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1.
CFD analysis of exothermic reactions in Al-Au nano multi-layered foils
Karlo Raić, Rebeka Rudolf, Primož Ternik, Zoran Žunič, Vojkan Lazić, Dragoslav Stamenković, Tatjana Tanasković, Ivan Anžel, 2011, original scientific article

Abstract: This work presents the possibility of numerical modelling using Computational Fluid Dynamics (CFD) in the field of nano-foils. The governing equations were solved using a Finite Volume Methodology (FVM). The computational domain was discretized using a uniform Cartesian grid with the appropriate mesh size along the x and y directions employing the corresponding number of grid points. The field variables were discretized at the cell centres and the spatial, as well as the time, derivatives were approximated using the second-order accurate numerical scheme. The time-evolution of the temperature and concentration fields, as well as the atomic diffusion coefficient, will be presented for the appropriate Al-Au nano-foil geometry and boundary conditions.
Keywords: Au-Al nano-foils, finite volume method, temperature transfer, concentration transfer
Published: 01.06.2012; Views: 994; Downloads: 59
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2.
Nanofoils for soldering and brazing in dental joining practice and jewellery manufacturing
Karlo Raić, Rebeka Rudolf, Borut Kosec, Ivan Anžel, Vojkan Lazić, Aleksandar Todorović, 2009, original scientific article

Abstract: This paper describes the development of novel, reactive Al-Au nano-multilayered foils, their possible application in different fields and a discussion of the nano-foils' suitability for dental and jewellery applications. Moreover, this study includes the rapid joining of similar and dissimilar materials, by placing multilayer nano-foils and two layers of solder or braze. The foils precisely control the instantaneous release of heatenergy for the joining and act as a controllable local heat source. The reactive foils' thickness is in the range 10 nm to less than 100 nm and they contain many nanoscale layers that alternate between materials with high mixing heats, such as Al and Au. The foil between the two solder/braze layers melts the solder/braze with the heat generated by the reaction and bonds the components. The use of reactive foils eliminates the need for a furnace and dramatically increases the soldering/brazing heating rate of the components being bonded. Thus, ceramics and metals can be fused over required areas without the thermal stresses that are encountered in furnace soldering or brazing. In addition, a completely new plasma technology is proposed for the manufacturing of nano-foils and the first results of the preliminary experimental testing are presented.
Keywords: ceramic-metal bonding, low-temperature, nano-foils, plasma technology, dentistry, jewellery
Published: 01.06.2012; Views: 1251; Downloads: 41
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3.
Aspects of titanium-implant surface modification at the micro and nano levels
Iva Milinković, Rebeka Rudolf, Karlo Raić, Zoran Aleksić, Vojkan Lazić, Aleksandar Todorović, Dragoslav Stamenković, 2012, original scientific article

Abstract: The shape and chemical composition, as well as the macro- and microtopography, of an implant surface have been studied widely as the major factors that positively influence implant osseointegration. Titanium and titanium alloys have been used extensively over the past 20 years as biomedical materials in orthopedic and dental surgery because of their good mechanical properties, corrosion resistance, no cell toxicity, and very poor inflammatory response in peri-implant tissue, which confirms their high biocompatibility. Their favorable biological performance is attributed to a thin native oxide film that forms spontaneously on the titanium surface. It is well established that surface roughness plays an important role in implant fixation. Accordingly, some authors have indicated the existence of an optimal range of surface roughness. The titanium surface can be either chemically or physically modified, or both, in order to improve biomaterial-tissue integration. Different treatments are used to modify the titanium surface. Hydroxyapatite coatings, preceded or not by acid etching, are used to create a rough, potentially bioactive surface. Oxide blasting treatments, either with or without chemical etching, are used to develop roughsurfaces. Thick oxide films obtained by anodic or thermal oxidation have been used to accelerate the osseointegration process. The ideal microtopography of the surface is still unknown, however, because it is very difficult to associate surface properties with clinical results. As more accurate knowledge is required, several Ti surfaces have been analyzed and the endosseous implant surface modified on the micro level has been thoroughly studied. Additionally, the production of gold (Au) nanoparticles to be added to the micron-scale modified surface has been performed. In this respect, an appropriate overview of our results is given.
Keywords: Ti implant, Au nanoparticles titan alloys, surface modification, microstructure
Published: 10.07.2015; Views: 697; Downloads: 45
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4.
Hydroxyapatite coatings on Cp-Titanium Grade-2 surfaces prepared with plasma spraying
Rebeka Rudolf, Dragoslav Stamenković, Zoran Aleksić, Monika Jenko, Igor Đorđević, Aleksandar Todorović, Vukoman Jokanović, Karlo Raić, 2015, original scientific article

Abstract: Thin hydroxyapatite coatings were produced on Cp-Titanium Grade-2 samples, with new high-voltage pulse-power equipment PJ-100 (Plasma Jet, Serbia) in order to get a more stable implant structure appropriate for further clinical applications. A comparative analysis of differently prepared surfaces of the Cp-Titanium Grade-2 samples was done before the hydroxyapatite was applied. Microstructural observation of the modified hydroxyapatite/implant surface was done using scanning-electron-microscopy imaging and Auger electron spectroscopy, with the aim of detecting the morphology and the elements contained in the new surfaces of the samples. The results confirmed that the surface of Cp-Titanium Grade-2 modified with hydroxyapatite is very similar to the bone structure.
Keywords: Cp-Ti2 material, hydroxyapatite, plasma, characterization
Published: 16.03.2017; Views: 433; Downloads: 42
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5.
Liquid metal/ceramic interfaces in dental practice and jewellery manufacturing
Karlo Raić, Rebeka Rudolf, Aleksandar Todorović, Dragoslav Stamenković, Ivan Anžel, 2010, review article

Abstract: Metal-ceramic fusing has been the essential step in obtaining materials that benefit from both ceramic and metal constituents, i.e. where the combined properties of metal and ceramic layers are desirable. When considering fusing methods, soldering and active metal brazing are the most effective. These processes involve braze melting and flowing between the two pieces of material. In the first part the phenomena occurring on the boundary between the ceramics and the active filler metal during the metal-ceramics joining are discussed. Three interconnected sub-processes are considered: (1) wetting of the ceramic surface, (2) chemical reactions at the interface and (3) diffusion with a moving interface. Then, the appearances at the grain boundary grooves of the ceramic surface are presented as phenomena on the catalytic surface. In the second part, examples from dental practice and jewellery manufacturing are used for comparative analysis. Finally, we discuss the composition and properties of the soldering and brazing alloys used for dental practice and jewellery manufacturing.
Keywords: metal-ceramic bonding, brazing, soldering, dentistry, jewellery
Published: 10.07.2015; Views: 547; Downloads: 43
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