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The use of electromagnetic field in designing the high qualityal-alloys for hot forging process
No full textThis work presents a way to obtain the better quality of EN AW 7075 aluminum high-strength alloy by application of electromagnetic field (EMF) during the casting process. In this way, the uniform fine-grained microstructure, and hence the better mechanical properties of the alloy can be achieved. The microstructure and mechanical characterization for samples obtained with and without EMF were performed. The application of numerical simulation for hot forging process, using appropriate software, is efficient and highly useful tool for problem prediction in industrial production, reducing the time and costs in the process of development of new products. The input data of high strength Al-alloy EN AW-7075 is used for simulation because it enables the development of parts with complex dimensions and shape
Relation Between Edaphic Factors and Vegetation Development on Copper Mine Wastes: A Case Study From Bor (Serbia, SE Europe)
No full textThe relationship between edaphic characteristics and vegetation growing on mine wastes in the Bor region (East Serbia, SE Europe) was studied using multivariate statistical analysis. The influence of edaphic factors on the composition of plant life-forms was also investigated, since it could reflect strategies for the avoidance of or tolerance to disturbances of ecosystems. The goal was to provide potential models for the restoration and management of this and similar mine waste areas. The results of this study imply that soil textures, nitrogen contents, reclamation technology and the presence of hydrothermally altered andesite as the type of bedrock significantly influenced plant colonization and vegetation composition of the Bor mine wastes. These edaphic factors explained 30.3 % of the total variation in the vegetation data set. It was also revealed that the pattern of plant life-forms found on the considered site groups corresponded to the soil texture. Based on their relative abundance on the investigated sites and relationships with soil properties it is concluded that therophytes and geophytes are unsuccessful primary colonizers of the Bor mine wastes. Hemicryptophytes of psammophytic character were the most successful primary colonizers and therefore potential candidates for anthropogenically-assisted natural recovery. This study suggested that an assessment of edaphic factors should be widely used in the characterization of mine wastes prior to reclamation. Estimation of their role in the development of existing mine vegetation should predate reclamation procedures. Thus, approaches based on adequate plant life-forms should have a more prominent role in future mine reclamation schemes
Modified Natural Zeolites-Functional Characterization and Biomedical Application
No full textNatural and synthetic zeolites have emerged as potential materials for biomedical application in recent years. Zeolites are hydrated microporous tektoaluminosilicates consisting of three-dimensional frameworks of SiO4 and AlO4 tetrahedra linked through shared oxygen atoms. Clinoptilolite, a mineral from the heulandite group of zeolites, ((Na,K)6(Al6Si3O)O72·nH2O), is the most abundant sedimentary zeolite in nature. In this chapter an overview of surface modifi cation of clinoptilolite by interaction with cationic surfactants is given alongside with the methods used for characterization of the surfactant modifi ed zeolites (organozeolites/composites). Diff erent organozeolites were tested under conditions for adsorption of several mycotoxins commonly found in animal feed. Study of in vitro surfactant desorption in vitro followed by in vivo acute toxicity testing was used to demonstrate the nontoxic nature of these improved mineral materials. Functionality related characteristics of modifi ed natural zeolites were analyzed for investigation of their potential use as pharmaceutical excipients for modifi ed release of active pharmaceutical ingredients
Ceramic clays from the western part of the Tamnava Tertiary Basin, Serbia: Deposits and clay types
No full textBased on geological, mineralogical, physical, chemical and technological
investigations in the Tamnava Tertiary Basin near Šabac town (western
Serbia), deposits of ceramic clays were studied. These ceramic clays are
composed of kaolin-illite with a variable content of quartz, feldspars,
mica, iron oxides and hydroxides, and organic matter. Four main types of
commercial clays were identified: i) red-yellow sandy-gravely (brick clays);
ii) grey-white poor sandy (ceramic clays); iii) dark-carbonaceous (ceramic
clays); and iv) lamellar (“interspersed”) fatty, poor sandy (highly
aluminous and ferrous clays). Ceramic clays are defined as medium to high
plastic with different ranges of sintering temperatures, which makes them
suitable for the production of various kinds of materials in the ceramic industry
Mechanochemical-thermal process of obtaining masking pigment
No full textU ovom radu je ispitivana mogućnost dobijanja maskirnog pigmenta mehanohemijsko termičkim postupkom kao i energetsko učešće mehanohemijskog tretmana u dobijanju maskirnog pigmenta stehiometrijske formule Co0,51Zn0,29Mg0,41Cr1,24Al0,24Ti0,31O4. Mehanohemijski i termički tretirani uzorci smeše oksida radi dobijanja kompleksnog spinela su eksperimentalno istraživani u više serija opita, pri čemu su menjani parametri vezani za rad visokoenergetskog vibracionog mehanoaktivatora. Mehanohemijskom aktivacijom smeše oksida (Cr2O3, CO-oksida, ZnO, TiO2, MgO i Al2O3), u vibracionom mehanoaktivatoru sa prstenovima od 30; 60 i 90 min, a zatim termičkim tretiranjem u elektrootpornoj peći, pri vremenu zadržavanja uzorka od 1h, dobija se materijal spinelne strukture koji je pogodan kao maskirni pigment u vojnoj industriji.In this paper the possibility of obtaining masking pigment mechanochemically thermal process and the energy share of mechanochemical treatment in obtaining masking pigment by stoichiometric formula (Co 0.51 Zn 0.29 Mg 0.41 Cr 1.24 Al 0.24 Ti 0, 31 O 4). Mechanochemical and heat treated samples to obtain a mixture oxide spinel complex were experimentally investigated in a series of experiments wherein the altered parameters related to the operation of high energy vibratory mechanoactivator. Mechanochemical activation mixture oxide (Cr2O 3, C-O oxide, ZnO, TiO 2, MgO and Al 2 O 3), in vibration mechanoactivator with rings of 30; 60 and 90 min, and then, heat treatment in an electric furnace, with the sample retention time of 1 hour, the material is obtained, which spinel structure is suitable as the pigment in the masking military industry
Physicochemical investigation of some archaeometallurgical findings from locality Kmpije (Bor, Serbia)
No full textPreliminary results of physicochemical investigation of some archaeometallurgical findings from Kmpije locality in vicinity of Bor (Serbia) are presented in this paper. Ancient samples of prehistoric origin were investigated using different instrumental analytic methods-chemical, differential thermal, X-ray diffraction, and energy dispersive X-ray fluorescence analysis. Obtained results indicate to the presence of ancient metallurgical activities, so locality Kmpije may be considered as an archaeometallurgical site, which should be investigated more in future for more precise details
Chemometric approach for prediction of uranium pathways in the soil
No full textUnderstanding the effect of soil parameters (pH, Eh and organic and inorganic ligands availability) on uranium mobility under different geochemical conditions is fundamental for reliable prediction of its behaviour and fate in the environment. In this study, the impact of total and available phosphorus content, humus and acidity of Serbian agricultural soils on the content of total and available uranium were evaluated by Response Surface Methodology (RSM), second order polynomial regression models (SOPs) and artificial neural networks (ANNs). The performance of ANNs was compared with the performance of SOPs and experimental results. SOPs showed high coefficients of determination (0.785-0.956), while ANN model performed high prediction accuracy: 0.8893-0.904. According to the results, total and available uranium content in the soil were mostly affected by pH, statistically significant at p LT 0.05 level. For the same responses the total phosphorus was found to be also very influential, statistically significant at p LT 0.05 and p LT 0.10 levels. The impact of available phosphourus and humus was much more influential on total and available uranium content, compared to total phosphorus content. Proposed chemometric approach will be very helpful in preserving the natural resources and practical application for risk assessment modeling of uranium environmental pathways
The influence of melting atmosphere and casting on the mechanical and structural characteristics of palladium-nickel alloy
No full textThe main aim of the research, presented in this paper, is to analyze the structural conditions of the PdNi5 alloy depending on the applied melting atmosphere and casting, as well as monitoring changes in the structural and mechanical properties of PdNi5 alloys after homogenization annealing in order to obtain the required quality castings for further plastic processing -rolling. In one case, the melting and casting of the alloy was done in medium frequency induction furnace in an charcoal atmosphere, while in the second, in a vacuum atmosphere. Hardness and the content of C, H, S were determined, and structural analysis of the cast samples using SEM and EDS analysis, was performed. Furthermore, after homogenization annealing at 800 degrees, 900 degrees and 1000 degrees C, lasting 90 minutes, the hardness was determined and structural analysis with an optical microscope was performed and samples are subjected to plastic processing - rolling, with deformationdegrees epsilon = 92%. Based on the analysis of the results, it was found that the melting and casting in vacuum with optimum heat treatment, could be applied to obtain satisfactory castings and structural characteristics for further plastic processing - rolling. The results presented in this paper may offer further knowledge of the effects various parameters have on the properties of palladium-nickel alloy
Recycling of silver-plated brass for production of high purity copper and ultrafine silver powder for electric contacts
No full textThe paper presents an improved process for recycling of silver-plate brass housing. Silver and copper are recovered with a purity of 99.99 % and 99.90 %, respectively, with the aim of obtaining materials of higher value using additional procedures based on the same process and equipment. The novel approach with subsequent electrorefining yields copper of 99.99 % purity with BS EN 1978:1998 (Cu-CATH-1) quality and is referred to as LME grade A. Additional processing of silver results in superfine, micro-sized Ag powder with partie size from 0.14 to 1.13 mu m and purity of 99.999 %. Copper electrorefining tests were performed using 1.50 dm(3) of synthetic electrolyte in a 2 dm(3) electrolytic cell. Effects of current density and electrolyte composition were investigated. Optimal current density for the first and second refining was 120 A/m(2) and 200 A/m(2), respectively. Additional refining of silver was performed by chemical reduction from an aqueous solution. Optimal results were obtained with ascorbic acid as a reduction agent in concentration of 0.1 mol/dm(3) and polyvinylpyrrolidon as a protective agent in concentration of 2 % by mass. The investigation results could be adopted into production
Definition the technology method of apatite flotation concentration from the phosphate deposit 'Lisina'
No full textU radu je prikazan značaj fosfata u svetu, kao i problemi koji se javljaju u postupku pripreme siromašnijih ruda fosfata iz kojih se koncentrat fosfata dobija postupkom flotacijske koncentracije. Selektivnim flotiranjem aptita iz silikatnih i oksidnih ruda se dobijaju koncentrati apatita, dok definisanje postupka selektivnog flotiranja apatita iz karbonatnih ležišta predstavlja veliki problem u svetskim razmerama. U eksperimentalnom delu ovoga rada su prikazani rezultati laboratorijskih opita flotiranja rude fosfata iz ležišta 'Lisina'- sa površinskog dela -lokalitet 'Panjevica'. Dobijeni rezultati su omogućili definisanje postupka flotiranja u kontinualnim uslovima rada.This paper presents the importance of phosphate in the world, and the problems that arise in the process of preparing the low-grade phosphate ore for obtaining the phosphate concentrate using the flotation concentration. The apatite concentrates are obtained using the selective flotation from the silicate and oxide minerals while defining the process of selective flotation of apatite from carbonate deposits is the major problem worldwide. The experimental part of this paper presents the results of laboratory flotation tests of phosphate ore from the surface part of the location 'Panjevica' of the deposit 'Lisina'. The results have enabled definition of the flotation process in continuous conditions of work