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Peter Fajs, 2019, magistrsko delo

Opis: The objective of the master thesis is to determine the filling properties of injection moulding process for newly created material, and to understand how the variation of processing parameters affects the flow possibilities. In thesis two materials were analysed, i.e. neat PLA material, which was used as a benchmark material and newly created composite CitrusPLA that is based on biodegradable PLA matrix and reinforced with citrus fibres. To fulfil the aim, the virtual and experimental design of experiment with the Taguchi methodology was conducted with use of spiral flow test, where the flow length of material through mould cavity was observed. The experimental results were the basis for the accuracy validation of numerical results and also to determine the optimum process parameters for injection moulding products with best flow conditions through statistical evaluation. It has been concluded that the newly created composite has lower viscosity compared to benchmark virgin PLA which results in better flow conditions in spiral flow test analysis. Both materials have the same optimal conditions in terms of flow conditions. The contribution of mould temperature is in both cases negligible. However, other two variated parameters i.e. melt temperature and injection speed have higher influence on filling characteristics for both materials.
Ključne besede: injection moulding optimization, material characterization, Moldflow, injection moulding simulations, Taguchi DOE, bio-composites, citrus waste fibres, PLA
Objavljeno: 07.06.2019; Ogledov: 608; Prenosov: 0

Investigations to establish the influence of the thermal energy field on soil properties
Srinivas Kadali, Susha Lekshmi, Susmita Sharma, D. N. Singh, 2013, izvirni znanstveni članek

Opis: This paper describes details of a study to investigate and demonstrate the changes undergone by soil when it is exposed to elevated temperatures. Such situations are commonly encountered while designing the foundations for the furnaces, boiler units, forging units, brick kilns, rocket launching pads, buried power-supply cables, air-conditioning ducts, underground explosions, disposal of high-level radioactive and industrial toxic wastes, ground modifications or soil-stabilization techniques, etc. As such, investigations to establish changes undergone by the soil when it is exposed to elevated temperatures assume some importance. With this in view, individual samples of six soils, with entirely different characteristics, were subjected to temperatures up to 300°C (sequentially in steps of 50°C) and after each step of thermal treatment, these samples were characterized for their physical, chemical and mineralogical properties. Based on a critical synthesis of the results, it has been demonstrated that elevated temperatures cause (i) a change in the color, (ii) an increase in the specific gravity, particle size and weight loss, (iii) a reduction in the specific surface area, cation-exchange capacity and zeta-potential, and (iv) a structural transformation of the soil. Though these changes would affect the engineering properties of the soil to a large extent, the scope of this paper is limited to demonstrating the alterations in physical, chemical and mineralogical changes, only, occurring in the soil when it is exposed to elevated temperatures.
Ključne besede: elevated temperatures, soil, characterization, physical characteristics, chemical characteristics, mineralogical characteristics
Objavljeno: 14.06.2018; Ogledov: 457; Prenosov: 27
.pdf Celotno besedilo (1,08 MB)
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Synthesis, crystal structure and magnetic properties of a new hydroxylammonium fluoroferrate
Brina Dojer, Matjaž Kristl, Zvonko Jagličić, Amalija Golobič, Marta Kasunič, Mihael Drofenik, 2012, izvirni znanstveni članek

Opis: This paper reports on the synthesis of a new hydroxylammonium fluoroferrate, with the formula $(NH_3OH)_3FeF_6$, obtained after dissolving iron powder in hydrofluoric acid and adding solid $NH_3OHF$. This new compound has been characterized by chemical and thermal analysis, single-crystal X-ray diffraction, and magnetic measurements. The title compound crystallizes trigonal, R3c, with cell parameters a = 11.4154(2) Å, c = 11.5720(2) Å, Z = 6. The structure consists of $NH_3OH^+$ cations and isolated $FeF_6^{3–}$ octahedra in which the central ion lies on a threefold axis. The oxygen and nitrogen atoms of the hydroxylammonium cations are donors of hydrogen bonds to fluoride anions, resulting in a network of hydrogen bonds between counterions. The effective magnetic moment $µ_{eff}$ = 5.8 BM was calculated and perfectly matches the expected value of high-spin Fe(III) ions. The thermal decomposition of the compound was studied by TG, DSC, and X-ray powder diffraction.
Ključne besede: inorganic chemistry, crystallography, coordination compounds, synthesis, crystal structure, characterization of compounds, determination of the structure of compounds, X-ray diffraction, magnetic measurements, thermal analysis, TG, DSC, hydrogen bond, metal complexes, hydroxylammonium fluoromethalatehydroxylammonium, fluoroferrate
Objavljeno: 25.08.2017; Ogledov: 1015; Prenosov: 50
.pdf Celotno besedilo (198,42 KB)
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Synthesis and characterisation of hydroxylammonium fluorochromate
Matjaž Kristl, Mihael Drofenik, Ljubo Golič, Amalija Golobič, 2003, izvirni znanstveni članek

Opis: Reactions in the system $Cr – NH_3OHF – HF – H_2O$ were investigated. Green crystals of a new compound with the formula $(NH_3OH)_3CrF_6$ have been isolated from the water solution and characterized by chemical analysis. The compound crystallizes as triclinic, P-1, with cell parameters: a = 6.5461(2) Å, b = 6.9347(2) Å, c = 9.4072(3) Å, α = 86.772(1)°, β = 83.804(1)°, γ = 70.283(1)°. The effective magnetic moment, $µ_{eff}$ = 3.82 BM, was calculated from magnetic susceptibility measurements in the temperature range 80-290 K. The thermal decomposition of the compound was studied by TG and DSC analysis. $(NH_3OH)_3CrF_6$ decomposes above 125 °C in three steps and the residue has been identified by X-ray powder diffraction as $α – Cr_2O_3$.
Ključne besede: inorganic chemistry, structural chemistry, crystalline structure, coordination compounds, synthesis, inorganic reactions, thermal decomposition, characterization of compounds, TG, DSC, X-ray diffraction, chromium complexes, hydroxylammonium fluoro chromates, crystals
Objavljeno: 25.08.2017; Ogledov: 867; Prenosov: 76
.pdf Celotno besedilo (206,45 KB)
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A new characterization and a recognition algorithm of Lucas cubes
Andrej Taranenko, 2013, izvirni znanstveni članek

Opis: Fibonacci and Lucas cubes are induced subgraphs of hypercubes obtained by excluding certain binary strings from the vertex set. They appear as models for interconnection networks, as well as in chemistry. We derive a characterization of Lucas cubes that is based on a peripheral expansion of a unique convex subgraph of an appropriate Fibonacci cube.This serves as the foundation for a recognition algorithm of Lucas cubes that runs in linear time.
Ključne besede: graph theory, Lucas cubes, characterization, recognition algorithm
Objavljeno: 10.07.2017; Ogledov: 577; Prenosov: 67
.pdf Celotno besedilo (563,10 KB)
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Mechanical properties and microstructure characterisation of Au-Pt dental alloy
Rebeka Rudolf, Tjaša Zupančič Hartner, Ladislav Kosec, Aleksandar Todorović, Borut Kosec, Ivan Anžel, 2008, izvirni znanstveni članek

Opis: Development of a dental alloy with high Au content is based on the ternary system of Au-Pt-Zn with a nominal composition of 86,9Au-9,9Pt-1,5Zn, and about 1,5 wt.% micro-alloying elements (In, Ir, Rh). The results analyses of different heat-treated states showed that the optimal mechanical properties and hardness of an Au-Pt-Zn alloy can be reached with combinations of heat treatment for 20 minutes at 723 K and then slowly cooling, if the alloy was annealed at 1223 K for 30 minutes and the water quenched. Research results confirmed that the microstructure of the Au-Pt-Zn alloy consists of two phases: α1-phase rich in Au (main phase) and α2-phase rich in Pt (minor phase). During XRD analysis and use of the Rietveld method, it was found that the α1-phase content is about 98,5 wt.% while the content of α2-phase is 1,5 wt.%. STA analyses show that the Au-Pt-Zn alloy has a solidus temperature of about 1292 K and a liquidus temperature of about 1412 K.
Ključne besede: Au dental alloy, properties, microstructure, characterization
Objavljeno: 03.07.2017; Ogledov: 615; Prenosov: 73
.pdf Celotno besedilo (1,59 MB)
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Synthesis of NiTi/Ni-TiO[sub]2 composite nanoparticles via ultrasonic spray pyrolysis
Peter Majerič, Rebeka Rudolf, Ivan Anžel, Jelena Bogovic, Srečko Stopić, Bernd Friedrich, 2015, izvirni znanstveni članek

Opis: In this paper we present the production of NiTi/Ni-TiO2 composite nanoparticles via the synthesis method called ultrasonic spray pyrolysis (USP). The precursor solution for the synthesis of spherical NiTi particles was prepared from an orthodontic wire with a chemical composition of Ni (amount fraction x = 51.46 %) and Ti (x = 48.54 %). TEM microscopy, in combination with EDX analyses, was used for a detailed characterization of the obtained NiTi nanoparticles. The results showed the nanoparticle sizes ranging from 60 nm to 600 nm, depending on the parameters of the production procedure. This showed the versatility of the new USP synthesis procedure, proving its usefulness for different materials and applications.
Ključne besede: ultrasonic spray pyrolysis, NiTi/Ni-TiO2 composite nanoparticles, characterization, Transmission electron microscope (TEM), TEM microscopy
Objavljeno: 23.03.2017; Ogledov: 723; Prenosov: 84
.pdf Celotno besedilo (1,13 MB)
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Synthesis of micro-composite beads with magnetic nano-particles embedded in porous CaCO[sub]3 matrix
Alenka Vesel, Aljoša Košak, David Haložan, Kristina Eleršič, 2012, izvirni znanstveni članek

Opis: A method for synthesis of soft magnetic microbeads is presented. The microbeads are made from magnetic nanoparticles dispersed in CaCO3 (calcium carbonate) matrix. The composite beads are almost perfectly spherical with a diameter of few micrometers. The majority of the composite beads consists of a porous CaCO3 matrix. Magnetic nanoparticles with a size of about 10-15 nm are made of Fe2O3. They are captured inside the pores of CaCO3 matrix during its formation. CaCO3 matrix is formed by crystallization from saturated solution of sodium carbonate and calcium chloride. The composite beads are coated with a layer of functionalized polymer. The magnetic microbeads were characterized by SEM and XPS. Different functional groups were detected by XPS measurements including SO3–,NH3+,NH2,CO32– and OH groups. The results indicate that the iron oxide particles are absent on the surface and that the polymer coating serves as a good biocompatible film.
Ključne besede: composite, surface characterization, XPS, functionalization, Fe nanoparticles, microbeads
Objavljeno: 23.03.2017; Ogledov: 608; Prenosov: 67
.pdf Celotno besedilo (429,86 KB)
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Mechanical properties of the materials for bruxoguards
Vojkan Lazić, Aleksandra Špadijer Gostović, Nebojša Romčević, Igor Đorđević, Ana Todorović, Rebeka Rudolf, 2014, izvirni znanstveni članek

Opis: The aim of this study is to investigate the mechanical properties of polymethyl methacrylate (PMMA) and thermoplastic polycarbonate (TPC) materials in order to produce night bruxoguards. For this purpose we used a static tensile test. In the next step the microstructures of PMMA and TPC were observed. Within this framework special attention was paid to the examination of the tensile-test tube fracture surfaces for both materials. This approach revealed that PMMA is a brittle and TPC is a plastic material. Certain mechanical properties and a review of the crucial areas confirmed that the TPC material is extremely favourable for making occlusal splints.
Ključne besede: polymers, mechanical properties, characterization, bruxoguards, polymethyl methacrylate, thermoplastic polycarbonate
Objavljeno: 16.03.2017; Ogledov: 770; Prenosov: 79
.pdf Celotno besedilo (348,98 KB)
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