Post-Fire Mechanical Properties of Concrete Reinforced with Spanish Broom Fibers

In this study, we conducted an initial investigation of the post-fire mechanical properties of concrete reinforced with Spanish broom fibers. The mechanical properties were determined at room temperature, and the post-fire mechanical properties were determined at elevated temperature, so that the fire resistance of the concrete could be determined. Five mixtures were considered: three with differently treated Spanish broom fibers, a polypropylene fiber mixture, and a reference concrete mixture. The concrete and reinforced concrete samples were first dried to 100 °C, then heated to 400 °C, and left to cool to room temperature. The samples were tested immediately and 96 h after cooling. The compressive strength, weight loss, ultrasonic pulse velocity, and dynamic modulus of elasticity were determined and compared. The cross-sectional images of the concrete samples captured through an optical microscope were observed and analyzed. The changes in fiber structure were monitored by TG/DTG analysis. The results of the study indicate that even the reference concrete mixture did not have satisfactory residual properties. The reinforced concretes did not improve the residual properties of the reference concrete, but reduced the spalling and explosive failure performance under a compressive load. The concrete reinforced with Spanish broom fibers showed improved residual properties compared with concrete reinforced with polypropylene fibers

Ultrazvučno potpomognuta kristalizacija magnezijeva hidroksida iz morske vode

High purity magnesium hydroxide has been synthesised from seawater with the addition of dolomite lime as reagent. High intensity ultrasound-assisted crystallization of magnesium hydroxide was carried out during precipitation with the intention to obtain fine particles of Mg(OH)2 as well as to prevent their agglomeration. Investigations were conducted on magnesium hydroxide samples in the form of sludge and voluminous powder. The composition, morphology, and properties of the product were determined by chemical, XRD, FTIR, and SEM/EDS analysis. The particle size distribution was detected by the laser light scattering method. The results showed that the mean particle size of magnesium hydroxide sludge was 5.75 µm, while voluminous powder was 7.58 µm. The morphology of magnesium hydroxide voluminous powder was in the form of aggregated filamentous (up to 300 nm in size) or flake structures. This work is licensed under a Creative Commons Attribution 4.0 International License.Magnezijev hidroksid visoke čistoće sintetiziran je iz morske vode uz dodatak dolomitnog vapna. Ultrazvukom visokog intenziteta potpomognuta kristalizacija magnezijeva hidroksida tijekom precipitacije odvijala se u svrhu dobivanja što finijih čestica Mg(OH)2 i sprječavanja njihove aglomeracije. Ispitivanja su provedena na uzorcima magnezijeva hidroksida u obliku mulja i voluminoznog praha. Sastav, morfologija i svojstva dobivenog produkta analizirani su kemijskom, XRD, FTIR i SEM/EDS analizom. Raspodjela veličine čestica određena je metodom raspršenja laserskog svjetla. Rezultati ukazuju na to da je srednja veličina čestica magnezijeva hidroksida u obliku mulja 5,75 µm, dok je u voluminoznom prahu 7,58 µm. Morfologija voluminoznog praha magnezijeva hidroksida je u obliku aglomeriranih nitastih (duljine do 300 nm) i ljuspičastih struktura. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna

Optimization of Giant Unilamellar Vesicle Electroformation for Phosphatidylcholine/Sphingomyelin/Cholesterol Ternary Mixtures

Artificial vesicles are important tools in membrane research because they enable studying membrane properties in controlled conditions. Giant unilamellar vesicles (GUVs) are specially interesting due to their similarity in size to eukaryotic cells. We focus on optimization of GUV production from phosphatidylcholine/sphingomyelin/cholesterol mixtures using the electroformation method. This mixture has been extensively researched lately due to its relevance for the formation of lipid rafts. We measured the effect of voltage, frequency, lipid film thickness, and cholesterol (Chol) concentration on electroformation successfulness using spin-coating for reproducible lipid film deposition. Special attention is given to the effect of Chol concentrations above the phospholipid bilayer saturation threshold. Such high concentrations are of interest to groups studying the role of Chol in the fiber cell plasma membranes of the eye lens or development of atherosclerosis. Utilizing atomic force and fluorescence microscopy, we found the optimal lipid film thickness to be around 30 nm, and the best frequency–voltage combinations in the range of 2–6 V and 10–100 Hz. Increasing the Chol content, we observed a decrease in GUV yield and size. However, the effect was much less pronounced when the optimal lipid film thickness was used. The results underline the need for simultaneous optimization of both electrical parameters and thickness in order to produce high-quality GUVs for experimental research

Electrocoagulation treatment of compost leachate using aluminium alloy, carbon steel and zinc anode

Analysis of surface changes and corrosion occurrence at the electrode surface, electro-generated sludge analysis, and electrocoagulation (EC) treatment efficiency using aluminium alloy, low carbon steel, and zinc sacrificial anode as electrodes for the treatment of compost leachate with the medium organic load were compared for the first time. Different operating conditions (initial pH values in the range of 4–8, stirring rates in the range 70–270 rpm, and contact times in the range of 10–30 min) were used to study the EC process. Light microscopy analysis show the significant corrosion of anodes, while minor corrosion damage was also observed on the cathodes. Pitting was found on carbon steel and aluminium electrodes, and general corrosion on the zinc electrodes, which increase with the duration of EC (10 to 30 min). Weight loss analysis of electrodes shows a decrease in anode mass in all experiments and aluminium cathode mass, while steel cathode mass increases. Zinc cathode mass increases in initially acid and decreases in an alkaline environment. The highest anode consumption was obtained in the experiment with the Zn electrode (in the range of 0.3300–0.6469 g). SEM/EDS analysis of the electro-generated sludge confirmed the presence of aluminium, zinc, and iron, with oxygen as the main elements, while carbon indicated collected organic matter from the compost leachate. PXRD analysis of sludge shows a mixture of amorphous phase with the a semicrystalline phase of AlO(OH) and the crystalline phase of AlPO4 obtained with Al electrodes, an amorphous structure of the sludge obtained with Fe electrodes, and structurally well-ordered phases of Zn7Cu(OH)13((SiO(OH)3)0.7(O4H7)0.3(SO4)) and (Zn0.9Cu0.1)O obtained with Zn electrodes. In addition, the treatment efficiency was analysed and Taguchi's L9 orthogonal array design was performed

Electrocoagulation Combined with Synthetic Zeolite—Does the Size of Zeolite Particles Matter?

Although electrocoagulation combined with zeolite (ECZ) shows higher efficiency in wastewater treatment, the actual contribution of zeolite particle size has not been fully explored. In this work, the influence of particle size of synthetic zeolite SZ (2), and contact times (10, 20 and 30 min). The results positively highlight that the largest particle size should be used in ECZ, as it leads to a lower increase in pH and temperature, a higher decrease of chemical oxygen demand (COD) and turbidity, and a lower electrode consumption, while causing more damage to the electrode surface. The estimated energy costs ranged from 3.960 kW/m3–1313.657 kW/m3. The Taguchi L9 orthogonal configuration showed the highest COD and turbidity decrease under the conditions of 160–600 µm zeolite particles. The powder X-ray diffractometer (PXRD) analysis shows that interplanar spacing decreases when smaller and medium SZ particle sizes are used, while this effect was not observed with larger zeolite particle size. SEM-EDS shows that oxygen, silicon, and aluminium are the predominant elements in electrogenerated sludge coupled with zeolite

Synchrotron X-ray investigation of the layer spacing in a series of low molar mass bi-mesogen organosiloxane smectic materials.

The temperature dependence of the layer spacing of a series of chiral bi-mesogen organosiloxane liquid-crystal materials is presented. The detailed measurements were taken at the ELETTRA radiation source in Trieste on thin specimens contained between glass coverslips. In the materials with 10 and 11 spacers between the siloxane and the mesogenic moiety, it is observed that the temperature dependence of the layer spacing is not monotonous. In the material with six spacers, there is an abrupt change of 0.01 nm in the layer spacing between 35 °C and 36 °C. In this temperature range, domains with both layer spacing coexist. This observation is in agreement with polarised light microscopy observations; however, detailed differential scanning calorimetry (DSC) measurements show no heat associated with this transition