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Deposition time and annealing effects on morphological and optical properties of ZnS thin films prepared by chemical bath deposition

Abstract

Nanocrystalline zinc sulfide thin films were prepared on glass substrates by chemical bath deposition method using aqueous solutions of zinc chloride, thiourea ammonium hydroxide along with non-toxic complexing agent trisodium citrate in alkaline medium at 80 °C. The effect of deposition time and annealing on the properties of ZnS thin films was investigated by X-ray diffraction, scanning electron microscopy, optical transmittance spectroscopy and four-point probe method. The X-ray diffraction analysis showed that the samples exhibited cubic sphalerite structure with preferential orientation along 〈2 0 0〉 direction. Scanning electron microscopy micrographs revealed uniform surface coverage, UV-Vis (300 nm to 800 nm) spectrophotometric measurements showed transparency of the films (transmittance ranging from 69 % to 81 %), with a direct allowed energy band gap in the range of 3.87 eV to 4.03 eV. After thermal annealing at 500 °C for 120 min, the transmittance increased up to 87 %. Moreover, the electrical conductivity of the deposited films increased with increasing of the deposition time from 0.35 × 10−4 Ω·cm−1 to 2.7 × 10−4 Ω·cm−1.

Open access
Application of novel complexing agent in sorption of heavy metal ions from wastewaters on ion exchangers of various types

Application of novel complexing agent in sorption of heavy metal ions from wastewaters on ion exchangers of various types

Ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) are very effective chelating agents used in many branches of industry. However, they are characterized by low biodegradability (EDTA) and carcinogenic effect (NTA), additionally they are quite persistent in the environment. The search for a cost effective alternative to these two most frequently used chelating agents has long been an industry target. One of them is N, N-bis(carboxylmethyl)-L-glutamic acid whose tetrasodium salt known as Dissolvine GL-38. The aim of our work was to investigate Dissolvine GL-38 as a potential alternative for EDTA or NTA in effective removal of heavy metal ions from waters and wastewaters. In the presented paper there were used for the sorption of of heavy metal ions two commercially available ion exchangers: Lewatit MonoPlus MP 64 and Purolite S-920. A series of experiments was conducted to optimise the method for the Cu(II), Zn(II), Ni(II) and Cd(II) removal from industrial effluents. It was found that the sorption efficiency of the monodisperse polystyrene anion exchanger as well as the chelating ion exchanger varied depending on metal ions concentration, pH, phase contact time, agitation, temperature and properties of ion exchangers.

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TS-BTPhen as a promising hydrophilic complexing agent for selective Am(III) separation by solvent extraction

Abstract

The novel hydrophilic back-extraction agent TS-BTPhen (3,3ʹ,3ʺ,3ʹʺ-[3-(1,10-phenanthroline-2,9-diyl)-1,2,4-triazine-5,5,6,6-tetrayl]tetrabenzenesulfonic acid) was tested for its selectivity towards Am(III) over Cm(III) and Eu(III) with a TODGA (N,N,Nʹ,Nʹ-tetraoctyldiglycolamide) based solvent. Batch experiments were carried out using TS-BTPhen dissolved in aqueous nitric acid solution with tracers of 152Eu, 241Am and 244Cm. A significant increase of the separation factor for Cm over Am from SFCm/Am = 1.6 up to SFCm/Am = 3.3 was observed compared to the use of a TODGA-nitric acid system alone. Furthermore, stripping was possible at high nitric acid concentrations (0.6-0.7 mol/L) resulting in a low sensitivity to acidity changes. The influence of the TS-BTPhen concentration was analyzed. A slope of -2 was expected taking into account literature stoichiometries of the lipophilic analogue CyMe4BTPhen. However, a slope of -1 was found. Batch stripping kinetics showed fast kinetics for the trivalent actinides. As an alternative organic ligand the methylated TODGA derivate Me-TODGA (2-methyl-N,N,Nʹ,Nʹ-tetraoctyldiglycolamide) was tested in combination with the hydrophilic TS-BTPhen. The Am(III) separation was achieved at even higher nitric acid concentrations compared to TODGA.

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Structural, morphological, optical and diode properties of chemical bath deposited nano-structured CdS thin films using EDTA as a complexing agent

Abstract

CdS thin films with (1 1 1) orientation were prepared by chemical bath deposition technique at 80±5 °C using the reaction between NH4OH, CdCl2 and CS(NH2)2. The influence of annealing temperature varying from 150 °C to 250 °C was studied. X-ray diffraction studies revealed that the films are polycrystalline in nature with cubic structure. Various parameters, such as dislocation density, stress and strain, were also evaluated. SEM analysis indicated uniformly distributed nano-structured spherically shaped grains and net like morphology. Optical transmittance study showed the wide transmittance band and absence of absorption in the entire visible region. I-V characterization of p-Si/n-CdS diode and photoluminescence studies were also carried out for the CdS films.

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The impact of a relaxation time on the quality of a pigment layer for a solar collector

Vplyv relaxačného času na kvalitu pigmentovanej vrstvy solárneho kolektora

Skúmal sa vplyv relaxačného času periodického reverzného prúdu na kvalitu vyfarbovania povrchu anodicky oxidovaného hliníka. Na vyfarbovanie sa použil elektrolyt bez komplexotvorného činidla a s komplexotvorným činidlom. Študoval sa aj vplyv frekvencie impulzového prúdu. Kvalita vyfarbených povrchov sa hodnotila spektrokolorimetricky a množstvo vylúčeného niklu sa určilo atómovou absorpčnou spektroskopiou. Zistilo sa, že relaxačný čas periodického reverzného prúdu významne ovplyvňuje kvalitu vyfarbených povlakov pre elektrolyty bez komplexotvorného činidla.

Open access
An agent-oriented hierarchic strategy for solving inverse problems

Abstract

The paper discusses the complex, agent-oriented hierarchic memetic strategy (HMS) dedicated to solving inverse parametric problems. The strategy goes beyond the idea of two-phase global optimization algorithms. The global search performed by a tree of dependent demes is dynamically alternated with local, steepest descent searches. The strategy offers exceptionally low computational costs, mainly because the direct solver accuracy (performed by the hp-adaptive finite element method) is dynamically adjusted for each inverse search step. The computational cost is further decreased by the strategy employed for solution inter-processing and fitness deterioration. The HMS efficiency is compared with the results of a standard evolutionary technique, as well as with the multi-start strategy on benchmarks that exhibit typical inverse problems’ difficulties. Finally, an HMS application to a real-life engineering problem leading to the identification of oil deposits by inverting magnetotelluric measurements is presented. The HMS applicability to the inversion of magnetotelluric data is also mathematically verified.

Open access
Microextraction based on solidified floating organic drop coupled with ETAAS for the determination of lead in herbs

Abstract

A rapid, inexpensive and practical solidified of floating organic droplet microextraction (SFODME) prior to electrothermal atomic absorption spectrometry (ETAAS) was proposed for lead (Pb) determination in herb samples. For SFODME procedure, 1-(2-pysidylazo)-2-naphthol was used as a complexing agent. Analytical parameters influencing the extraction efficiency, i.e. types and volume of extracting solvent, concentration of 1-(2-pyridylazo)-2-naphthol, pH, extraction temperature and time were optimized. Under the optimized conditions, LOD and LOQ were 0.064 and 0.214 μg L−1, respectively, and an enrichment factor was achieved at 18.71 with the relative standard deviation ranging from 1.3 to 2.5% (n=6). The proposed method was effectively applied to the determination of lead in Spinach leaves (SRM-1570a) and Thai herb samples with acceptable results.

Open access
Carbonization of solid uranyl-ascorbate gel as an indirect step of uranium carbide synthesis

Abstract

The studies of the synthesis of uranium carbide from uranyl-ascorbate gels using the complex sol-gel process (CSGP) have been carried out. The synthesis of uranyl-ascorbate mixture as liquid sol from uranium trioxide and ascorbic acid and solid gel by extraction of water from sol were carefully examined. Ascorbic acid was used as a complexing agent in complex sol-gel process and as a carbon source. The crucial step to obtain final uranium carbides from the aforementioned substrates is the carbonization process. The thermal behavior of ascorbic acid and uranyl-ascorbate gels in a nitrogen atmosphere in the temperature range of 25-900°C were investigated using TG-DTG. Furthermore, the products of the carbonization of uranyl-ascorbate gels in nitrogen, argon and vacuum atmosphere were identified by X-ray diffraction. TG-DTG was used also as a method for determining of carbon residues in the samples.

Open access
Kinetic properties and structural analysis of LaCrO3 nanoparticles

Abstract

LaCrO3 perovskite nanopowders were successfully prepared via a sol-gel method using stoichiometric proportion of materials containing lanthanum and chromium in stearic acid complexing agent. Structural analysis of LaCrO3 indicated an octahedral framework in its XRD pattern bearing crystallite size in the range of 28 nm. The particle sizes were confirmed by morphological scanning of the sample. The optical properties of LaCrO3 nanopowders clearly indicated an interesting optical activity of LaCrO3 in the UV and visible ranges. The degradation activation energy (Ed) was calculated from the output of a moderate thermal programming profile at about 207.97 kJ·mol-1 using Kissinger equation. Capacity, impedance and AC resistance of the perovskites was obtained at 2.970 nF, 2.522 MΩ and 16.19 MΩ, respectively.

Open access
Dielectric properties of Bi-substituted LDHs synthesized by co-precipitation and sol-gel methods

Abstract

Magnesium-aluminum-bismuth layered double hydroxides (Mg3Al1−xBix; LDHs) were prepared using both coprecipitation and sol-gel methods. For the preparation of Mg/Al/Bi LDH by the co-precipitation method, the appropriate amounts of dissolved starting materials (Al(NO3)3 · 9H2O, Mg(NO3)2 · 6H2O and Bi(NO3)3 · 5H2O) were mixed with a solution of NaHCO3:NaOH. In the sol-gel processing, the precursor Mg–Al–Bi–O gels were synthesized using the same starting materials and ethylene glycol as complexing agent. The mixed-metal oxides obtained by subsequent heating of Mg–Al–Bi–O gels at 650 °C were reconstructed to Mg3Al1−xBix LDHs in water at 80 °C. All the synthesized products were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and dielectric measurements.

Open access