Cerium and tin co-doped cadmium zinc sulfide nanoparticles (CdZnS:Ce)Sn were synthesized by chemical bath deposition method with a fixed concentration of Ce (3.84 mol%) and three different concentrations of Sn (2 mol % and 4 mol% and 6 mol%). They showed broad photoluminescence spectra in the visible region under the ultraviolet excitation with a wavelength of 325 nm. The photoluminescence emission peaks were obtained at 540 nm, 560 nm and 570 nm for CdZnS, CdZnS:Ce and (CdZnS:Ce)Sn thin films, respectively having different concentrations of Sn. It has been observed that the photoluminescence emission peak shifted to higher wavelength region with an increase in intensity by Ce doping and Ce–Sn co-doping. Further enhancement in luminescence peak intensity has been observed by increasing concentration of Sn in (CdZnS:Ce)Sn films. Average crystallite size, measured from XRD data, was found to be increased with increasing concentration of Sn. An increase in the concentration of Sn shifted the UV-Vis absorption edge toward the higher wavelength side. Energy band gap for undoped CdZnS and Ce–Sn co-doped CdZnS varied from 2.608 eV to 2.405 eV. The SEM micrographs of CdZnS and (CdZnS:Ce)Sn films showed the leafy-like and ball-like structures. The presence of Sn and Ce was confirmed by EDAX analysis.
Antonio Mario Federico, Osvaldo Bottiglieri, Francesco Cafaro and Gaetano Elia
Water infiltration through coal stocks exposed to weather elements represents a key issue for many old mining sites and coal-fired power plants from the environmental point of view, considering the negative impact on human health of the deriving groundwater, soil and air pollution. Within this context, the paper investigates the hydraulic behaviour of a self-weight compacted unsaturated coal mass and its impact on the numerical prediction of infiltration induced by rainfall events. In particular, the work focuses on the experimental investigation carried out at different representative scales, from the grain scale to physical modelling. The material, when starting from uncompacted conditions, seems to be characterized by metastable structure, which tends to collapse under imbibition. In addition, direct numerical predictions of the seepage regime through a partially saturated coal mass have been performed. As the compaction of the coal stock induced by dozers has not been taken into account, the numerical simulations represent a conservative approach for the assessment of chemical pollution hazard associated to water infiltration into a real stockpile under operational conditions.
Jan Maciejewski, Sebastian Bąk and Paweł Ciężkowski
The problem of numerical simulation of the material interface response under monotonic and cyclic loading is of fundamental scientific and engineering importance. In fact, such interfaces occur in most engineering and geotechnical structures. The present work is devoted to the deformational response analysis of contact interfaces under monotonic and cyclic loads. The class of materials includes rock and structural joints, soil structure interfaces, masonry and cementitious joints, localized shear bands and so on.
The aim of the proposed model is to simulate the cyclic shear test under constant normal load. The associated dilatancy effect is associated with the configurational effects of asperity interaction or dilatancy of wear debris layer. The large primary asperities are assumed as responsible for interfacial dilation and small size asperities as governing frictional sliding and hysteresis response. The elliptic loading yield function is assumed to translate and rotate during progressive or reverse loading events. The model formulation is discussed and confronted with experimental data.
Paweł Ciężkowski, Jan Maciejewski, Sebastian Bąk and Arkadiusz Kwaśniewski
The results of studies of the crushing process in a double toggle jaw crusher are presented. This process was carried out on six sets of crushing plates. The first three of them are used in industrial crushers – plates with a flat working surface and a triangular profile (in this work, under consideration were profiles with teeth angle γ = 90°). The fourth and fifth type refer to plates with a variable pitch t and teeth height with a triangular shape of the teeth. In the sixth solution, plates with variable pitch and width of the wedged teeth are proposed.
The results of the basic process parameters are shown, that is, average degree of fineness n, technical performance Wt, crushing energy L and crushing force F, sieve analysis of crushing product. The obtained results are the basis for the assessment of the suitability of various types of plates, especially plates with a new profile, which have an altered shape in comparison with the plates used in crushers so far.
The crushing tests were carried out with the same dimension of outlet slot er = 24 mm, close to the pitch size for plates with triangular profile. Tests were performed on the “Mucharz” sandstone. Samples from a series of blocks of different size and geometric shape were prepared. This work also presents feed mass influence on crushing process efficiency.
The plates with variable pitch and width of teeth are beneficial because of lower crushing force and energy.
Goran Tasev, Todor Serafimovski, Matej Dolenec and Nastja Rogan Šmuc
The Zletovo is lead–zinc (Pb–Zn) deposit, adjacent to the Plavica volcanic centre (R. Macedonia) with high-sulphidation and porphyry mineralisation. The analysis of fluid inclusions showed homogenisation temperatures in the range 335–145°C, which reflects phases of pulsation of hydrothermal solutions and defined into four groups from the lowest to the highest temperatures. The frequency of the homogenisation temperatures ranged from 265 to 125°C and with the most dominant from 245 to 225°C, from 225 to 205°C and from 145 to 125°C. Also, it was confirmed that hydrothermal ore-bearing solutions were defined as Na-Cl-type with range from 4.4 to 8.6 wt% NaCl equivalent. The latest stage salinities ranged from 3 to 12 wt% NaCl equivalent, where those from 10 to 12 wt% and from 6 to 8 wt% NaCl equivalent, prevailed. This suggests that hydrothermal solutions within analysed quartz grains were at final mineralizing phase. Density of fluid inclusions ranged from 0.7 to 0.95 g/cm3. Calculated pressures and paleo-depths of mineralisation ranged from 14 to 130 bar and from 0.6 to 0.8 km.
Pravin Kumar Singh, S.K. Tripathi and D.K. Dwivedi
Thin films of Ge10−xSe60Te30Inx (x = 0, 2, 4 and 6) were developed by thermal evaporation technique. The annealing effect on the structural properties of Ge10−xSe60Te30Inx (x = 0, 2, 4 and 6) films has been studied by X-ray diffraction (XRD). The XRD results indicate amorphous nature of the as-prepared films whereas crystalline phases in annealed films were identified. Structural parameters such as average crystallite size, strain, and dislocation were determined for different annealing temperatures. Effect of annealing on optical constants of prepared films has been explored using UV-Vis spectrophotometer in the wavelength range of 400 nm to 1000 nm. Various optical constants were determined depending on annealing temperature. It has been noticed that the film transparency and optical bandgap EG have been reduced whereas the absorption coefficient α and extinction coefficient k increased with increasing annealing temperature. It was found that the prepared samples obey the allowed direct transition. The reduction in optical bandgap with annealing temperature has been described by Mott and Davis model. Due to annealing dependence of the optical parameters, the investigated material could be utilized for phase change memory devices.
A. Mahudeswaran, A. Jeeva, J. Chandrasekaran and P.S. Vijayanand
In this article, we report the synthesis and characterization of silver dispersed poly(m-toluidine-co-2-bromoaniline) copolymer synthesized by chemical oxidative polymerization method. The synthesized copolymer composites were subjected to different analytical characterization methods, such as FT-IR, UV, XRD, SEM, photoluminescence and electrical conductivity studies. All the polymer samples are found to be soluble in common organic solvents. UV absorption spectra show a red shift when silver nanoparticles are dispersed in the copolymer. The characteristic peaks observed in FT-IR spectra confirm the formation of the copolymer. XRD pattern reveals the crystalline nature of the copolymer composites and sharp peaks in the spectra confirm the presence of silver particles. The silver nanoparticles change the surface morphology in the form of perfect encapsulation. The electrical conductivity of the polymer composites is found to vary from 10−4 S/cm to 10−6 S/cm. PL study reveals the charge transfer between the copolymer and the silver particles.
Electro-optic (EO) polymers, possessing high EO coefficient and low dielectric constant, are considered to be a new generation of nonlinear optical materials that have great application prospect in photo-communication, information storage, and data processing. The host-guest structure of EO polymers is the most typical one in this field. However, the phase separation during polarization between the host polymer and the guest nonlinear optical molecule (NLO) limits potential applications of the material. To solve the problem, a new synthetic method was designed in this paper. First, 2,4-dinitroaniline was grafted to phenol polyphosphazene by chemical method for polar improvement of the main chain. Then, another small NLO molecule was mixed into the polymer by physical method for further improvement of EO coefficient. The preparation process was studied and the structure of the product was characterized. The effects of different NLO mixing proportions and different polarizing temperatures on EO coefficient were investigated in details. Orientation stability of the sample was tested. Experimental results show that our products possess not only high EO coefficient but also good phase stability, which makes them good candidates for the application in information technology.
The present study shows the results of a 2D local seismic response (LSR) analysis, simulated for a geomechanical model consisting of a layered carbonate rock mass with hypogean karst caves and a structural– lithostratigraphic complex setting, in an area within the Municipality of Turi (Apulia, Italy). In this case study a Distinct Element Code (DEM) code (UDEC) was used for the LSR simulations conducted on a model both in the absence and in the presence of two overlapping karst caves. The preliminary stress–strain model analysis show some tensile yielding points clustered on the roof of the upper karst cave, already in static conditions, and the phenomenon becomes even more noticeable in dynamic conditions. This is perfectly in agreement with the real occurrence of a sinkhole that brought to the light the underlying karst cave, in the case study area, in the recent past.
The amplification/deamplification factor (FA) was calculated as the ratio of the top value to the bottom value in the model, both of the max X-acceleration and of the spectral Fourier amplitude in three different ranges of frequencies, in order to estimate the effects of LSR on the X-component of the seismic input. According to the previous studies, the results obtained show a generalised deamplification of the seismic ground motion at the top of the model, both without and with underground karst caves, caused by the presence of the upper karst cave and by the seismic energy absorption because of layers’ discontinuity.
In a piled-raft foundation, the interaction between structural elements and soil continuum can be simulated very precisely by numerical modeling. In the present study, 3D finite element model has been used to examine the settlement, load-sharing, bending moment, and shear force behavior of piled-raft foundation on different soil profiles for different load configurations and pile-raft configurations (PRCs). The model incorporates the pile-to-soil and raft-to-soil interactions by means of interface elements. The effect of parameters such as pile spacing and raft thickness are also studied. For any soil profile, larger pile spacing is observed to be more efficient in reducing the average settlement and enhancing the load-sharing coefficient. The smaller pile spacing is observed to be efficient in reducing the differential settlement. For any soil profile, the behavior of piledraft foundation is significantly affected by the PRCs and load configurations. Furthermore, the raft thickness has significant effect on settlement, bending moment, and shears force. Thus, the results of the present study can be used as guidelines for analyzing and designing large piled-raft foundation.