structural point of view but, so far, restricted information is available concerning its role in MIC. This work describes a comparative study of the corrosive aggressivity of ATCC 27774 strain towards mild steel when grown either in lactate/sulphate or lactate/nitrate media. The carbon source and electron acceptor's consumption rates were analysed and the metabolic features were correlated with weight loss measurements and SEM observations.     

Stability and stabilisation of penicillin acylase

The stability of an oligomeric enzyme, penicillin acylase, was studied in aqueous media. The enzyme was produced by mutant cells of Escherichia coli ATCC 9637, extracted from the periplasmic space by osmotic shock and further purified using a pseudo‐affinity adsorption process. Enzyme stabilisation attempts were performed with salts, alcohols and sugars. The highest levels of retained activity were obtained in the presence of 15% (w/v) ammonium or sodium sulfate. A kinetic model was proposed to describe the inactivation of penicillin acylase, taking into account results obtained in stability assays performed at different temperatures and with different enzyme concentrations. According to this model, the inactivation of penicillin acylase involves an intermediary active precursor of the enzyme, formed prior to dissociation into sub‐units. © 1999 Society of Chemical Industry     

Iron ore pellet drying assisted by microwave: A kinetic evaluation

Drying is a critical process step to achieve excellent pellet quality in pelletizing process. The complexity and energy consumption toward moisture removing, especially for highly hydrated iron ore, increased the need for breakthrough enhancements to this process. The present study has evaluated kinetics parameters of the moisture release from iron ore green pellet using energy transmitted through microwave (frequency of 2.45 GHz). The influence of pellet size and output power on the moisture effective diffusivity (D_eff) and the drying activation energy (E_a) were evaluated. The results make possible to compare the cutting-edge approach with traditional convective drying. Pellet physical quality was investigated through the green crushing strength (GCS), which shows smooth reduction in earlier stages, however not affecting the final dry GCS results. Bonded hematite reduction and calcination of goethite was identified at the microstructure through reflected light microscopy, SEM showed micro cracks formation in several grains.     

Mechanical Properties and Microstructural Characterization of Aged Nickel-based Alloy 625 Weld Metal

Metallurgical and Materials Transactions A - The aim of this work was to evaluate the different phases formed during solidification and after thermal aging of the as-welded 625 nickel-based alloy,...     

Mechanical properties of amorphous nanosprings

Helical amorphous nanosprings have attracted particular interest due to their special mechanical properties. In this work we present a simple model, within the framework of the Kirchhoff rod model, for investigating the structural properties of nanosprings having asymmetric cross section. We have derived expressions that can be used to obtain the Young's modulus and Poisson's ratio of the nanospring material composite. We also address the importance of the presence of a catalyst in the growth process of amorphous nanosprings in terms of the stability of helical rods.     

The influence of rolling temperature on texture evolution and variant selection during α → β → α phase transformation in Ti–6Al–4V

The role of starting texture in variant selection has been studied during α → β → α transformation in Ti–6Al–4V. By hot rolling at different temperatures followed by recrystallization, material with either a strong basal texture or a strong transverse texture was generated. Subsequently, both conditions were heat-treated above the β transus followed by slow cooling. The degree of variant selection was assessed by comparing the strength of the measured and predicted α texture from high temperature β texture, assuming equal occurrence of all possible variants during β → α transformation. It was found that, even though the material rolled originally at 800 °C displayed a stronger α texture after β heat treatment, it was the material rolled originally at 950 °C that showed greater variant selection. The variant selection mechanism is discussed in terms of the generated β texture and common 〈1 1 0〉 poles in neighbouring β grains selecting a similar α variant on both sides of the prior β grain boundary. Predictions of possible 〈1 1 0〉 pole misorientation distributions for the two investigated β textures showed that the combination of texture components generated during rolling Ti–6Al–4V at 950 °C increases the likelihood of having β grain pairs with closely aligned (1 1 0) planes compared to rolling at 800 °C. Therefore, it can be proposed that avoiding the generation of certain combinations of β texture components during thermomechanical processing has the potential for reducing variant selection during subsequent β heat treatment.     

Deformation behaviour of an advanced nickel-based superalloy studied by neutron diffraction and electron microscopy

Deformation mechanisms under tensile loading at room temperature have been studied in a polycrystalline nickel-based superalloy containing close to 50 vol.% γ′. In order to identify the effect of γ′ particle size on deformation mechanisms, model microstructures with unimodal γ′ size distributions were developed. The investigations were carried out by combining in situ loading experiments using neutron diffraction and two-site elasto-plastic self-consistent plasticity modelling with detailed post-mortem electron microscopy. The microscopy work also includes results for samples strained at 500 °C. During early plastic deformation, the diffraction data demonstrate that γ and γ′ display the same elastic strain response, indicating that at this stage γ′ is cut by dislocations regardless of the γ′ particle size. Scanning electron microscopy studies showed an abundance of shearing processes in all three microstructures, hence supporting the conclusions drawn from the diffraction experiment. As the material is further deformed, elastic load transfer from γ to γ′ was observed in the medium (130 nm) and coarse (230 nm) γ′ microstructures but not in the fine (90 nm) γ′ microstructure. The load transfer can be explained by assuming that Orowan looping becomes an additional operative deformation mode. Transmission electron microscopy confirmed that in the fine γ′ microstructure deformation takes place by strongly coupled dislocations cutting the γ′, while the medium and coarse γ′ microstructures showed additional signs of Orowan looping.     

Evaluation of solar photo-Fenton parameters on the pre-oxidation of leachates from a sanitary landfill

The main purpose of this work is to study the treatment of a leachate after preliminary aerated lagooning by a solar photo-Fenton process, using a photocatalytic reactor with compound parabolic collectors (CPCs). The influence of different process parameters in the reaction rate was evaluated, such as, the type of acid used in the acidification step (H₂SO₄, HCl, H₂SO₄ + HCl); type of iron salt (FeSO₄, FeCl₃) and respective iron concentration (60, 80, 100 and 140 mg Fe²⁺/L); temperature; and ratio of illuminated to total volume (25 L/35 L; 25 L/72 L). DOC abatement in the acidification procedure is independent of the type of acid used and temperature, and is related principally with the precipitation of humic acids. The use of HCl alone or in combination with H₂SO₄ leads to a substantially increase of the chloride ions, leading to the formation of less reactive chloride radicals when compared with sulfate radicals, decreasing the photo-Fenton reaction rate. The use of ferrous ions instead of ferric ions influenced positively the photo-Fenton reaction. Meteorological conditions favoring higher temperature of the leachate enhance the photo-Fenton reaction. Alternating dark and illumination intervals has shown a negligible effect on the illumination time needed to achieve the same mineralization, indicating that the Fenton process that takes place in dark zones is not efficient, even in the degradation of intermediate compounds resulting from the light-enhanced reaction. According to biodegradability tests, the optimum energy dose, necessary to obtain a biodegradable effluent, is 57.4 kJ_UV/L, consuming 120 mM of H₂O₂ and leading to a final DOC of 284 mg/L which corresponds to approximately 66% of mineralization.     

CdSe/CdTe interface band gaps and band offsets calculated using spin–orbit and self-energy corrections

We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe, and their interface band alignments on the CdSe in-plane lattice parameters. For this, we employed the LDA-1/2 self-energy correction scheme [L.G. Ferreira, M. Marques, L.K. Teles, Phys. Rev. B 78 (2008) 125116] to obtain corrected band gaps and band offsets. Our calculations include the spin–orbit effects for the bulk cases, which have shown to be of importance for the equilibrium systems and are possibly degraded in these strained semiconductors. Therefore, the SO showed reduced importance for the band alignment of this particular system. Moreover, the electronic structure calculated along the transition region across the CdSe/CdTe interface shows an interesting non-monotonic variation of the band gap in the range 0.8–1.8 eV, which may enhance the absorption of light for corresponding frequencies at the interface between these two materials in photovoltaic applications.     

Biomass briquetting and its perspectives in Brazil

A study of the status of biomass briquetting and its perspectives in Brazil was conducted including determination of the availability and characteristics of the agro-residues for briquetting. Wood residues, rice husk and coffee husk were characterized and identified as the more promising agro-residues for briquetting in the short-term in Brazil. A survey was carried out in order to determine the number of briquetting factories in Brazil, and also to determine: used briquetting technologies, briquettes production, briquettes sale prices, the status of biomass briquetting market and its future perspectives.