Study of an Ecological Cement-Based Composite with a Sustainable Raw Material, Sunflower Stalk Ash

The use of plant ash as a sustainable cementitious material in concrete composition is a widely researched subject in the construction domain. A plant studied so far more for its thermal insulation properties, sunflower, was analyzed in this study with regard to its ash effects on the concrete composition. The present research aimed to analyze the effects of a 2.5%, 5%, 7.5%, 10%, 15%, 20%, or 30% volume replacement of cement by sunflower stalk ash (SA), a sustainable cementitious material, on the concrete compressive strength at 28 days and three months, the flexural and splitting tensile strengths, the resistance to repeated freeze–thaw cycles, and the resistance to chemical attack of hydrochloric acid. The elementary chemical composition of the SA and the composites was included also. According to the experimental results, SA decreased the values of the compressive and tensile strength of the concrete, but it improved the concrete behavior under repeated freeze–thaw cycles and under the action of hydrochloric acid. A percent of 10% of SA led to a much more pronounced development of compressive strength over time than conventional concrete (26.6% versus 12%).

Erscheinung, Erscheinen (Manifestation)

The lexeme Erscheinung/Erscheinen (manifestation) is related to the formative process of Werden (becoming) that fascinated Goethe throughout his life and which, in turn, is part and parcel of his understanding of morphology in all its manifestations, from the most elementary chemical processes to the highest products of the human mind. Because he was convinced that every existent thing necessitates interpretation to be grasped in its changefulness, he employed a range of surrogates to express the meanings of Erscheinung/Erscheinen. Thus, the lexeme can be translated in different ways: foremost as manifestation, phenomenon, appearance, or illusion. Moreover, Goethe believed that each manifestation is the result of an unrecognized law in the appearing object that corresponds to an unknown regulating principle in the observing subject and that nothing in living nature is static or occurs in isolation; everything is interconnected. Thus, Goethe’s method of inquiry consisted of close empirical observation that included reflection on the observing subjects themselves—a form of phenomenology. Consequently, Anschauen and Gegenstand also enter into the semantic field. Finally, the following examination highlights a lesser-known signification of Erscheinung in Goethe’s usage, one for which he did not have a specific term: that of emergence. Emergence seems most apt to express Goethe’s “lebendiger Begriff” (living concept), which can be seen as the counterpart to nature’s “lebendiges Fließen” (living flow), which he repeatedly expressed in his literary and scientific writing.

n the Validity of Minimum Magnetizability Principle in Chemical Reactions

A new principle known as Minimum Magnetizability Principle has recently been introduced in the context of Density Functional Theory. In order to validate this principle, changes in the magnetizability (Δξ) and its cube-root (Δξ1/3) are computed at B3LYP/LanL2DZ level of theory for some elementary chemical reactions. The principle is found to be valid for 77% of reactions under study. It is observed that the molecules with the lowest sum of ξ or ξ1/3 are generally the most stable. The principle fails to work in the presence of hard species. A comparative study is also made with change in hardness (Δη), electrophilicity index (Δω), polarizability (Δα) and their cube-roots (Δη1/3, Δω1/3, Δα1/3). It is observed that the Minimum Magnetizability Principle is nearly as reliable as Minimum Electrophilicity Principle. It appears that this principle could be helpful in predicting the direction of diverse reactions as well as stable geometrical arrangements.

Energetic characterization and radiographic analysis of torrefied coated MDF residues

The use of wood panel residues as biomass for energy production is feasible. Heat treatments can improve energy properties while minimizing the emission of toxic gases due to thermoset polymers used in Medium Density Fiberboard (MDF) panels. Torrefaction or pre-carbonization, a heat treatment between 200 and 300 °C with low oxygen availability accumulates carbon and lignin, decreases hygroscopicity, and increases energy efficiency. The objective of this work was to evaluate the energy parameters (immediate, structural, and elementary chemical composition, moisture content, and yield) and density in torrefied MDF panels. The torrefaction improved the energetic features of coated MDF, decreasing the moisture content, volatile matter, and consequently, concentrating the carbon with better results in the samples torrefied for 40 min. The densitometric profiles of the torrefied MDF, obtained by X-ray densitometry, showed a decrease in the apparent density as torrefaction time increased. The digital X-ray images in gray and rainbow scale enabled the most detailed study of the density variation of MDF residues.

Determining patterns in the use of finishing formulations for trimming the Crust leather

This paper has considered the possibility of using new finishing formulations to finish the Crust leather, manufactured from cattle raw materials aimed to finish shoes and leather garments.The quality indicators of finishing formulations and their elementary chemical composition have been investigated. It was found that the finishing formulations possess a high covering capacity due to the presence of mineral pigments in their composition. X-ray fluorescent analysis has proven that the presence of chromium pigments and copper compounds renders the green color to the composition; the compounds of cobalt, copper, iron, chromium ‒ blue color; cobalt compounds ‒ reddish-brown color.It has been established that the finishing formulations are resistant to the effect of electrolytes of different nature over a wide pH interval, from 2 to 11.When determining the uniformity of the composition by using a chromatography method involving fan-shaped paper, it was found that the composition of blue has a pronounced purple hue, of reddish-brown – red.The effectiveness of the use of finishing formulations to finish the Crust leather has been proven by determining the indicators of its quality. The finishing formulations give the Crust high resistance to dry (exceeding 500 rotations) and wet friction (exceeding 150 rotations), multiple bending (exceeding 50,000 rotations), the effect of water (2 to 5 points), and organic solvents (2 to 4 points). At the same time, the finishing formulations are characterized by rapid diffusion into the structure of the leather with a natural front surface with the simultaneous provision of specific properties to it. Specifically: water-repelling properties (hydrophobicity), shine, wax grain, matte, saturated homogeneous color. The leather with the introduced finishing formulations does not require fixing the resulting coating with water-based varnish.It is recommended to use the finishing formulations in the production of Crust leather shoe top by applying them onto the surface by spraying or using a brush to create the desired effect

Sustainable catalytic rearrangement of terpene-derived epoxides: towards bio-based biscarbonyl monomers

Seeking a sustainable and selective approach for terpene modification, a catalyst deconvolution approach was applied to the Meinwald rearrangement of (+)-limonene oxide as a model substrate to yield dihydrocarvone. In order to identify the most suitable catalyst and reaction conditions, different Lewis acids were evaluated. Bismuth triflate proved to be the most active catalyst under mild reaction conditions, with a low catalyst loading (1 mol%) and a relatively short reaction time (3 h). The optimized reaction conditions were subsequently transferred to other terpene-based epoxides, yielding different bio-based biscarbonyl structures, which constitute interesting and valuable substances, e.g. for polymer synthesis or as fragrances. Monoepoxides derived from ( R )-(−)-carvone and (+)-dihydrocarvone rearranged to the desired products with high selectivities and yields. γ-Terpinene dioxide could be transformed in a double rearrangement to the respective biscarbonyl in moderate yields. A better result was achieved for limonene dioxide after further adjustment of the protocol to reach acceptable yields with a low catalyst loading of 0.1 mol% using 2-methyl tetrahydrofuran as a sustainable solvent. Compared to many procedures described in the literature, this procedure represents a step towards an increased sustainability in terpene modification by considering several principles of Green Chemistry, such as renewable resources, catalysis and mild reaction conditions for elementary chemical transformations. This article is part of a discussion meeting issue ‘Science to enable the circular economy’.