Drying parameters influence on ‘Ameclyae’ Opuntia ficus prickly pear oil quality

[EN] The aim of this work is to study the effects of drying conditions on the quality of extracted pricly pear seed oil, specifically α-tocopherol content. Drying experiments were carried on following a full 23 factorial design using a vertical drying tunnel. The temperature range was 45 to 70°C, relative humidity range was 15 - 30% and air velocity was 1 and 2 m/s. The Midilli-Kucuk model was found with satisfaction describing the seed air drying curves with a correlation coefficient of 0.999 and a standard error of 0.01. For each drying condition, the extraction of fixed oil seeds was performed at cold using mechanical pressing method. The oil quality was evaluated on the basis of the a-tocopherol content. The a-tocopherol was identified and quantified by high-performance liquid chromatography (HPLC-UV). According to the experimental results, it was found that convective drying of thin layer of seeds at soft air conditions, drying temperature of 45°C, relative humidity of 15% and air velocity of 1m/s give the optimal quality of extracted oil in terms of a-tocopherol content.Hassini, L.; Desmorieux, H. (2018). Drying parameters influence on ‘Ameclyae’ Opuntia ficus prickly pear oil quality. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 115-122. https://doi.org/10.4995/IDS2018.2018.7861OCS11512

Ab initio study of magnetism at the TiO2/LaAlO3 interface

In this paper we study the possible relation between the electronic and magnetic structure of the TiO2/LaAlO3 interface and the unexpected magnetism found in undoped TiO2 films grown on LaAlO$_3$. We concentrate on the role played by structural relaxation and interfacial oxygen vacancies. LaAlO3 has a layered structure along the (001) direction with alternating LaO and AlO2 planes, with nominal charges of +1 and -1, respectively. As a consequence of that, an oxygen deficient TiO2 film with anatase structure will grow preferently on the AlO2 surface layer. We have therefore performed ab-initio calculations for superlattices with TiO2/AlO2 interfaces with interfacial oxygen vacancies. Our main results are that vacancies lead to a change in the valence state of neighbour Ti atoms but not necessarily to a magnetic solution and that the appearance of magnetism depends also on structural details, such as second neighbor positions. These results are obtained using both the LSDA and LSDA+U approximations.Comment: Accepted for publication in Journal of Materials Scienc

Correlations of structural, magnetic, and dielectric properties of undoped and doped CaCu3Ti4O12

The present work reports synthesis, as well as a detailed and careful characterization of structural, magnetic, and dielectric properties of differently tempered undoped and doped CaCu3Ti4O12 (CCTO) ceramics. For this purpose, neutron and x-ray powder diffraction, SQUID measurements, and dielectric spectroscopy have been performed. Mn-, Fe-, and Ni-doped CCTO ceramics were investigated in great detail to document the influence of low-level doping with 3d metals on the antiferromagnetic structure and dielectric properties. In the light of possible magnetoelectric coupling in these doped ceramics, the dielectric measurements were also carried out in external magnetic fields up to 7 T, showing a minor but significant dependence of the dielectric constant on the applied magnetic field. Undoped CCTO is well-known for its colossal dielectric constant in a broad frequency and temperature range. With the present extended characterization of doped as well as undoped CCTO, we want to address the question why doping with only 1% Mn or 0.5% Fe decreases the room-temperature dielectric constant of CCTO by a factor of ~100 with a concomitant reduction of the conductivity, whereas 0.5% Ni doping changes the dielectric properties only slightly. In addition, diffraction experiments and magnetic investigations were undertaken to check for possible correlations of the magnitude of the colossal dielectric constants with structural details or with magnetic properties like the magnetic ordering, the Curie-Weiss temperatures, or the paramagnetic moment. It is revealed, that while the magnetic ordering temperature and the effective moment of all investigated CCTO ceramics are rather similar, there is a dramatic influence of doping and tempering time on the Curie-Weiss constant.Comment: 10 pages, 11 figure

Elaboration and characterization of clay-sand composite based on Juncus acutus fibers

International audienceThe study reported in this paper was undertaken to investigate the feasibility of lightweight construction materials, based on vegetable fibres. This innovative material consisted of mixture of natural clay (60%) and natural sand (40%) reinforced with different levels of fibers extracted from Jancus acutus ``Smar''. The fibers were used as partial replacement of sand in mixture by volume at: 0% (Control Specimen), 5%, 10%, and 20%. The objective of this work is to evaluate the physico-mechanical properties, through the examination of materials lightning, mechanical strengths (compressive and flexural). Due to the high hygroscopic nature of the vegetable fibers, the thermal conductivity of the composite materials was measured at both wet and dry state at different volumes of Juncus fibers replacement. Test-results have shown that the addition of 20% fibers decreased the composite bulk density from 1900 kg/m(3) to 1100 kg/m(3), which results in a high reduction of mechanical performances in terms of compressive and flexural strengths. The experimental investigation of thermal behaviour of this composite has shown that the increase of fibers volume leads to a significant decrease in thermal conductivity. For a composite containing 20% of fibers replacement, the dry thermal conductivity decreased from 0.902 W/m.K for control specimen (without fibers) to a value of 0.327 W/m.K. However, at wet state, the corresponding thermal conductivity decreased from 1.543 W/m.K to 0.361 W/m.K. Despite the decrease in mechanical strengths, the resulting composite can thus be considered as a promising candidate for use in thermal insulation material, because a conductivity of 0.350 W/m.K is generally considered as the worst acceptable value for insulating building material. (C) 2019 Elsevier Ltd. All rights reserved