Application of visible and near infrared spectroscopy in non-destructive evaluation of cement materials

In the twenty-first century, there has been rapid urbanization in economically emerging countries. Many scientific research studies have proposed methods to monitor the quality of materials used in engineering works. Quality inspections are most often made of structure-related materials such as concrete. All the concrete used in construction work is subjected to a test that breaks the samples to evaluate its final mechanical strength. In this sense, remote sensing can contribute to mapping and monitoring construction materials, allowing investigation and identification of various properties such as mechanical strength and water content in a non-destructive manner. The materials can be inspected directly on site, in a rapid, non-invasive, and inexpensive manner; this is crucial for the ongoing process of construction. The spectral behaviour of four different mechanical strengths of two cement materials based on Portland cement, cement paste, and mortar was observed using a FieldSpec® 3 spectroradiometer. The spectral curves generated by recording the reflected and absorbed electromagnetic radiation of the samples were interpreted based on the theory of vibrational and electronic spectroscopy. The objective of this work is to show a novel technique for assisting in the analysis of solid samples using visible and near infrared spectroscopy. Through this study, a spectral contrast between different samples of the paste and mortar was found. Besides, it was possible to detect the presence and the corresponding proportion of water in the samples. Wavelet analysis enabled records of statistical evidence of spectral contrast, and showed that the depth of water absorption features is inversely proportional to compressive strength in the cement materials under study. This work is innovative, because there are no studies in the literature on the application of this technique as an aid tool for differentiating compressive strengths of Portland-cement-based materials.     

Fuel gas from a wood waste carbonization reactor

The production of fuel gas from wood wastes in a full scale carbonization reactor of simple design was studied. The production of methane and the approach to equilibrium to the water-gas shift reaction were experimentally correlated with the operating conditions. The heating value of the gas produced is comparable to that of typical air blown coal and biomass gasifiers, and may be improved by pre-drying the solid feed and by operating the reactor at lower temperatures.     

Polymer blends based on PEO and starch: Miscibility and spherulite growth rate evaluated through DSC and optical microscopy

The miscibility and PEO spherulite growth rate in PEO/starch blends (starch from cassava) were evaluated using the depression in the melting point (by DSC) and optical polarized microscope, respectively, and compared to pure PEO. The PEO/starch blend ratio changed from 100/0 to 60/40 (weight/weight). The starch induces changes in PEO crystallization on PEO/starch blends but the crystallization rates do not change linearly to the blend ratio. For 90/10, 80/20, 70/30, 65/35 and 60/40 ratios, lower values for the equilibrium melting temperature were observed as compared to the pure PEO. The obtained interaction parameter value was ? 0.25 by the use of Nishi–Wang equation. The depression in the equilibrium melting temperatures and the negative value for the polymer–polymer interaction parameter suggest that the blends are miscible in the molten state in the range of investigated ratios, except for the 95/05 ratio in which the equilibrium melting temperature increased relative to the pure PEO. The miscibility should be due to the H-bonds among the hydroxyl groups from starch and oxygen atoms of repeat units of PEO.     

Optical behaviour of Er doped rutile by ion implantation

Rutile single crystals were implanted at room temperature with fluences of 5 × 10¹⁵ Er⁺/cm² ions with 150 keV energy. Rutherford backscattering/channeling along the 0 0 1 axis reveals complete amorphization of the implanted region. Photoluminescence reveals the presence of an optical centre close to the intra-ionic emission of Er³⁺ in the as-implanted samples. After annealing at 800 °C in air no changes were observed in the aligned RBS spectrum. On the contrary, annealing in reducing atmosphere (vacuum) induces the epitaxy of the damage layer. These results are unexpected, since for implantations of other ions under the same conditions, epitaxial recrystallization of the damage region occurs at this temperature. On the other hand, photoluminescence studies show the presence of new Er-related optical centres with high thermal stability in the samples annealed under oxidizing conditions. Annealing at 1000 °C in vacuum leads to the complete recrystallization of the damaged region. At this temperature a large fraction of Er segregates to the surface.     

Nitrous oxide emission and ammonia volatilization induced by vinasse and N fertilizer application in a sugarcane crop at Rio de Janeiro,Brazil

In Brazilian sugarcane plantations, fertilization with vinasse, supplemented or not with mineral fertilizer, is a common practice. But little is known about the effects of this application on N losses, especially those forms of N which give rise to greenhouse gas emissions. The aim of this study was to quantify N₂O and NH₃ emissions from soil after vinasse application and urea fertilizer addition and to examine the possible impact adding vinasse before or after urea. Two experiments were conducted under greenhouse conditions and one in the field with treatments of vinasse and urea fertilizer, either alone, or in sequence. The highest proportions of N emitted as N₂O were registered in the vinasse treatment, which amounted to 15 % of the N applied in the first greenhouse experiment, and 2.5 % in the field experiment. With respect to the losses by NH₃ volatilization, urea was the only treatment where this process was significant. N₂O emission from vinasse was 2.5 %, somewhat above the default emission factor of 1 % of the IPCC. N₂O emissions from urea were also variable, but emission factors registered were still well below the default IPCC factor for organic residues. The order of addition of urea and vinasse had little effect on NH₃ volatilization in the field, but there were evidences it was important for N₂O.     

Study of the thermomechanical and electrical properties of conducting composites containing natural rubber and carbon black

This work describes the preparation and characterization of composite materials obtained by the combination of natural rubber (NR) and carbon black (CB) in different percentages, aiming to improve their mechanical properties, processability, and electrical conductivity, aiming future applications as transducer in pressure sensors. The composites NR/CB were characterized through optical microscopy (OM), DC conductivity, thermal analysis using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMA), thermogravimetry (TGA), and stress–strain test. The electrical conductivity varied between 10^?9 and 10 S m^?1, depending on the percentage of CB in the composite. Furthermore, a linear (and reversible) dependence of the conductivity on the applied pressure between 0 and 1.6 MPa was observed for the sample with containing 80 wt % of NR and 20% of CB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Chemically modified babassu coconut (<Emphasis Type="Italic">Orbignya sp.)</Emphasis> biopolymer: characterization and development of a thin film for its application in electrochemical sensors

The babassu coconut is a plant very abundant in northeast of Brazil and other countries, and any part of plant and fruit becomes residue. In this study, babassu mesocarp (Orbignya sp) (BM) was chemically modified with phthalic anhydride (BMPA) to increase its solubility in an aqueous medium, and thus facilitate its processing in the form of thin films. The reaction of modification of the babassu mesocarp with phthalic anhydride (PA), obtaining BMPA, was confirmed by FTIR, XRD, TG/DTG, Zeta Potential and SEM analysis, from the differences in the bands of the FTIR spectra, increase in crystallinity, new thermal profile, changes in zeta potential value and morphology, respectively. The thin monolayer films of BM and BMPA were produced by the self-assembly monolayer (SAM) technique, and adsorbed onto conductive glass substrates (tin-doped indium oxide, ITO). The electroactive properties of these thin films were evaluated by cyclic voltammetry (CV). BM exhibited a pair redox pair process of +0.57 V(oxidation) and?+?0.19 V (reduction) for BM. In BMPA these redox processes were observed at +0.37 V (oxidation) and 0.24 V vs. ECS (reduction), verifying that both BM and BMPA are electroactive materials that can be used in the construction of sensor platforms, without the necessity of being conjugated with other electroactive materials, such as conductive polymers, metal phthalocyanines, or dyes. Furthermore, under the experimental conditions used, the BMPA presented a more reversible redox process and higher electrochemical stability in comparison to BM. This effect occurs because BMPA has higher solubility in aqueous media, which favors the preparation of films with smaller grain sizes compared to BM films, as observed by Atomic Force Microscopy (AFM). This study showed that BMPA is a new material with potential for applications in electrochemical sensors.

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Graphical abstract Obtaining and modifying babassu mesocarp for the electrochemical studies

     

SEM study of the morphology of asymmetric cellulose acetate membranes produced from recycled agro-industrial residues: sugarcane bagasse and mango seeds

Cellulose, obtained both from sugarcane bagasse and mango seeds, was used for synthesizing cellulose acetate in order to produce asymmetric membranes. These were compared to membranes of commercial cellulose acetate (Rhodia). All produced membranes were asymmetric, characterized by the presence of a dense skin and a porous support. Differences regarding the morphology of the surfaces as well as of the porous support can be noticed. Scanning Electron Microscopy (SEM) showed that the morphology of the superficial layer, responsible for transport, depends on the different lignin content of the starting material and also on the viscosity average molecular weight of the cellulose acetates produced from sugarcane bagasse, mango seed, and Rhodia’s commercial cellulose acetate.