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A ferroelectric material (Bi0.5Na0.5)0.935Ba0.065TiO3 (BNBT) with a perovskite structure was poled and characterized by electrical impedance spectroscopy as a function of temperature, X-ray diffrac...

In recent years, polymer engineering, at the molecular level, has proven to be an effective strategy to modulate thermal conductivity. Polymers have great applicability in the food packaging industry, in which transparency, lightness, flexibility, and biodegradability are highly desirable characteristics. In this work, a possible manner to adjust the thermal conductivity in cassava starch biopolymer films is presented. Our approach is based on modifying the starch molecular structure through the addition of borax, which has been previously used as an intermolecular bond reinforcer. We found that the thermal conductivity increases linearly with borax content. This effect is related to the crosslinking effect that allows the principal biopolymer chains to be brought closer together, generating an improved interconnected network favoring heat transfer. The highest value of the thermal conductivity is reached at a volume fraction of 1.40% of borax added. Our analyses indicate that the heat transport improves as borax concentration increases, while for borax volume fractions above 1.40%, heat carriers scattering phenomena induce a decrement in thermal conductivity. Additionally, to obtain a deeper understanding of our results, structural, optical, and mechanical characterizations were also performed.

The use of lignocellulosic biomass to produce commercial high-value products has taken force in recent years. Aromatic plants are key raw materials to obtain bioactive compounds with high added value, such as phenolic compounds, but its extraction produces a high amount of wastes. In this sense, the present work aimed to evaluate experimentally the extraction of phenolic compounds from thyme and subsequently, the production of biogas from the remaining of the extraction. To evaluate the prefeasibility of the processes, the simulations of the stand-alone (conventional extraction), as well as the biorefinery (phenolic compounds extraction, biogas production, and a cogeneration system), were carried out and evaluated according to technical, economic, and environmental approaches. The bioactive compound extraction yield was 11.95\\% (w/w) and the methane yield was 114 ml/g volatile solids. In the present work, it was suggested that the stand-alone process becomes to be profitable from a small scale (23 T/day) in comparison with the biorefinery approach, which needs to be worked on a major scale (61 T/day) to be economically feasible. The comparison of the environmental impact generated by each scheme shows the major impact for the biorefinery case., The authors thank “Fondo de Ciencia, Tecnología e Innovación del Sistema General de Regalías, Fondo Nacional de Financiamiento para la Ciencia, la Tecnología y la Innovación Francisco José de Caldas, Ministerio de Ciencia, Tecnología e Innovación-MINCIENCIAS, Programa Colombia BIO, Gobernación de Boyacá”, through FP44842-298-2018 contract, Office of the Vice President for Research, Science and Technology-University of Boyacá for the financial support., info:eu-repo/semantics/publishedVersion

A sugar solution measurement system was developed based on the dielectric properties of the sucrose molecule. An ac conductivity and tan &delta, study as a function of the frequency was performed to find the suitable frequency range for the measuring system. The results indicate that it is possible to obtain a better response of the sensor using the frequencies as the maxima peak in tan &delta, appears. Developed setup for sucrose solution was appropriate to measure in a 0.15 to 1 g/mL range with an experimental error of about 3%. The proposed system improves the measurement time over some other methods.

Este trabajo describe la síntesis y caracterización de dos hidróxidos dobles laminares Mg2Al-NO3 sintetizados mediante el método de coprecipitación. El comportamiento eléctrico delos materiales fue evaluado por espectroscopía dieléctrica. Los resultados del análisis dedifracción de rayos X mostraron la formación de una estructura laminar; la presencia de todaslas especies en la estructura del material sintetizado se confirmó por absorción atómica yespectroscopía de infrarrojo. Por microscopía electrónica de transmisión se observó agregadosde partículas en forma de placas. Los resultados de espectroscopía dieléctrica obtenidosa temperatura ambiente muestran un comportamiento de polarización de orientación quesugiere la rotación de moléculas de agua a alta frecuencia y la rotación de aniones nitratoen el espacio interlaminar a baja frecuencia que puede ser responsable de la conductividadiónica observada en el material. This work describes the synthesis and characterization of Mg2Al-NO3 layered doublehydroxides nanomaterial prepared using a coprecipitation method. The electrical behavior ofthis material was evaluated using dielectric spectroscopy. The results from X-ray diffractionanalysis showed the formation of lamellar structure, while the atomic absorption and infraredspectroscopy confirms the presence of all species inthe structure of the synthesized material.TEM shows clusters of plate-like particles and the dielectric spectroscopy results at roomtemperature show an orientational polarization behavior that suggests the rotation of watermolecules at high frequency. TEM results also demonstrate the rotation of nitrate anions inthe interlayer spacing at low frequency, which may be responsible for producing anionicconductivity.

Alumina-supported manganese catalysts with cryptomelane and/or birnessite structure have been prepared using a simple method based on the thermal decomposition of potassium permanganate. The samples have been characterized by XRD, FTIR, TGA, DSC, N2 adsorption at −196 °C, SEM, H2-TPR and XPS, and their catalytic activity for soot combustion has been tested and compared to that of a reference Pt/alumina catalyst. The thermal decomposition of alumina-supported KMnO4 yields a mixture of supported birnessite and potassium manganate which is the most effective, among those prepared, to lower the soot combustion temperature. However, this material is not useful for soot combustion because the accelerating effect is not based on a catalytic process but on the oxidation of soot by potassium manganate. A suitable soot combustion catalyst is obtained after potassium manganate is removed by water washing, yielding only the birnessite phase on the γ-Al2O3 support. This birnessite phase can be transformed into cryptomelane by calcination at 600 °C. These two samples, γ-Al2O3-supported birnessite and cryptomelane are suitable catalysts for soot combustion in NOx/O2 mixtures, as their catalytic activity is based on the NO2-assited mechanism, that is, both catalysts accelerate the oxidation of NO to NO2 and NO2 promotes soot oxidation. The soot combustion temperatures obtained with these birnessite/cryptomelane alumina-supported catalysts are similar to that obtained with the reference Pt/alumina catalyst. The authors thank to Spanish government (MICINN project CTQ2009-07475), DIMA (Dirección de Investigaciones) and Laboratorio de Magnetismo y Materiales Avanzados (Universidad Nacional de Colombia, Sede Manizales) and Vicerrectoría de Investigaciones de la Universidad de Caldas for the financial support.