Facile Synthesis of Cu2ZnSnS4 Photovoltaic Absorber Thin Films via Sulfurization of Cu2SnS3/ZnS Layers

Copper zinc tin sulfide (Cu₂ZnSnS₄) has been receiving a lot of attention in recent years as a new, alternative absorber for the production of cheap thin film solar cells owing to the high natural abundance of all the constituents, its tunable direct-band-gap energy, and its large optical absorption coefficient. In addition, to overcome the problem of expensive vacuum-based methods, solution-based approaches are being developed for Cu₂ZnSnS₄ deposition. In this study, Cu₂ZnSnS₄ thin films were grown on soda lime glass substrates via the sulfurization of solution grown Cu₂SnS₃/ZnS stacked sulfide layers. A new facile route to overcome the difficulty of depositing Cu₂ZnSnS₄ thin film with a desired stoichiometric composition in a single cation solution has been presented. The influences of deposition cycles of layers on the morphological, compositional, structural, and optical properties of the samples were investigated. It was observed from scanning electron microscopy (SEM) images that the films were continuous and composed of homogenously distributed large grains. Possible chemical formulations of the best samples were predicted to be Cu_1.99Zn_1.25Sn_1.00S_3.76 and Cu_1.97Zn_1.03Sn_1.29S_3.71 via energy-dispersive X-ray spectroscopy (EDXS) results. The X-ray diffraction (XRD) patterns of the samples matched very well with the reference values. The Raman-scattering analysis of the films proved the phase purity of the CZTS samples. The optical absorption coefficient of the films was found to be about 10⁴ cm^?1 based on absorbance spectroscopy. The optical band gaps of the films were estimated to be between 1.36 and 1.50 eV. From these we are able to conclude that CZTS thin films can be effectively obtained via the vacuum-atmosphere sulfurization of Cu₂SnS₃/ZnS stacked sulfide layers.     

Geothermal energy potentials in the province of Vojvodina from the aspect of the direct energy utilization

The interest in increasing the participation of renewable energy sources (RES) in energy production arises with increasing population and growing demands for energy production and consumption, as well as the fact of the limited fossil fuels reserves. RES in the energy balance of any country has their share of energy, socio-economic and environmental benefits. Investment in energy sector in the RES domain enables Vojvodina Province to reduce energy dependence on the fossil fuel market.From the total RES potential in Vojvodina Province that is 1293 ktoe/year, around 1.7% is located in existing geothermal sources. There are 73 drills with a total capacity of 72.6 MW from which 65 drills are tested positive. Currently, 15 wells are in production, with a total power of 17.7 MW. There are 27 drills that have never been in production and which are perspective, with a total power of 42.8 MW.The aim of this paper is to perform data analysis of direct geothermal energy utilization according to the water temperature and geothermal fluid flow. According to the results of the analysis recommendations for geothermal energy utilization are given within certain sectors: agriculture (aquaculture and greenhouses), heating of the facilities and pools, industrial applications and balneology.     

Experimental investigation of pyrolysis process of woody biomass mixture

This paper describes an experimental investigation of pyrolysis of woody biomass mixture. The mixture consists of oak, beech, fir, cherry, walnut and linden wood chips with equal mass fractions. During the experiment, the sample mass inside the reactor was 10 g with a particle diameter of 5-10 mm. The sample in the reactor was heated in the temperature range of 24-650℃. Average sample heating rates in the reactor were 21, 30 and 54 ℃/min. The sample mass before, during and after pyrolysis was determined using a digital scale. Experimental results of the sample mass change indicate that the highest yield of pyrolytic gas was achieved at the temperature slightly above 650℃ and ranged from 77 to 85%, while char yield ranged from 15 to 23%. Heating rate has sig- nificant influence on the pyrolytic gas and char yields. It was determined that higher pyrolysis temperatures and heating rates induce higher yields of pyrolytic gas, while the char mass reduces. Condensation of pyrolytic gas at the end of the pyrolysis process at 650℃ produced 2.4-2.72 g of liquid phase. The results obtained represent a starting basis for determining material and heat balance of pyrolysis process as well as woody biomass pyrolysis equipment.     

Influence of Preservative Concentration,pH Value and Fat Content in Raw Milk at Detection Limit of Microbial Inhibitor Tests (Delvotest® Accelerator) for Amoxicillin and Oxytetracycline

The presence of antibiotic residues in raw milk is a big threat not only to the dairy industry but also to public health. Therefore, it is very important to detect antibiotic residues in raw milk. There are many reliable antibiotic test used in dairy laboratories. Unfortunately, some factors can affect the results causing, so-called false-positive results. The aims of this paper are to check the detection limits of microbiological inhibitor test with test organisms Geobacillus stearothermophilus var. calidolactis, which are provided on Delvotest® Accelerator instrument (DSM, The Netherlands) for antibiotics amoxicillin and oxytetracycline and to examine the influence of variations of milk fat contents, pH values and azidiol concentrations in raw milk on detection limits, e.g., test results. The obtained results showed that detection limit for amoxicillin is 3 μg/L and oxytetracycline 250 μg/L; concentration of preservative azidiol of 0.1 mL per 40 mL of milk does not affect the detection limits of the test; microbiological inhibitor test is extremely sensitive to low pH value of samples so, it is recommended to avoid testing milk samples with low pH value, or to adjust the sample’s pH value by addition of some base; and that fat content in raw milk up to 5 % does not affect the detection limit of the methods for amoxicillin and for oxytetracycline.     

Modification of glassy carbon properties under low energy proton irradiation

Glassy carbon plates were irradiated with 15 keV H⁺ ion-beam in the fluence range of 1 × 10¹⁶–3 × 10¹⁸ ion cm⁻². The influence of ion irradiation on surface morphology and topology was examined by scanning electron and atomic force microscopy. Structural changes were monitored by Raman spectrometry, while changes of wettability and the content of surface oxygen complexes were examined by contact angle measurements and temperature programmed desorption. Elastic recoil detection analysis was applied for determination of hydrogen concentration profiles in irradiated samples. Cyclic voltammetry was used for the assessment of the electrochemical properties of modified glassy carbon electrodes. It was concluded that there is critical fluence range (2 × 10¹⁷–5 × 10¹⁷ ion cm⁻²) inside of which significant changes of glassy carbon properties occur.     

Microstructure Development in Low-Antimony Oxide-Doped Zinc Oxide Ceramics

The grain growth of ZnO ceramics sintered with low additions of Sb₂O₃ (<500 ppm of Sb) was investigated. Additions of Sb<250 ppm resulted in a coarse-grained microstructure with large ZnO grains (55–70 μm), much larger than the grain size of ZnO ceramics without any Sb₂O₃ addition (45 μm). The addition of 500 ppm of Sb resulted in a fine-grained microstructure with an average ZnO grain size of about 12 μm. The results are explained by an inversion-boundary (IB) -induced grain-growth mechanism. The grain-growth exponent has a value of about 2 as long as the grains containing IBs grow at the expense of IB-free grains. It increases to about 4 after the IB-containing grains impinge on each other, and achieves values above 10 for additions of 500 ppm of Sb when IBs nucleate in nearly all the ZnO grains so that grains with IBs prevail in the microstructure at an early stage in the grain-growth process.     

High-performance charge storage by N-containing nanostructured carbon derived from polyaniline

Nitrogen-containing nanostructured carbon materials, C-nanoPANI, C-nanoPANI-DNSA and C-nanoPANI-SSA, were prepared by the carbonization of nanostructured polyaniline (PANI) doped with sulfuric acid, 3,5-dinitrosalicylic acid (DNSA), and 5-sulfosalicylic acid (SSA), respectively. The charge storage ability of these materials was investigated in alkaline solution. It was found that the specific capacitance increased in the order: C-nanoPANI-DNSA < C-nanoPANI < C-nanoPANI-SSA. The highest capacitance, amounting to 410 F g^?1 at a scan rate of 5 mV s^?1, was found for C-nanoPANI-SSA. At a large rate of 10 A g^?1, its capacitance displayed a stable value close to 200 F g^?1. To explain the observed differences in charge storage properties, the materials were characterized by different techniques able to ascertain their morphology, elemental composition, nitrogen surface concentration, chemical state of nitrogen, pore structure and electrical conductivity. All materials were essentially microporous with relatively small fraction of mesopores and displayed conductivities in the range 0.32–0.83 S cm^?1. The best charge-storage performance of C-nanoPANI-SSA was attributed to its highest surface fraction of nitrogen, the highest surface content of pyridinic nitrogen groups, and the highest electrical conductivity, as well as to its well-balanced micro- and mesoporosity and highest content of mesopores.     

Potential of earthing grid in heterogeneous soil

Calculation of the scalar electric potential of an earthing grid in heterogeneous soil is obtained by the finite element technique combining differential and integral formulations of the problem. Such a combined formulation made it possible to generate easily the mesh of finite elements and to divide the problem domain into a sufficiently small number of large finite elements. The unbounded domain of calculation is solved by using mapped infinite elements. The contribution of singular sources is represented by the analytical expression, and included in the approximation function of the potential. A sufficiently satisfactory approximation is realized with a small number of singular source images, obtained by local imaging of sources within a finite element on its boundary surfaces. The calculation accuracy is tested on examples solvable by an average potential method which is based on an integral formulation of the problem.     

Growth of Transparent and Conductive Polycrystalline (0001)‐ZnO Films on Glass Substrates Under Low‐Temperature Hydrothermal Conditions

Flat panel display technology seems to be an ever‐expanding field developing into a multibillion dollar market. A set of technical solutions involve a transparent conducting film (TCF) that is today still dominated by indium‐tin‐oxide (ITO). In a race to find alternatives that would avoid the indium pitfalls, mainly due to its increasing price and limited natural availablity, replacement materials have been extensively investigated. This work demonstrates that by exploiting basic principles of crystal growth in geometrically constrained conditions, zinc oxide (ZnO) could easily be utilized for this purpose. ZnO layers were grown on inexpensive glass substrates via low‐temperature citrate‐assisted hydrothermal (HT) method. It was shown that in the nucleation stage the crystal growth can be efficiently controlled by spatially confined oriented growth (SCOG) mechanism to produce smooth and dense (0001) oriented polycrystalline ZnO films with superb optical properties. Our products show optical transparency of 82% and surprisingly low sheet resistance for undoped ZnO, only in the order of few 100 Ω sq^?1. We believe that a very high degree of self‐organization between the ZnO crystals in our polycrystalline films grown under controlled SCOG conditions is main reason for the highest so far reported transparency to conductivity ratio for undoped ZnO thin film ceramics.