The mechanism of the influence of crystal inhomogeneities on the magnetic and domain microstructures of functional materials based on yttrium iron garnet heterostructures is an important subject of ...investigation due to the aim to predict parameters for manufacturingpurposes. A study of the structural and magnetic characteristics of a set of yttrium iron garnet films grown on gadolinium–gallium garnet substrate is presented. High-resolution X-ray diffractometry, Mössbauer spectroscopy, MFM, as well as ion implantation simulation and X-ray diffraction simulation were used together to determine the features of the effect of Ne+ ion implantation with different dose rates on the samples. The simulation of ion implantation with E = 82 keV showed energy loss profiles of Ne ions with subsequent defect formation up to amorphization of near-surface layers at high doses. Implantation creates two magnetically non-equivalent types of tetrahedrally located Fe3+ ions, which leads to a rotation of the total magnetic moment relative to the film surface and a change in the width of the magnetic domain stripes.
The photocatalytic activity of four titanium dioxide samples (TiO2-P25 Degussa, PC105 Millennium, PC500 Millennium, and Anatase) was studied in the degradation of dyes (Congo Red (CR), Methyl Orange ...(MO), and Direct Red 23 (DR23)) using cost-effective smartphone-based analysis. The obtained kinetic curves are well described by the first-order kinetic model. It was established that the phase composition, the size of the particles, and the specific surface area of the catalyst have a significant effect on the photocatalytic activity of the studied TiO2 samples. It was investigated that the Millennium PC500 sample is the most effective photocatalyst due to a large specific surface area and a small particle size (8 nm). TiO2-P25 Degussa and Anatase also demonstrate a high photocatalytic activity in the degradation of CR and DR23 dyes, which can be explained by the accelerated process of electron transfer between the anatase and rutile phases. For the PC105 sample, a higher CR photodegradation efficiency is observed compared to PC500. It can be concluded that heterogeneous photocatalysis is an effective method for the removal of toxic dyes from wastewater. With the use of smartphone-based analysis, it is possible monitoring the photodegradation kinetics in real-time.
Mn-substituted magnetite samples Fe3-xMnxO4 (x = 0.0; 0.02; 0.05; 0.1; 0.15; 0.2; 0.25) were synthesized using the co-precipitation method. X-ray diffraction patterns confirmed the formation of pure, ...well-crystallized manganese ferrite with a cubic spinel structure. The crystallites size increases sharply for the minimum degrees of substitution, with a subsequent tendency to decrease with the growth of manganese ions content. The catalytic properties of Fe3-xMnxO4 were investigated for the degradation of oxytetracycline (ОТС) and inactivate E. coli. There is a correlation between particle size and catalytic activity. The Fe2.95Mn0.05O4 sample exhibited the highest catalytic activity in the destruction of OTC. The effect of electromagnetic heating (EMH) on the catalytic properties of iron oxides were investigated. The Fe2.9Mn0.1O4 sample with electromagnetic heating achieved 100 % efficiency in decomposing 5 mg/L of OTC. Fe3-xMnxO4 samples reduce the number of Gram-negative bacteria E. coli at concentrations of 104 and 106 CFU/mL. Electromagnetic heating experiments demonstrated high performance, achieving inactivation of 6 logs of E. coli in the presence of Fe2.98Mn0.02O4 and Fe2.95Mn0.05O4 catalysts within 135 minutes. Studies on ecotoxicity have shown that Daphnia magna is a sensitive bioindicator of residual H2O2 concentration. An increase in the Mn2+ content in the synthesized catalysts resulted in a decrease in the toxicity of purified water. The study suggests that Mn-substituted magnetite catalysts are effective materials for catalytic decomposition of OTC and inactivation of E. coli bacteria.
A systematic study of the influence of synthesis conditions on the structural, morphological, and electrical properties, as well as the electrochemical performance of hemp fiber-derived carbon ...materials was performed. An analysis of the capacitive response of carbons obtained under various activation conditions with additional treatment with HNO3 and annealing was completed. The contribution of the formation of an electrical double layer at the outer electrode–electrolyte interface, as well as on surfaces inside micropores, has been studied and analyzed in terms of the effect of the turbostratic carbon properties (average lateral size of graphite crystallites, pore size distribution, BET surface area).
A simple activation method has been used to obtain porous carbon material from walnut shells. The effect of the activation duration at 400 °C in an atmosphere with limited air access on the ...structural, morphological, and electrochemical properties of the porous carbon material obtained from walnut shells has been studied. Moreover, the structure and morphology of the original and activated carbon samples have been characterized by SAXS, low-temperature adsorption porosimetry, SEM, and Raman spectroscopy. Therefore, the results indicate that increasing the duration of activation at a constant temperature results in a reduction in the thickness values of interplanar spacing (d002) in a range of 0.38–0.36 nm and lateral dimensions of the graphite crystallite from 3.79 to 2.52 nm. It has been demonstrated that thermal activation allows for an approximate doubling of the specific SBET surface area of the original carbon material and contributes to the development of its mesoporous structure, with a relative mesopore content of approximately 75–78% and an average pore diameter of about 5 nm. The fractal dimension of the obtained carbon materials was calculated using the Frenkel–Halsey–Hill method; it shows that its values for thermally activated samples (2.52, 2.69) are significantly higher than for the original sample (2.17). Thus, the porous carbon materials obtained were used to fabricate electrodes for electrochemical capacitors. Electrochemical investigations of these cells in a 6 M KOH aqueous electrolyte were conducted by cyclic voltammetry, galvanostatic charge/discharge, and impedance spectroscopy. Consequently, it was established that the carbon material activated at 400 °C for 2 h exhibits a specific capacity of approximately 110–130 F/g at a discharge current density ranging from 4 to 100 mA/g.
The present work reports the results of a systematic study on the evolution of the morphological properties of porous carbons derived from coffee waste using a one-pot potassium-hydroxide-assisted ...process at temperatures in the range of 400–900 °C. Raw materials and obtained carbons were studied by TG, DTG, SEM and nitrogen adsorption porosimetry. The decomposition temperature ranges for hemicellulose, cellulose and lignin as the main component of the feedstock have been established. It is shown that the proposed method for the thermochemical treatment of coffee waste makes it possible to obtain activated carbon with a controllable pore size distribution and a high specific surface area (up to 1050 m2/g). A comparative study of the evolution of the distribution of pore size, pore area and pore volume has been carried out based on the BJH and NL-DFT (slit-like pores approximation) methods. The fractal dimension of the obtained carbons has been calculated by Frenkel–Halsey–Hill method for single-layer and multilayer adsorptions.
The phenomenological model of sulphate anions effect on the nanodispersed titania synthesis during hydrolysis of titanium tetrachloride was studied. It was proposed that both chelating and bridging ...bidentate complexes formation between sulphate anions and octahedrally coordinated Ti(OH)
h
(OH
2
)
6−h
(4−h)+
mononers is the determinative factor for anatase phase nucleation.
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