Papers by Keyword: Zinc Sulfide

Abstract: To meet the requirements of second generation photovoltaics, spin coating and RF magnetron sputtering techniques have been utilized to fabricate zinc sulfide thin films for buffer layer optimization. During fabrication process, substrate temperatures for spin coating and RF magnetron sputtering processes are kept at room temperature and at 200 oC, respectively. Thin films are annealed at 500oC for 1 hour in an inert environment to acquire crystallinity and uniform surface morphology. XRD analysis reveals that thin films fabricated by spin coating and RF magnetron sputtering exhibit wurtzite and zinc blende crystal structures, respectively. SEM shows that the surface morphology of thin films fabricated by both techniques is uniform and homogeneous without voids and cracks. EDS results indicate that thin films fabricated via spin coating have equal stoichiometric ratio of zinc to sulfur (1:1). Whereas, an unequal stoichiometric ratio of zinc to sulfur is detected in RF magnetron sputtered thin films. According to optical studies, spin coated zinc sulfide thin films have 67% transmission with an energy band gap of 3.62 eV. While, RF magnetron sputtered thin films have 76% transmission with a wide energy band gap of 3.70 eV. Electrical properties depict that thin films fabricated by RF magnetron sputtering have higher carrier concentration, lower resistivity and higher conductivity than spin coated thin films. In comparison, RF magnetron sputtered zinc sulfide thin films exhibit best structural and optoelectronic properties for buffer layer in second generation solar cells.

Abstract: Radioluminescence technologies are at the front line of the optic and electronic studies. Effective, self-contained and safe radioluminescent light sources can find their application in space industry, in medicine and in military technologies. The question of the performance improvement of the solid-state radioluminescent light sources (SRLS) without raising the included activity of working radionuclide can be solved by upgrading the phosphor crystalline structure. The electron-beam treatment for zinc-sulphide phosphors initial batch has been studied in a wide range of concentrations of the activating agent (Cu) for improving the radioluminescent performances of the phosphors, for creating the structural defects that form centers of luminescence. The changes of the phase composition were investigated under different synthesis conditions. It is revealed that electron-beam treatment of the initial batch leads to the growth of the wurtzite phase content in zinc-sulphide phosphors synthesized below the phase transition temperature. The changes of the phase content promote the spectral redistribution under the tritium beta-excitation. It is obviously the reflection of the fact of «green» luminescence centers rearrangement between the volume of the crystal and its surface. The correlations between structural configuration and performances of ionizing luminescence were found. Electron beam treatment gave the 20% increase of brightness of the radioluminescence. The achieved enhancement of luminescence performances allows the development of advanced tight-packed SRLS with minimal radioactivity and high energy-light conversion.

Abstract: Zinc can be found in oxide and sulfide forms in technogenic formations. Zinc oxide extraction from technogenic formations is widely used in industry. Removing zinc sulfide from technogenic formations is difficult and is currently almost never used. In the present work, the physicochemical features of zinc extraction from sulfide are considered. Process thermodynamic features and possible ways to extract zinc sulfide are shown. Also, ways of valuable commercial products, obtaining from the roasting products, are considered.

Abstract: In technogenic formations, zinc is found in oxide and sulphide forms. Extraction of zinc oxide from technogenic formations is widely used in industry. Removing zinc sulfide from technogenic formations is difficult and is currently almost never used. In the present work, the physicochemical features of zinc extraction from technogenic formations, in which zinc is presented in oxide and sulphide forms, are considered. Thermodynamic features of the processes and possible ways to extract zinc sulphide are shown. This work also considers the ways of valuable commercial products obtaining from the roasting products.

Abstract: The luminescent sensory systems based on manganese-doped zinc sulfide quantum dots were developed for aqueous environment monitoring. The structural, optical and sensory characteristics of quantum dots were investigated. The mechanism of ZnS:Mn²⁺ interaction with methane in the aqueous media, as well as factors that have a primary influence on the formation of the sensory response in the reaction with methane, were determined.

Abstract: In the chemical vapor deposited zinc sulfide, it often appears obvious light and dark growth bands along the growth direction, which will affect the homogeneity of optical properties of CVD ZnS and the efficiency of subsequent heat treatment. X-ray diffraction, Metallographic microscope and SEM were used to detect the crystal structure, grain size and microstructure, and the concentration of Zn and S in different bands was tested by EDTA titration, XRF, ICP and HF-combustion IR absorption spectrometric method. Results: Compared to the normal band, the grain size in the bright band was significantly larger, and the concentration of hexagonal phase in the bright band was lower, while the concentration ratio of Zn and S in the CVD ZnS did not have the regularity in the different bands. Combining with relevant knowledge about characteristics of the deposition process and crystal growth theory, the paper analyzes the formation mechanism of growth bands in CVD ZnS, and find that the main factor is the mutation of the concentration of the reactants in the deposition surface, affect the crystal nucleation rate and growth rate, eventually lead to the different grain morphologies, and even showing up the macroscopic growth bands. Compared with the actual process parameters, we have confirmed it and found out the main causes of mutation of the reactant concentration, this will have important guiding significance to the improvement of product quality in the future.

Abstract: This paper is describing an investigation of surfactants influence on zinc sulfide wetting by non-polar liquids and sphalerite concentrates pressure leaching parameters. Zinc sulfide preferential wettability by oil was tested in presence anionic surfactants with different chemical structures. Interfacial tension was determinated by the maximum liquid drop volume method. It allows to determine surfactant potential effectivity on pressure leaching of sphalerite concentrate. It is found that SDBS decreases zinc sulfide wettability by non-polar liquids in a greater degree than SDS and Ls. Combined addition of Ls and SDBS allowed to receive residues with optimal coarseness, eliminate pellet formation and increase zinc extraction.

Abstract: A simple aqueous based synthesis technique at room temperature was performed for preparation manganese-doped zinc sulfide quantum dots. Under 4 eV excitation quantum dots show photoluminescence bands at 2.11 and 3.1 eV corresponded to Mn²⁺ and intrinsic ZnS emission respectively. ZnS quantum dots were used as the luminescent sensing element for methane detection in aqueous media. The luminescent sensor response occurs due to photoinduced electron transfer from QDs to methane molecule resulting in QD luminescence quenching.

Abstract: Fluorescent zinc blende structured pure and Mn²⁺ doped ZnS quantum dots were prepared by simple aqueous based technique at room temperature. Under UV-excitation the quantum dots show photoluminescence bands at 2.1 and 3.0 eV corresponded to Mn²⁺ and ZnS intrinsic defect emission, respectively. The photocatalytic activity was tested for the photodegradation of methylene blue in aqueous solution. The influence of the Mn²⁺ concentration on the dye decolorization efficiency was studied. The highest photocatalytic degradation rate of methylene blue was obtained for ZnS quantum dots in glutathione shell doped with 0.5 at.% of Mn²⁺. The mechanisms of photoluminescence and photocatalytic activity were discussed.

Abstract: The microbial synthesized ZnS obtained from a pilot-scale sulfate reducing bacteria (SRB) fixed bed reactor was investigated as photocatalyst. The SRB fixed bed reactor as used to treat the Zinc containing wastewater with the influent concentration of 200~300 mg Zn/L. The microbial synthesized ZnS was used as photocatalyst for methylene blue (MB) photodegradation. The results indicated that the photodegradation process could be promoted when the dosage of microbial synthesized ZnS increased. High initial MB concentration could promote the photodegradation reaction. The excellent performance of microbial synthesized ZnS in photodegradation could be explained as the formation of ZnS nanoparticles. The photodegradation with microbial synthesized ZnS were simulated by pseudo-first-order kinetics model. The apparent first-order rate constant of the ZnS catalyst was 0.15 min^-1.