Frost-retted hemp fibers were investigated to assess their suitability for composite applications. Chemical analysis of frost-retted hemp fibers highlighted a high amount of solubles (pectins) at the ...fibers surface and a low lignin content in the fibers that was attributed to an unfavorable synthesis of lignin in the cell wall due to the particularly cold temperature during hemp growth in the Nordic countries. The fibers tensile properties were considered at two different scales and the performances of hemp/PLA composites were assessed. Recommendations were provided for the use of frost-retted hemp fibers in the reinforcement of thermoplastic composites.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
In this study, TiO2 thin films were deposited by ultrasonic spray pyrolysis from solutions with concentrations of 0.1 and 0.2 M. The deposition temperature was adjusted at 350 °C and all samples were ...annealed at 500 °C for 1 h in air. The thickness of TiO2 films was changed in the range of 50 to ca. 800 nm by varying the number of spray cycles from 1 to 21 and the solution concentration. The results showed that the mean crystallite size of the anatase structure, the surface roughness, and light absorption increased with the film thickness. The effect of film thickness on the photocatalytic activity was investigated with the photodegradation of stearic acid under UV-A irradiation. The optimal thickness of TiO2 films fabricated by ultrasonic spray pyrolysis for photocatalytic self-cleaning applications was in the range of 170–230 nm, indicating a ca. 2.6 times-higher photocatalytic self-cleaning activity compared to the reference sample, Pilkington ActivTM. The photocatalytic results showed that the 190 nm-thick TiO2 film deposited from the 0.1 M solution applying seven spray cycles exhibited the finest grain structure and maximum photocatalytic activity, leading to 94% of stearic acid degradation in 180 min under UV-A light with the reaction rate constant k = 0.01648 min−1.
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This article investigates the effects of combining a novel protic ionic liquid-based fire retardant (FR) with alkalized hemp fiber. A pivotal importance of this study refers to the hydrophilic ...properties and limits regarding poor thermal resistance of green composites where standard guidelines for fire risks are crucial. Although it is well-studied that alkalization is essential for green composite’s moisture and mechanical durability, research on the flammability of such a combined treatment for natural fiber-reinforced biopolymer composites is lacking. The alkaline treatment used in the current study follows a process already studied as optimal, particularly for the selected hemp fiber. The fire performance was examined using a bench scale approach based on self and piloted ignition from cone calorimeter tests. The result from the Fourier-transform infrared analysis of the hemp fiber confirms phosphorylation following the fire-retardant treatment, which was visible from the morphological examination with scanning electron microscope. The presence of FR in the composites led to impactful moisture sorption. However, the FR composites demonstrated an enhanced response to fire, indicating potential use as a Class B standard for building construction, and hazard level 3 (HL3) classification as an interior material in vehicles, provided the problem of high emission of smoke is mitigated.
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Novel composite self-disinfecting films of polylactic acid (PLA) filled with nanosized particles of double sodium-copper(II) paratungstate B Na
Cu
(CuOH)
W
O
(OH)
·32H
O (POM) were developed. The ...solvent casting (POM/PLA film) and solvent-free melt extrusion methods (Extr. POM/PLA film) were applied for film preparation. The copper (II) ion release to water from both types of the films after 10 days at different temperatures demonstrated that the PLA matrix acts as a diffusion barrier, and the resulting concentration of released copper in water at room temperature remained low, at 0.79% for POM/PLA film and 0.51% for Extr. POM/PLA film. The POM-containing films reveals a significant inhibitory effect against
ATCC 25922 in the agar diffusion test. The numbers of CFUs in washes of the films after incubation for 24 h were found to be 3.6
CFU mL
(POM/PLA film) and 4.1
CFU mL
(Extr. POM/PLA film). The films combine the antibacterial properties of POM and a bio-based polymer matrix, which makes them a prospective coating material for applications in hospital indoor environments. Excellent thermal stability of POM gives a technological advantage for industrial manufacturing to allow the processing of novel composite material in the solvent free (molten) state.
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Cation substitution in Cu2ZnSn(S,Se)4 offers a path to improved solar cell device performance through the modification of the structural, optical and electrical properties of the absorber material. ...In the present study, the effect of partial substitution of copper with silver in Cu1.85(Zn0.8Cd0.2)1.1SnS4 monograin powders was investigated. (Cu1−xAgx)1.85(Zn0.8Cd0.2)1.1SnS4 (ACZCTS) monograin powders with different ratios of Ag/(Cu + Ag) were synthesized from CuS, Ag2S, ZnS, CdS, SnS and elemental sulfur in the liquid phase of KI as the flux material in evacuated quartz ampoules at 740 °C. EDX analysis of the as-grown materials in the entire series revealed that the Ag concentration was different in the synthesized materials than in the corresponding precursor mixtures. Furthermore, the Ag concentration at the surface of crystals was found to be higher than in the bulk of crystals. By increasing the input Ag content, the shape of grown crystals changed from sharp edged tetragonal to a more rounded form. Raman spectra showed a shift in the A peak position from 336 to 334 cm−1 as the Ag content increased in (Cu1−xAgx)1.85(Zn0.8Cd0.2)1.1SnS4. The changes in the recombination processes were studied by temperature dependent photoluminescence spectroscopy and current–voltage characteristics analysis. It was found that the acceptor concentration in the absorber can be modified by varying the Ag content in ACZCTS. The incorporation of Ag into the Cu1.85(Zn0.8Cd0.2)1.1SnS4 monograin absorber material improved the efficiency of monograin layer solar cells from 6.62% (x = 0) to 8.73% (x = 0.01).
Acetylacetone is used as a chelating agent for titanium(IV) isopropoxide to inhibit hydrolysis and stabilize the precursor solution. The effect of the molar ratio between titanium(IV) isopropoxide ...and acetylacetone of 1:1, 1:2, 1:3 and 1:4 in the precursor solution on the morphological, structural and optical properties of TiO2 thin film was investigated. These properties were studied using Fourier transformed infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, X-ray diffraction and UV–vis spectroscopy as a function of the molar ratios for the as-deposited thin films and films annealed at temperatures of 700, 800 and 950°C. Mixed anatase and rutile phases were detected after annealing at 800°C for 1:1 and 1:2 molar ratios and at 700°C for 1:3 and 1:4 molar ratios. The optical band gap decreased from 3.45 to 3.02eV with an increase in the annealing temperature in agreement with corresponding structural changes.
•The grain sizes of TiO2 thin films could be varied over the range of 20 to 210nm.•TTIP and AcacH ratio affects the transformation process from anatase to rutile.•TiO2 bandgap decreased from 3.45 to 3.02eV with an increase in annealing temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A series of heterogeneous catalysts anchored to different polystyrene-based supports has been prepared and applied in an asymmetric 2,3-Wittig rearrangement reaction of cyclohexanone derivatives. ...Among them, primary amino acid-derived (aminomethylated)polystyrene-supported catalysts showed excellent reactivity leading to the formation of rearranged products in good enantioselectivities of both diastereomers. Reusability issues connected to the deactivation of the catalyst were proved to be dependent on the end-capping strategy chosen for the blocking of the unreacted active sites of the resin. This issue of end-capping has not previously been in focus. Using bulkier pivaloyl end-capping moiety, we were able to recycle the catalyst in six consecutive cycles with only marginal deceleration of the reaction. Moreover, the epimerization of the product that occurred while conducting a rearrangement reaction in the presence of a homogeneous catalyst was almost fully eliminated by switching the catalytic system to heterogeneous.
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•Chiral heterogeneous primary amino acid-derived catalysts were synthesized•Challenges related to the reusability of the catalytic system were resolved•The essential role of end-capping was showed as pivotal for achieving recyclability•Pivaloyl chloride was the most efficient reagent for the end-capping
Organic chemistry
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Chemical spray pyrolysis (CSP) is a fast wet-chemical deposition method in which an aerosol is guided by carrier gas onto a hot substrate where the decomposition of the precursor chemicals occurs. ...The aerosol is produced using an ultrasonic oscillator in a bath of precursor solution and guided by compressed air. The use of the ultrasonic CSP resulted in the growth of homogeneous and well-adhered layers that consist of submicron crystals of single-phase Sb2S3 with a bandgap of 1.6 eV if an abundance of sulfur source is present in the precursor solution (SbCl3/SC(NH2)2 = 1:6) sprayed onto the substrate at 250 °C in air. Solar cells with glass-ITO-TiO2-Sb2S3-P3HT-Au structure and an active area of 1 cm2 had an open circuit voltage of 630 mV, short circuit current density of 5 mA/cm2, a fill factor of 42% and a conversion efficiency of 1.3%. Conversion efficiencies up to 1.9% were obtained from solar cells with smaller areas.
Uuringus käsitletakse kolme erinevat materjali (puhas volfram ja kaks volframisulamit Fe ja Ni lisanditega), mida on kiiritatud 20 vöi 25 ja 100 körgtemperatuurse deuteeriumiplasma pulsiga. Seejärel ...on analüüsitud kahjustatud piirkondade jaotust kiiritatud pindadel ning kahjustamata piirkondade jaotumise omadusi, kasutades selleks multifraktaalanalüüsi. Leiti, et mittekahjustatud pindade jaotuse multifraktaalanalüüsi parameetrite keskväärtused hajuvad vähem kui kahjustuste jaotuse analüüsi tulemused. Selgus kehtiv tendents, et mida heledam on algne sisendpilt, seda täpsemad on tulemused mittekahjustatud pinna uurimisel multifraktaalsete karakteristikute abil.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This study aims to determine the catalytic activity and stability of ligand-modified UiO-66 with different functional groups (−NO2, −OH) in deep oxidative desulfurization from a model fuel (MF). The ...planar sulfur compounds included dibenzothiophene (DBT), 2-methylbenzothiazole (2-MB), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in n-dodecane as the fuel phase. The synthesized functionalized metal–organic framework (MOF) samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), nitrogen adsorption–desorption analysis, and microwave plasma-atomic emission spectrometer (MP-AES). The experiment assessment and desulfurization reaction optimization were carried out by the central composite design methodology. Response surface methodology and analysis of variance were employed to evaluate the individual process factors, their interactions, and sulfur removal responses. The responses showed that the oxidation of the planar compounds declined following the sequence DBT > 2-MB ≫ 4,6-DMDBT for all the MOFs. The findings revealed that at 66.7 °C, 3.0 equiv of oxidative agent over sulfur and 9.7 of MOF over sulfur by weight achieved the highest removal efficiency of 98.68% DBT, 93.23% 2-MB, and 69.32% 4,6-DMDBT for UiO-66-NO2 as a catalyst from the model fuel. It was also observed that UiO-66-NO2 had a higher efficiency in deep oxidative desulfurization when compared to other UiO-66-based catalysts used in the current study. Under optimal conditions, all the MOFs showed acceptable catalytic activity and reusability after four runs, although gradual loss of activity was observed.
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