Influence of carbon source and inoculum type on anaerobic biomass adhesion on polyurethane foam in reactors fed with acid mine drainage

This paper analyzes the influence of carbon source and inoculum origin on the dynamics of biomass adhesion to an inert support in anaerobic reactors fed with acid mine drainage. Formic acid, lactic acid and ethanol were used as carbon sources. Two different inocula were evaluated: one taken from an UASB reactor and other from the sediment of a uranium mine. The values of average colonization rates and the maximum biomass concentration (C(max)) were inversely proportional to the number of carbon atoms in each substrate. The highest C(max) value (0.35 g TVS g(-1) foam) was observed with formic acid and anaerobic sludge as inoculum. Maximum colonization rates (v(max)) were strongly influenced by the type of inoculum when ethanol and lactic acid were used. For both carbon sources, the use of mine sediment as inoculum resulted in a v(max) of 0.013 g TVS g(-1) foam day(-1), whereas 0.024 g TVS g(-1) foam day(-1) was achieved with anaerobic sludge. (C) 2011 Elsevier Ltd. All rights reserved.

Influence of chloride ion concentration and temperature on the electrochemical properties of passive films formed on a superduplex stainless steel

Polarization measurements were conducted to monitor the corrosion behavior of superduplex stainless steel ASTM A995M-Gr.SA/EN 10283-Mat#1.4469(GX2CrNiMo26-7-4) when exposed to a) an electrolyte containing 22,700 parts per million (ppm) of chloride ions at seven different temperatures and b) an electrolyte at 25 GC and different chloride ion concentrations (5800, 22,700, 58,000 and 80,000 ppm of Cl(-)). The polarization curves indicate that the passive films formed are only slightly affected by NaCl concentration, but the pitting potential decreases drastically increasing the temperature, in particular >60 degrees C. The image analysis of the microstructure after potentiodynamic polarization showed that the pitting number and size vary in function of the temperature of the tested medium. Nyquist diagrams were determined by electrochemical impedance spectroscopy to characterize the resistance of the passive layer. According to Nyquist plots, the arc polarization resistance decreases increasing the temperature due to a catalytic degradation of the oxide passive films. (C) 2009 Elsevier Inc. All rights reserved.

Influence of the Solvent Evaporation Rate on the Crystalline Phases of Solution-Cast Poly(Vinylidene Fluoride) Films

The influence of the solvent-evaporation rate on the formation of of. and P crystalline phases in solution-cast poly(vinylidene fluoride) (PVDF) films was systematically investigated. Films were crystallized from PVDF/N,N-dimethylformamide solutions with concentrations of 2.5, 5.0, 10, and 20 wt % at different temperatures. During crystallization, the solvent evaporation rate was monitored in situ by means of a semianalytic balance. With this system, it was possible to determine the evaporation rate for different concentrations and temperatures of the solution under specific ambient conditions (pressure, temperature, and humidity). Fourier-Transform InfraRed spectroscopy with Attenuated Total Reflectance revealed the P-phase content in the PVDF films and its dependence on previous evaporation rates. Based on the relation between the evaporation rate and the PVDF phase composition, a consistent explanation for the different amounts of P phase observed at the upper and lower sample surfaces is achieved. Furthermore, the role of the sample thickness has also been studied. The experimental results show that not only the temperature but also the evaporation rate have to be controlled to obtain the desired crystalline phases in solution-cast PVDF films. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 785-791, 2010

Influence of EVA and acrylate polymers on some mechanical properties of cementitious repair mortars

In repair works of reinforced concrete, patch repairs tend to crack in the interfacial zone between the mortar and the old concrete. This occurs basically due to the high degree of restriction that acts on a patch repair. For this reason, the technology of patch repair needs to be the subject of a discussion involving professionals who work with projects, construction maintenance and mix proportioning of repair mortars. In the present work, a study is presented on the benefits that the ethylene vinyl acetate copolymer (EVA) and acrylate polymers can provide in the mix proportioning of a repair mortar with respect to compressive, tensile and direct-shear bond strength. The results indicated that the increase in bond strength and the reduction in the influence of the deficiency in Curing conditioning are the main contributions offered by the polymers studied here. (C) 2009 Elsevier, Ltd. All rights reserved.

Influence of the slice position on chloride migration tests for concrete in marine conditions

Chloride migration tests are used to measure the concrete capacity to inhibit chloride attack. Many researchers carry out this test in a slice of concrete extracted from the central part of cylindrical specimens, discarding about 75% of the concrete used to mold the specimens. This fact generated the question: would it be possible to extract more slices from a same specimen without losing the confidence in the results? The main purpose of this work is to answer this question. Moreover, another aim of this study was to show the difference of chloride penetration between finished faces and the formwork surfaces of concrete beams and slabs. The results indicated that it is possible to use more slices of a single specimen for a chloride migration test. Moreover, it was demonstrated that there is a significant difference of chloride penetration between the finished surface and the formwork surface of the specimens. (C) 2008 Elsevier Ltd. All rights reserved.

The influence of moisture on the deformability of cement-polymer adhesive mortar

Adhesive mortars are widely used to set porcelain stoneware tiles on buildings because their bond strength and flexibility properties increase the cladding serviceability. However, their long-term performance is not well understood, mainly the degradation of the polymeric matrix. The influence of moisture content on the flexibility of six adhesive mortars is investigated, based on standard EN 12002. Four of them have defined formulations and the other two are commercial and are widely used to set porcelain stoneware tiles on building facades in Brazil. The results show that moisture content above 6% is sufficient to reduce 50% of the mortar deformability, but that the drying process allows it to recover to a value similar to that prior to saturation; a logarithmic function best fits the correlation between moisture content and flexibility; water immersion increases matrix rigidity. It is suggested that standards should consider flexibility tests on both dried and wet samples as a requirement for polymer-modified mortars. (C) 2010 Elsevier Ltd. All rights reserved.

A Study of Influence of Configurations of the Windings on the Performance of Single Phase Induction Motor with Capacitor Start

The single phase induction motors needs two stator windings to produce rotating magnetic field : one main winding and the other auxiliary winding. The aim of the auxiliary winding is to create the rotating electromagnetic field when the machine is started-up and is afterwards turned off, generally through the centrifugal switch coupled together with the shaft of the machine rotor. The main purpose of this document is to evaluate the influence that the two windings have on the external characteristics of the single phase induction motor. For this purpose, two different kinds of windings were carried out and simulated, with the proposal to obtain some benefits. The main winding and the auxiliary winding were prepared and mounted on a prototype. The simulation was done via software based FEM, to make the extraction and results analysis possible. This results are shown at the end this document.

Study of the influence of simultaneous variation of magnetic material microstructural features on domain wall dynamics

The magnetic Barkhausen noise (MBN) is a phenomenon sensitive to several kinds of magnetic material microstructure changes, as well as to variations in material plastic deformation and stress. This fact stimulates the development of MBN-based non-destructive testing (NDT) techniques for analyzing magnetic materials, being the proposition of such a method, the main objective of the present study. The behavior of the MBN signal envelope, under simultaneous variations of carbon content and plastic deformation, is explained by the domain wall dynamics. Additionally, a non-destructive parameter for the characterization of each of these factors is proposed and validated through the experimental results. (C) 2010 Elsevier B.V. All rights reserved.

Influence of hardness of the harder body on wear regime transition in a sliding pair of steels

In the unlubricated sliding wear of steels the mild-severe and severe-mild wear transitions have long been investigated. The effect of system inputs such as normal load, sliding speed, environment humidity and temperature, material properties, among others, on those transitions have also been studied. Although transitions seem to be caused by microstructural changes, surfaces oxidation and work-hardening, some questions remain regarding the way each aspect is involved. Since the early studies in sliding wear, it has usually been assumed that only the material properties of the softer body influence the wear behavior of contacting surfaces. For example, the Archard equation involves only the hardness of the softer body, without considering the hardness of the harder body. This work aims to discuss the importance of the harder body hardness in determining the wear regime operation. For this, pin-on-disk wear tests were carried out, in which the disk material was always harder than the pin material. Variations of the friction force and vertical displacement of the pin were registered during the tests. A material characterization before and after tests was conducted using stereoscopy and scanning electron microscopy (SEM) methods, in addition to mass loss, surface roughness and microhardness measurements. The wear results confirmed the occurrence of a mild-severe wear transition when the disk hardness was decreased. The disk hardness to pin hardness ratio (H(d)/H(p)) was used as a criterion to establish the nature of surface contact deformation and to determine the wear regime transition. A predominantly elastic or plastic contact, characterized by H(d)/H(p) values higher or lower than one, results in a mild or severe wear regime operation, respectively. (c) 2009 Elsevier B.V. All rights reserved.

Influence of parameters of the HVOF thermal spray process on the properties of multicomponent white cast iron coatings

High velocity oxi-fuel (HVOF) thermal spray process has been used in order to deposit a new alloy known as multicomponent white cast iron. The coatings were characterized in terms of macrostructure, phase composition, porosity and hardness. Coating characteristics and properties were found to be dependent on the particles size range, spray distance, gases flow rate and oxygen to propane ratio. For set of parameters utilized in this job a narrow particle size range between 20 and 45 gm with a spray distance of 200 mm and oxygen to propane ratio of 4.6 are the preferred coating parameters. Coating porosity of 0.9% and hardness of 766 HV were obtained under these conditions. (c) 2007 Elsevier B.V. All rights reserved.

Influence of Microstructures on Polarization Resistance and Hydrogen-Induced Cracking of a Micro-Alloyed Steel Submitted to Different Cooling Rates

The effect of different microstructures on the polarization resistance (Rp) and the hydrogen-induced cracking (HIC) of a micro-alloyed steel austenitized and submitted to different cooling rates was studied. Samples 19.1 x 6 x 2 mm, containing the whole thickness of the plate were extracted from a 20 mm plate and heat treated on a quenching dilatometer, were submitted to Rp and HIC corrosion tests. Both Rp and HIC tests followed as close as possible ASTM G59 and NACE standard TM0284-2003, in this case, modified only with regard to the size of the samples. Steel samples transformed from austenite by a slow cooling (cooling rate of 0.5 degrees C.s(-1)) showed higher susceptibility to hydrogen-induced cracking, with large cracks in the middle of the sample propagating along segregation bands, corresponding to the centerline of the plate thickness. For cooling rates of 10 degrees C.s(-1), only small cracks were found in the matrix and micro cracks nucleated at non-metallic inclusions. For higher cooling rates (40 degrees C.s(-1)) very few small cracks were detected, linked to non-metallic inclusions. This result suggests that structures formed by polygonal structures and segregation bands (were cutectoid microconstituents predominate) have higher susceptibility to HIC. Structures predominantly formed by acicular ferrite make it difficult to propagate the cracks among non-oriented and interlaced acicular ferrite crystals. Smaller segregation bands containing eutectoid products also help inhibit cracking and crack propagation; segregation bands can function as pipelines for hydrogen diffusion and offer a path of stress concentration for the propagation of cracks, frequently associated to non-metallic inclusions. Polarization resistance essays performed on the steel in theas received condition, prior to any heat treatment, showed larger differences between the regions of the plate, with a considerably lower Rp in the centerline. The austenitization heat treatments followed by cooling rates of 0.5 e 10 degrees C.s(-1) made more uniform the corrosion resistance along the thickness of the plate. The effects of heat treatments on the corrosion resistance are probably related to the microconstituent formed, allied to the chemical homogenization of the impurities concentrated on the centerline of the plate.

Influence of the Type of Quaternary Ammonium Salt Used in the Organic Treatment of Montmorillonite on the Properties of Poly(Styrene-co-Butyl Acrylate)/Layered Silicate Nanocomposites Prepared by In Situ Miniemulsion Polymerization

Hybrid latices of poly(styrene-co-butyl acrylate) were synthesized via in situ miniemulsion polymerization in the presence of 3 and 6 wt % organically modified montmorillonite (OMMT). Three different ammonium salts: cetyl trimethyl ammonium chloride (CTAC), alkyl dimethyl benzyl ammonium chloride (Dodigen), and distearyl dimethyl ammonium chloride (Praepagen), were investigated as organic modifiers. Increased affinity for organic liquids was observed after organic modification of the MMT. Stable hybrid latices were obtained even though miniemulsion stability was disturbed to some extent by the presence of the OMMTs during the synthesis. Highly intercalated and exfoliated polymer-MMT nanocomposites films were produced with good MMT dispersion throughout the polymeric matrix. Materials containing MMT modified with the 16 carbons alkyl chain salt (CTAC) resulted in the largest increments of storage modulus, indicating that single chain quaternary salts provide higher increments on mechanical properties. Films presenting exfoliated structure resulted in the largest increments in the onset temperature of decomposition. For the range of OMMT loading studied, the nanocomposite structure influenced more significantly the thermal stability properties of the hybrid material than did the OMMT loading. The film containing 3 wt % MMT modified with the two 18 carbons alkyl chains salt (Praepagen) provided the highest increment of onset temperature of decomposition. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 3658-3669, 2011

Influence of Water Content, Time, and Temperature on the Rheological Behavior of Polyethylene Terephtalate

In this work, the main factors affecting the rheological behavior of polyethylene terephtalate (PET) in the linear viscoelastic regime (water content, time delay before test, duration of experiment, and temperature) were accessed. Small amplitude oscillatory shear tests were performed after different time delays ranging from 300 to 5000 s for samples with water contents ranging from 0.02 to 0.45 wt %. Time sweep tests were carried out for different durations to explain the changes undergone by PET before and during small amplitude oscillatory shear measurements. Immediately after the time sweep tests, the PET samples were removed from the rheometer, analyzed by differential scanning calorimetry and their molar mass was obtained by viscometry analysis. It was shown that for all the samples, the delay before test and residence time within the rheometer (i.e. duration of experiment) result in structural changes of the PET samples, such as increase or decrease of molar mass, broadening of molar mass distribution, and branching phenomena. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 3525-3533, 2010

Influence of the rubbery phase on the crystallinity and thermomechanical properties of poly(3-hydroxybutyrate)/elastomer blends

Poly(3-hydroxybutyrate) (PHB) is a very promising biopolymer. In order to improve its processability and decrease its brittleness, PHB/elastomer blends can be prepared. In the work reported, the effect of the addition of a rubbery phase, i.e. ethylene - propylene-diene terpolymer (EPDM) or poly(vinyl butyral) (PVB), on the properties of PHB was studied. The effects of rubber type and of changing the PHB/elastomer blend processing method on the crystallinity and physical properties of the blends were also investigated. For blends based on PHB, the main role of EPDM is its nucleating effect evidenced by a decrease of crystallization temperature and an increase of crystallinity with increasing EPDM content regardless of the processing route. While EPDM has a weak effect on PHB glass transition temperature, PVB induces a marked decrease of this temperature thank to its plasticizer that swells the PHB amorphous phase. A promising solution to improve the mechanical properties of PHB seems to be the melt-processing of PHB with both plasticizer and EPDM. In fact, the plasticizer is more efficient than the elastomer in decreasing the PHB glass transition temperature and, because of the nucleating effect of EPDM, the decrease of the PHB modulus due to the plasticizer can be counterbalanced. (C) 2010 Society of Chemical Industry

Influence of Temperature, Basiscity and Particle Size on MnO Reduction

The aim of this work is to study MnO reduction by solid carbon. The influence of size of carbon particles, slag basicity, and bath temperature on MnO reduction was investigated. Fine Manganese ore particles were used as a source of MnO. Three sizes of carbon particles were used; 0.230 mm, 0.162 mm and 0.057 mm, binary basicity of 1 and 1.5 and temperatures of 1550, 1550 and 1600 degrees C. Curves were drawn for Mn content in the bath as a function of time and temperature for the several studied parameters. The MnO reduction rates were determined using these data. [doi:10.2320/matertrans.M2011007]