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The intra-Mesozoic bauxite-bearing truncations of the peri-Neotethyan realm (Dinarides/Vardar Zone): A multidisciplinary approach shedding new light on the Neocimmerian event
No full textOnce coupled with global eustatic levels, bauxites, breccias, unconformities, and hiatuses are significant markers
of compressional geodynamics. Most Balkan intra-Mesozoic bauxites, embedded within widespread Triassic
carbonate parental sequences, are dominantly distributed in the tectonically exhumed broader Neotethyan realm
(Dinarides s.l.). The same mid-Mesozoic stratigraphic interval within the Vardar Zone contains fewer bauxites
(East Vardar Zone), exposing abundant corresponding depositional truncations, with occasional nappe stacking
configuration and metamorphism. This study, which initially acquired data from a large number of mid-Mesozoic
unconformities, carbonate breccias, and similar age bauxites spreading across Dinarides s.l., Serbia, Bosnia and
Herzegovina, Montenegro, Croatia (Inner and External Dinarides, Western and East Vardar Zone), including
Hellenides in Greece, has provided valuable paleogeographic and geodynamic insights. The findings of this
study, combined with the available mineralogical and geochemical data, deformation, including the resulting
provenances of intra-Mesozoic bauxite deposits, have led to a complex and intriguing discussion on the tectonic
origin of similar age unconformities across Dinaride-Hellenide and Vardar Zone Neotethyan regions. These
Dinaride-Hellenide intra-Mesozoic unconformities, carbonate breccias, and widespread bauxites are a fascinating
puzzle as no study deals with the complex and controversial processes of repeated regional-scale uplifts, erosion,
and bauxite formation. The ambiguity revolves around the geodynamic origin of the Jurassic ophiolites in the
first place and its connection with mid-Mesozoic Cimmerian orogenic events (Neocimmerian stage). Thus, the
Triassic – Jurassic(Lower Cretaceous) Inner Dinaride Ophiolite belt is particularly interesting accounting for the
absence of the latest Jurassic – earliest Cretacous stratigraphic interval. Many of the bauxite ores are produced on
Middle Triassic to Jurassic parental limestones, whereby the hiatus can last until the beginning of the Upper
Cretaceous.
The Triassic rifting and opening of “Dinaric Tethys”, which likely caused the pre-Neocimmerian Late Triassic
shoulder uplift of early passive margins, continued into the Jurassic mid-oceanic spreading. The Triassic and
Jurassic-aged zircon grains in bauxites, including new data extracted from the bauxite geochemical database,
corroborate a volcanic parental affinity originating from exposed Jurassic volcanic rocks. The new geochemical
analysis allowed the separation of ultramafic from mafic bauxite sources, whereby acidic sources are absent or
well hidden within Inner Dinarides. Bauxite deposits at the southern edge of the Inner Dinaride area show an
abundance of incompatible Mn, demonstrating a significant transgressional Oxfordian eustatic high-stand
episode (precipitation of Mn on top of submerged paleokarst/bauxites). This, a Red Sea-type small ocean
basin with a NE-vergent suprasubduction (“Dinaric Tethys”), lasted until the end of the Jurassic (also dated by
metamorphic imprints). The tectonic exhumation processes of Inner Dinaride ophiolites involving the Neocimmerian
compressive event caused the widespread uplift episode in the latest Jurassic – earliest Cretaceous,
occasionally lasting until the Albian (Austrian unconformity). As a result, mid-Mesozoic long-lasting hiatuses
allowed intense weathering of numerous uplifted parental limestone sites, frequently producing at least two cycles of laterites and bauxite ores. The Neocimmerian episode includes the limited length (shorter cross- lithospheric across-strike width) of the latest Jurassic ophiolite obduction on top of abutting continental crust, inclusive of the onset of Lower Cretaceous Vranduk turbidites (another marker of the closing “Dinaric Tethys”)
Geochemical evaluation of dolostone deposits in Montenegro: Implications for potential industrial applications
No full textDolomite is a valuable mineral commodity with numerous industrial applications. Dolostones are mineral resources with significant growth potential. The study area encompasses south and central Montenegro. Mineralogical, petrographic, geochemical, and technological properties were investigated. Upper Cretaceous dolostones are compact and contain organic matter, whereas Triassic dolostones are weathered dolomites without organic matter. Both of formations displayed varying dolostone quality, prompting the geological and technological classification of Montenegrin dolostones. Upper Cretaceous dolostones are utilized in the building industry as aggregate, dimension stone, and filler, whereas Triassic dolomites are not suitable as dimension stone and have limited potential as aggregate. Both dolostones can be utilized in the steel industry and agriculture, but not as high-quality fillers when whiteness is a limitation, or for lime production where chemical composition and grain size are regulated. This is the first comprehensive study of geochemical evaluations of dolostone deposits in the Balkans and their potential industrial use
Graphene oxide-modified cementitious composite materials
No full textGiven that cement composites, which include cement and mortar, are currently the most extensively used building materials, their strength and durability are exceptionally important. Recent developments in unique nanoscale fibers, such as graphene oxide and carbon nanotubes, have created new avenues for improving the performance of cement composites. Graphene oxide is a two-dimensional planar sheet of compressed carbon atoms in a honeycomb structure that is a sp2-hybridized single-atomic-thick carbon allotropic building block (thickness 0.335 nm). With its unique features and enhanced performance, graphene oxide is a promising nanomaterial. Because of its exceptional mechanical, optical, thermal, and transport characteristics, it has drawn attention worldwide. Customizing the properties of cementitious composites using graphene oxide nanomaterials enhances their mechanical performance, durability, self-healing, and other multifunctional qualities, in addition to controlling the secondary hydration mechanism. The outstanding and unique performance of GO is demonstrated by its ability to increase gel pores, decrease bigger capillary pores, bridge microcracks and prevent their propagation, and improve the overall performance of cement composites. This study presents a substantial investigation of the functioning of cement composites reinforced with graphene oxide nanomaterials. Four composites have been prepared based on different cement types: ordinary Portland cement, CEM III, alumina cement, and high alumina cement. Graphene oxide was added in quantities of 2, 4, and 6 wt.%. Hydration routes were analyzed by differential thermal calorimetry. Potential changes in mineral phase composition were investigated by means of X-ray diffraction analysis. Alternations of the microstructure have been assessed by scanning electron microscopy.http://www.serbianceramicsociety.r
Cavitation resistance of refractory coatings
No full textIn this study, the resistance to the cavitation effect of three types of refractory samples based on talc with the addition of 10%, 15% and 20% cordierite was investigated. Talc has a fine structure, low hygroscopicity, insensitivity to temperature changes, low coefficient of thermal conductivity, low coefficient of linear thermal expansion, great ability to stick and coat surfaces, good grindability, low hardness. Cordierite has high refractoriness, high hardness, high density, low value of dielectric constant, low coefficient of thermal conductivity, low coefficient of linear thermal expansion, high resistance to thermal shock, relatively high melting temperature with the possibility of application up to 1380°C, high inertness towards liquid metal. Cordierite was added in order to improve properties, primarily to increase resistance to the effect of cavitation. The prepared mixtures of refractory powders were pressed under a pressure of 1 MPa and sintered at 1200°C.To evaluate the cavitation resistance properties of the investigated refractory samples, the ultrasonic vibration method with a stationary sample was applied. The change in the mass of the samples as a function of the cavitation time was monitored and the cavitation speed was determined. The formation and development of damage to the surface of the samples was monitored using a scanning electron microscope. The mechanism of degradation and resistance to the effect of cavitation of the tested samples was monitored by measuring the mass loss and morphological analysis of the pits formed on the surface of the tested samples. Research has shown that the addition of cordierite in the composition of the tested samples based on talc significantly improves the properties of resistance to the effect of cavitation.http://www.serbianceramicsociety.r
Raw clays in the production of ceramic and refractory tiles
Get PDFRaw clay samples from Serbia, mainly of kaolinitic, illitic and mixed nature, were
tested for their possible application in the production of ceramics. Using various triaxial
diagrams, the samples were sorted according to their chemical and bulk mineralogical
makeup, and also particle size distribution to determine whether they could be
employed in the production of ceramics and refractories. The areas in the ternary graphs
determined in earlier studies concerning the expected color after firing and the
applicability of the raw clays are checked and extended. The samples' water absorption
and flexural strength were assessed using EN standard procedures after they had been
hydraulically semi-dry pressed and fired at several peak temperatures between 1100
and 1300 °C. A novel triaxial diagram considering the position of the samples based on
firing temperature, water absorption and modulus of rupture is proposed, and the areas
of different kinds of ceramic tiles are defined. It is discovered that the different raw
clays can be utilized to create refractory, as well as wall and floor tiles. This study
supports the rational use of natural sources of raw materials
Evaluation of the behavior of welded structures under low-cycle fatigue loading
Get PDFWelded structures are exposed to constant variable loads during their exploitation in real conditions. A variable load affects the
integrity and life of a welded structure; therefore, it is of practical importance to understand fatigue behavior, especially the behavior
of welded structures under the impact of low-cycle fatigue. The effect of low-cycle fatigue is very prevalent in structures
and an assessment of cyclic loading of a material entails modifications of its properties and characteristics related to the dependence
of stress and strain. Since the stress-strain response during low-cycle fatigue is in the form of a hysteresis loop, this paper
presents the application of one of the two most common relations for testing resistance to low-cycle fatigue, the
Ramberg-Osgood relation, which is used to evaluate the behavior of a material, in this case a high-strength low-alloy steel
welded joint
Prošireni pristup za određivanje efekta veličine čestica na rezultate energetski disperzivne rendgenske fluorescencije za vatrostalne materijale na bazi aluminijuma
No full textKORISNIK TEHNIČKOG REŠENJA: Institut za ispitivanje materijala IMS a.d.iz Beograda
Odobreno od stane NITRA (Matični naučni odbor za materijale i hemijske tehnologije). 19.08.2024. god
Kreiranje ciljnih karakteristika drvno-plastičnih kompozita (WPC)
No full textDrvno-plastični kompoziti (WPC) predstavljaju savremene materijale sa ekspanzijom primene. U
pogledu odnosa kvalitet/troškovi, WPC su se pokazali kao izuzetno kvalitetni na tržištu u odnosu na
druge materijale istih ili sličnih namena. U kreiranju ciljnih karakteristika WPC proizvoda polazi se od
vrste komponenata, njihove interakcije i primenjene matrice. U ovom radu akcenat je bio na mehaničkim
i fizičkim karakteristikama, koje zbog značaja često predstavljaju osnov istraživanja. Dat je uvid u
aktuelno stanje – korišćenje WPC proizvoda, pregled odabranih uticaja važnih za proces kreiranja
ciljnih karakteristika WPC, odabrani savremeni primeri kreiranja ciljnih karakteristika, kao i primer
studije osnovnih fizičkih karakteristika WPC na grupi proizvoda (sinergija parametara)