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Artificial cementation of granular soils results in improved stabilization, increased stiffness, and greater mechanical strength. The porosity index and volumetric cement content η / C i v a is presented as a key measure to study the evolution of different soil stabilization types. However, this index had not been previously studied or adjusted for sands in Colombia. Therefore, this study evaluates the applicability of the η / C i v a index on unconfined compressive strength (q u ) and stiffness ( G o ), complemented by microstructural analysis, in four sandy soils from Luruaco (Atlántico), Lorica (Córdoba), Medellín (Antioquia), and Bogotá D.C. The soils were stabilized with Type III Portland cement in dosages of 3%, 5%, 7%, and 9%, and subjected to UCS, ultrasound, and SEM-EDS tests after a curing period of 7 days. It was found that increasing cement content results in higher q u values for the samples, and higher molding density also leads to higher q u values. Additionally, the grain size distribution influenced the adjustment of parameter "a". In the sands from Bogotá and Lorica, with high uniformity, the value of "a" was 1.00. In contrast, mineralogy and particle shape played a predominant role in the sands from Medellín and Luruaco, where the coefficient of uniformity is higher, suggesting a possible inverse relationship between particle angularity and the value of "a". [ABSTRACT FROM AUTHOR]

The particular properties of graphene oxide (GO) make it a material with great technological potential, so it is of great interest to find renewable and eco-friendly sources to satisfy its future demand sustainably. Recently, agricultural waste has been identified as a potential raw material source for producing carbonaceous materials. This study explores the potential of cashew nut shell (CNS), a typically discarded by-product, as a renewable source for graphene oxide synthesis. Initially, deoiled cashew nut shells (DCNS) were submitted to pyrolysis to produce a carbonaceous material (Py-DCNS), with process optimization conducted through response surface methodology. Optimal conditions were identified as a pyrolysis temperature of 950 °C and a time of 1.8 h, yielding 29.09% Py-DCNS with an estimated purity of 82.55%, which increased to 91.9% post-washing. Using a modified Hummers method, the Py-DCNS was subsequently transformed into graphene oxide (GO-DCNS). Structural and functional analyses were carried out using FTIR spectroscopy, revealing the successful generation of GO-DCNS with characteristic oxygen-containing functional groups. Raman spectroscopy confirmed the formation of defects and layer separations in GO-DCNS compared to Py-DCNS, indicative of effective oxidation. The thermogravimetric analysis demonstrated distinct thermal decomposition stages for GO-DCNS, aligning with the expected behavior for graphene oxide. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) further corroborated the morphological and compositional transformation from DCNS to GO-DCNS, showcasing reduced particle size, increased porosity, and significant oxygen functional groups. The results underscore the viability of cashew nut shells as a sustainable precursor for graphene oxide production, offering an environmentally friendly alternative to conventional methods. This innovative approach addresses the waste management issue associated with cashew nut shells and contributes to developing high-value carbon materials with broad technological applications. [ABSTRACT FROM AUTHOR]

Cassava starch solid biopolymer electrolyte (SBPE) films were prepared by a thermochemical method with different concentrations of lithium triflate (LiTFT) as a dopant salt. The process began with dispersing cassava starch in water, followed by heating to facilitate gelatinization; subsequently, plasticizers and LiTFT were added at differing concentrations. The infrared spectroscopy analysis (FTIR-ATR) showed variations in the wavenumber of some characteristic bands of starch, thus evidencing the interaction between the LiTFT salt and biopolymeric matrix. The short-range crystallinity index, determined by the ratio of COH to COC bands, exhibited the highest crystallinity in the salt-free SBPEs and the lowest in the SBPEs with a concentration ratio (Xm) of 0.17. The thermogravimetric analysis demonstrated that the salt addition increased the dehydration process temperature by 5 °C. Additionally, the thermal decomposition processes were shown at lower temperatures after the addition of the LiTFT salt into the SBPEs. The differential scanning calorimetry showed that the addition of the salt affected the endothermic process related to the degradation of the packing of the starch molecules, which occurred at 70 °C in the salt-free SBPEs and at lower temperatures (2 or 3 °C less) in the films that contained the LiTFT salt at different concentrations. The cyclic voltammetry analysis of the SBPE films identified the redox processes of the glucose units in all the samples, with observed differences in peak potentials (Ep) and peak currents (Ip) across various salt concentrations. Electrochemical impedance spectroscopy was used to establish the equivalent circuit model Rf–(Cdl/(Rct–(CPE/Rre))) and determine the electrochemical parameters, revealing a higher conduction value of 2.72 × 10−3 S cm−1 for the SBPEs with Xm = 17 and a lower conduction of 5.80 × 10−4 S cm−1 in the salt-free SBPEs. It was concluded that the concentration of LiTFT salt in the cassava starch SBPE films influences their morphology and slightly reduces their thermal stability. Furthermore, the electrochemical behavior is affected in terms of variations in the redox potentials of the glucose units of the biopolymer and in their ionic conductivity. [ABSTRACT FROM AUTHOR]

Nanocomposites of poly(lactic acid) with sepiolite needles (5 wt.%) were evaluated in terms of the mechanical and biofilm formation properties. The nanocomposite exhibited higher values of the Young's modulus and tensile strength at break compared to the PLA, without detriment in the percent elongation at break. These improvements were related to the high aspect ratio of the nanoclay, the polymer-clay interactions, and the degree of dispersion. The growth of Pseudomonas aeruginosa on the surface of the PLA and nPLA materials was promoted in different conditions. Medium with different concentration of nutrients were used and also were compared the effect of the medium physical state (solid or liquid medium). Biofilms were formed in all the conditions. However, the nanocomposite presented a higher area coverage of microorganisms on its surface, possibly due to the positive effects of the nanoclay on the bacterial adhesion. [ABSTRACT FROM AUTHOR]

Background: Composite materials make it possible to modulate the properties of the source materials and expand their technological potential. In this sense, composite materials made from solid biopolymeric electrolytes and graphene oxide can be an attractive alternative for applications in organic electronics due to their electrochemical properties. Aim: The present work aims to evaluate the electrochemical behavior of a composite material made of solid biopolymeric electrolyte of cassava starch and graphene oxide at different concentrations to determine the effect of this concentration and the pH used in the production process. Methods: The composite material was made from the use of cassava starch plasticized with glycerol, glutaraldehyde, polyethylene glycol and with lithium perchlorate as electrolytes. During the synthesis process, graphene oxide was added in different concentrations (0, 0.25, 0.50, 1.00, 1.25, 1.50, and 1.75 %w/w) to evaluate the effect of the concentration of this component. The synthesis was carried out by thermochemical method with constant heating in an oven at 75 ° C for 48 hours. Films were prepared using synthesis solutions at different pH (5.0 and 9.0). The pH was regulated by adding HCl or NaOH to the synthesis solution as appropriate. Results and Discussion: The results showed that the cassava starch biopolymeric solid electrolyte films without plasticizers were stiff and brittle, so they broke easily. The films with plasticizers and the films of the composite material were stable to the manual traction, allowing their easy manipulation without breaking. The films presented a similar electrochemical behavior in terms of oxide reduction processes; however, the films with graphene oxide presented signals with higher peak currents. Films made at pH 9.0 showed 50 % more intensity in peak currents. The addition of graphene oxide affected the current parameters and peak potentials, being more marked in the films prepared at pH 9.0; at this pH the films with concentrations of graphene oxide lower than 1.00 %w/w presented variable Ep and Ip, while at concentrations of graphene oxide greater than 1%w/w, the behavior did not show significant variations. Conclusions: The addition of graphene oxide modulates or modifies the electrochemical behavior of cassava starch biopolymeric solid electrolyte films, and the processing pH can vary the effect of the graphene oxide addition. [ABSTRACT FROM AUTHOR]

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Background. Coffee samples adulterated with roasted corn and roasted soybean were analyzed using a voltammetric electronic tongue equipped with a polypyrrole sensor array. Materials and methods. Coffee samples were adulterated in concentrations of 2%, 5%, 10% and 20% of roasted corn and roasted soybean; 5 replicates of each were used. The discrimination capacity of a voltammetric electronic tongue elaborated with a polypyrrole sensor array, was evaluated by principal component analysis and cluster analysis, while the capacity to perform quantitative determinations was carried out by partial least squares. Results. The results obtained by the application of principal component analysis showed an excellent ability to discriminate adulterated samples. Additionally, the classifications obtained by cluster analysis was concordant with those obtained by principal component analysis. On the other hand, the evaluation of the ability to quantitatively analyze the adulterated samples showed that the polypyrrole sensor array provides sufficient information to allow quantitative determinations by partial least squares regression. Conclusion. It could be concluded that the voltammetric electronic tongue used in this work allows the sufficient analysis of coffee samples adulterated with roasted corn and roasted soybean. [ABSTRACT FROM AUTHOR]

The development of a multi-channel system is described for electrochemical measurements as part of an electronic tongue fabricated using Programmable System on Chip (PSoC) technology. The purpose of this development is to offer the dairy sector a portable device that can perform the analysis of milk in situ. To obtain signals from a liquid substance, the acquisition circuitry acquires the signal using a variety of sensors, followed by the application of a technique known as cyclic voltammetry, which provides a characteristic pattern for each substance. During the testing, the system uses multivariate statistical methods to clearly differentiate between the characteristics of three types of milk, i.e. whole milk, semi-skimmed milk and lactose-free semi-skimmed milk. [ABSTRACT FROM AUTHOR]