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Pattern recognition techniques are applied to various morphological descriptors to monitor the formation and propagation of surface defects of materials subjected to thermal shock. A low-cement high-alumina castable was synthesized, cured, sintered, and exposed to thermal stability testing using the water quench test. After a certain number of thermal shock cycles, photographs of the samples’ surfaces were taken and subjected to image analysis. The influence of the sintering temperature on the morphology of the detected defects was studied using principal component analysis (PCA) as a pattern recognition technique that is the most informative for extracting possible differences. The morphological descriptors of the defects correspond to the previous results regarding the influence of sintering temperature on the structure of a castable during thermal shocks.

Metals : open access journal 11(7), 997 (2021). doi:10.3390/met11070997 special issue: "Special Issue "Advances in Understanding of Unit Operations in Non-ferrous Extractive Metallurgy" / Special Issue Editors Dr. Srecko Stopic, Prof. Dr. Bernd Friedrich", Published by MDPI, Basel

The problem of subsidence and damages on buildings above mining works is an inevitable consequence of underground coal mining in large mining basins. Significant development of various methods for prediction of the displacement parameters of the undermined terrain took place in the period from the middle of the last to the beginning of this century. In this paper, a new mathematical model of the stochastic Pataric-Stojanovic method for the predictive subsidence calculation is developed. A case study, as an example for the practical application of the proposed stochastic method, is given for the underground coal mine “Rembas”- Resavica, Serbia. An original MITSOUKO program package, supported by spatial analyses in the Geographic Information System (GIS), was developed for the predictive subsidence calculation based on the stochastic method proposed by the authors Pataric and Stojanovic. The comparative analysis of predicted and measured subsidence values confirms the possibility of using this stochastic method for predictive subsidence calculation in practice, which is a necessity of modern mining.

High-temperature materials are used in a wide range of industries and applications such as gas turbine engines for aircrafts, power and nuclear power plants, different types of furnaces, including blast furnaces, some fuel cells, industrial gas turbines, different types of reactors, engines, electronic and lighting devices, and many others. Demands for high-temperature materials are becoming more and more challenging every year. To perform efficiently, effectively and at the same time to be economically viable, the materials used at high temperatures must have certain characteristics that are particularly expected for applying under such extreme conditions, for example, the strength and thermal resistance. In the present review, some important requirements that should be satisfied by high temperature materials will be discussed. Furthermore, the focus is put on refractory concretes, ceramics, intermetallic alloys, and composites as four different categories of these materials, which are also considered in respect to possibilities to overcome some of the current challenges. U visokotemperaturske materijale spada široki spektar materijala koji se koriste u industriji, za primenu poput turbina za motore i avione, termo i nuklearne elektrane, različite tipove peći uključujući visoku peć, gorivne ćelije, turbine za različiite namene u industriji, razne vrste reaktora, motora, uređaja u elektronici i osvetljenju, kao i mnoge druge. Svake godine zahtevi za visokotemperaturske materijale postaju sve izazovniji. Da bi se ostvarila efikasnost i efektivnost, i da bi se istovremeno postigla ekonomska održivost, materijali koji se koriste na visokim temperaturama moraju zadovoljiti određene zahteve i imati svojstva koja se očekuju u tako ekspremnim uslovima, kao što su, na primer čvrstoća i otpornost na povišene temperature. U ovom preglednom radu razmatrani su neki od značajnih zahteva koji moraju biti zadovoljeni za visokotemperaturske materijale. Rad se odnosi na vatrostalne betone, keramiku, intermetalne legure i kompozite, kao četiri različite kategorije ove vrste materijala. Navedeni materijali su razmatrani u pogledu mogućnosti prevazilaženja nekih trenutnih izazova.

The intent in this paper is to define how the batch equilibrium results of copper removal from a synthetic solution on natural zeolite can be used for prediction of the breakthrough curves in the fixed-bed system for both a synthetic solution and wastewater. Natural zeolite from the Vranjska Banja deposit, Serbia, has been fully characterized (XRD, chemical composition, DTA/TG, SEM/EDS) as a clinoptilolite with cation exchange capacity of 146 meq/100 g. The maximum adsorption capacity (qm) in the batch of the mono-component system (synthetic copper solution) obtained using the Langmuir isotherm model was 7.30 and 6.10 mg/g for particle size below 0.043 and 0.6&ndash, 0.8 mm, respectively. Using the flow-through system with the 0.6&ndash, 0.8 mm zeolite fixed-bed, almost double the adsorption capacity (11.2&ndash, 12.2 mg/g) has been achieved in a saturation point for the copper removal from the synthetic solution, compared to the batch. Better results are attributed to the constant high concentration gradient in flow-through systems compared to the batch. The complex composition of wastewater and large amounts of earth alkaline metals disturb free adsorption sights on the zeolite surface. This results in a less effective adsorption in flow-through systems with adsorption capacity in breakthrough point of 5.84 mg/g (~0.95 &times, qm) and in a saturation point of 7.10 mg/g (~1.15 &times, qm).

Mining induced the ground subsidence and consequently, damages on objects above excavation works is a serious problem all over the world. In this paper, a new approach for subsidence and deformation prediction based on the stochastic Pataric-Stojanovic method is presented. Since the calculation using the equations of this method is very complex, the original computer program package with the title MITSOUKO has been purposely designed. The MITSOUKO program enables calculating at any point of the land surface and representing the results owing to the possibility of their integration and further processing in the Geographical Information System (GIS). The components of the GIS are used to realize the spatial analysis.

Mechanical shock of zircon based ceramic induced by cavitation erosion testing was investigated in this study. Several parameters were followed in order to determine level of material degradation during the cavitation erosion testing. Mass loss was taken as a conventional criterion for material degradation, while the level of surface degradation was evaluated by image and thermal imaging analyses. Results show high cavitation resistance of zircon ceramics and their suitability when vigorous cavitation erosion environment is expected. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 33007, Grant no. III 45012, Grant no. TR 35002 and Grant no. OI 172060]

Serbian lignite from Kolubara deposit was used as a low cost adsorbent for removal of copper ions (Cu2+) from aqueous solutions. Lignite was subjected to the elementary and technical analysis as well as BET and FTIR analysis due to complete characterization. Basic comparison between lignite and activated carbon was also done. As a method, batch adsorption procedure was applied. Adsorption efficiency was studied as a function of the initial metal concentration, pH of the solution, contact time, and amount of the adsorbent. Optimum removal of copper ions was achieved at pH values of 5.0. About 90% of copper cations were removed in 5 min of contact time from the solution with the lowest copper concentration (50 mg Cu2+/l) regardless adsorbent amount, while the same effect of adsorption was achieved in 60 min in case of solutions with higher concentrations of copper. It was concluded that the effect of adsorbent amount on adsorption kinetics is evident but not crucial. It was proved that the experimental results of copper adsorption fit well to a Langmuirian type isotherm which was used to describe monitored adsorption phenomena. The calculated adsorption capacities of lignite for copper adsorption decrease with increasing adsorbent amount. The study proved that tested lignite is very efficient adsorbent material, especially in case of low copper concentration in aqueous solution where the usual methods are either economically unrewarding or technically complicated. This behavior can be explained by FTIR spectrum despite a small specific surface area of lignite. Namely, many bands (peaks) are attributed to the functional groups that they are involved in chemisorption and ionic exchange, basic mechanisms of copper adsorption. (C) 2011 Elsevier B.V. All rights reserved.

Coating materials are widely used in refractory lining to prevent different deleterious effects such are reactions on the mold-metal contact surface, abrasion from liquid metal or alloy, gasses, slags, and other materials in contact with the coating. In this paper, behavior of cordierite based coating exposed to the cavitation erosion was investigated. Cordierite samples sintered at 1200 and 1400 degrees C were used for the tests. Mass loss, level of surface degradation obtained using image analysis and thermal imaging analysis were applied for the cavitation erosion evaluation. Results showed that the cordierite samples can be successfully used in conditions where the cavitation resistance is required. This is the peer-reviewed version of the article: Pavlović, M., Dojčinović, M., Martinović, S., Vlahović, M., Stević, Z.,& Volkov-Husović, T. (2016). Non destructive monitoring of cavitation erosion of cordierite based coatings. Composites Part B-Engineering, Elsevier., 97, 84-91. [https://doi.org/10.1016/j.compositesb.2016.04.073] The published version: [https://cer.ihtm.bg.ac.rs/handle/123456789/1858]

The purpose of this study was to investigate behavior and degradation level of refractory concrete sintered at different temperatures during the thermal stability testing. Alumina based low cement castable was synthesized, cured, and then sintered at 1100, 1300, and 1600 degrees C with dwell time of 3 h. Prepared samples were subjected to the water quench test. Behavior of the refractory concrete and determination of surface and internal degradation level during the testing were monitored by ultrasonic measurements and image analysis. Overall material degradation was determined by measuring the strength degradation of samples using the standard laboratory procedure. The samples sintered at 1300 degrees C showed the best behavior under thermal shock, since they withstood 110 cycles of water quench without breaking. It was evident that during the thermal shock, surface and interior of the samples sintered at 1600 degrees C behave differently compared with those sintered at 1100 and 1300 degrees C.