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1.
The action of a laser on an aluminium target
Višnja Henč-Bartolič, Tonica Bončina, Suzana Jakovljević, Davor Pipić, Franc Zupanič, izvirni znanstveni članek

Opis: A nitrogen laser beam (337 nm, 6 ns (FWHM), (3.2 [plus minus] 0.2) mJ) was focused with a quartz lens (f = 100 mm) onto an aluminium target in air at normal pressure. The laser irradiation and plasma explosion caused a modification to the Al surface and the deposition of a thin film (droplets) onto a glassy carbon plate. The irradiated target and the deposited material were studied with a scanning electron microscope (SEM) and a focused-ion-beam (FIB) device. A crater surrounded by a rim was produced on the spot of maximum irradiation on the aluminium target. The crater, very deep in comparison to its width and thickness, was presumably caused by the Kelvin-Helmholtz and the Rayleigh-Taylor instabilities. The temperatures of the electron and the massive particles were explained.
Ključne besede: aluminium, laser ablation, thin film deposition, instabilities, temperatures
Objavljeno: 23.03.2017; Ogledov: 23; Prenosov: 0
.pdf Polno besedilo (324,07 KB)

2.
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, 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: 26; Prenosov: 0
.pdf Polno besedilo (1,13 MB)

3.
Synthesis of micro-composite beads with magnetic nano-particles embedded in porous CaCO[sub]3 matrix
Alenka Vesel, Aljoša Košak, David Haložan, Kristina Eleršič, 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: 22; Prenosov: 0
.pdf Polno besedilo (429,86 KB)

4.
Superplastic deformation of an X7093 Al alloy
Srdjan Tadić, Aleksandar Sedmak, Radica Prokić-Cvetković, Abdsalam Eramah, Rebeka Rudolf, 2014, izvirni znanstveni članek

Opis: We have investigated the superplastic deformation mechanism of a powder-metallurgy, high-zinc X7093 Al alloy. The objective was to examine the rate-controlling mechanisms that govern its superplastic deformation. The investigations were carried out in the temperature range 490–524 °C and strain rates of 4.17 × 10–5 s–1 to 2.1 × 10–2 s–1. The maximum ductility was slightly more than 500 % at 524 °C and 4.2 × 10–4 s–1. The values of the stress exponent (n) and the activation energy (Q) indicated that the deformation is rate-controlled by the climb within the grain-boundary diffusion path. The existence of a temperature-dependent threshold stress was confirmed.
Ključne besede: superplasticity, Al alloys, deformation mechanisms
Objavljeno: 23.03.2017; Ogledov: 13; Prenosov: 0
.pdf Polno besedilo (580,64 KB)

5.
Numerična analiza vpliva turbulentnega toka na obnašanje alg
Urška Žibert, 2017, magistrsko delo/naloga

Opis: O obnašanju alg v turbulentnem toku še ni bilo narejenih veliko raziskav, vendar ima njihovo proučevanje vedno večji pomen zaradi škodljivosti cvetenj na okolje. Pričujoča raziskava je bila usmerjena v raziskavo obnašanja alg v turbulentnem toku in kvantifikacijo rezultatov s statističnimi orodji. Uporabljena metoda dela je bila numerični model Vreteno DNS, ki se je do sedaj uporabljal le za nežive delce. Za posamezne primere simulacije sta bili izbrani algi Microcystis flos-aquae in Planktothrix rubescens. Obravnavali smo tri primere: posamezne celice okroglih alg Microcystis flos-aquae, kolonije po 100 celic alg Microcystis flos-aquae in paličaste alge Planktothrix rubescens. Alge so bile modelirane kot togi delci s sferično obliko oziroma aproksimirane z elipsoidom. Alge smo modelirali v turbulentnem toku v kanalu, kjer je bilo strižno Reynoldsovo število 〖Re〗_τ = 150, ki se nanaša na polovično višino h in strižno hitrost u_τ. Strižna hitrost u_τ, ki temelji na povprečni strižni napetosti na steni in gostoti tekočine, je bila enaka 0,505 m/s. Polovična višina h pa je znašala 0,3 mm. Predstavljeni rezultati so na prvi pogled pri vseh treh primerih zelo podobni. Najbolj očitna podobnost med njimi je zadrževanje ob robovih kanala. Alge v sredini toka imajo najvišje hitrosti, če gledamo globinsko-hitrostne profile primerov. Hitrostni profili alg so precej podobni. Največ alg ima v vseh treh primerih hitrosti med 15 in 18 m/s. Rezultati, ki so med seboj tako podobni, dajejo slutiti, da pri algah bolj kot velikost in oblika na razporeditev v toku vpliva gostota, ki ima pri algah vrednosti, ki se med seboj ne razlikujejo veliko. Do večjih razlik med primeri bi lahko prišlo tudi pri povečanju Re-števila, kar pomeni bolj turbulentni tok, ki bi imel večji vpliv na alge.
Ključne besede: matematično-fizikalni model, Vreteno DNS, alge, turbulentni tok
Objavljeno: 23.03.2017; Ogledov: 12; Prenosov: 3
.pdf Polno besedilo (3,09 MB)

6.
Razvoj modela za tvorbo in razpad kolonij sferičnih alg v toku vode
Andraž Najžar, 2017, magistrsko delo/naloga

Opis: Do sedaj se je numerični model Vreteno DNS uporabljal zgolj za nežive delce. V magistrski nalogi pa smo se osredotočili na vedenje živih organizmov, alg. Prav tako Vreteno DNS do sedaj ni imelo vgrajenega modula za določanje trkov med delci. Ta raziskava je usmerjena v nadgradnjo sedanjega modela, da bo le-ta uporaben tudi za žive organizme ter bo upošteval trke, do katerih nedvomno prihaja v turbulentnem toku. Za izhodišče smo izbrali model trdih sfer, iz katerega smo pridobili enačbe za smer in hitrost, v_1 in v_2, ter kotni hitrosti, ω_1 in ω_2, alg po trku. Nato smo določili še smer in hitrost gibanja morebitne novonastale kolonije alg v_3, kakor tudi njeno kotno hitrost ω_3. Sedaj smo postavili pogoj, ki pogojuje trke z medsebojno razdaljo alg v času trkov. Razdaljo smo označili s črko B. Določili smo, da se bo trk zgodil, kadar bo B večji kot 0 in kadar bo manjši kot vsota polmerov obeh alg. V naslednjem koraku smo poiskali še ustrezen biološki parameter, ki določa, kdaj se alge med seboj odbijajo in kdaj prihaja do združevanja alg v kolonije. Ta parameter je stopnja hidrofobnosti ∆G. V primeru negativne stopnje hidrofobnosti prihaja do nastanka kolonij, medtem ko se v primeru pozitivne stopnje hidrofobnosti kolonije ne tvorijo, pač pa se alge med seboj odbijajo. Vse parametre in enačbe smo nato vstavili v program Scilab in nato še v model Vreteno DNS. Zagnali smo tri simulacije, in sicer simulacijo brez trkov, simulacijo s trki z odboji in še simulacijo, kjer se alge združujejo v kolonije. Podatke za simulacije smo pridobili iz magistrske naloge U. Žibert, ki je nastajala vzporedno s to nalogo. Rezultate smo nato med seboj grafično primerjali in ugotavljali vplive, ki jih imajo trki na vedenje alg. Ugotovili smo, da le-ti imajo nedvomen vpliv in jih model mora upoštevati, če se želimo kar se da približati naravnemu stanju.
Ključne besede: trki, združevanje v kolonije, alge, Vreteno DNS, model trdih sfer
Objavljeno: 23.03.2017; Ogledov: 10; Prenosov: 1
.pdf Polno besedilo (3,48 MB)

7.
Processing poly(ether etherketone) an a 3D printer for thermoplastic modelling
Bogdan Valentan, Žiga Kadivnik, Tomaž Brajlih, Andy Anderson, Igor Drstvenšek, 2013, izvirni znanstveni članek

Opis: PEEK, poly(ether etherketone), is one of the high-quality industrial polymers. It is widely used in extremely demanding areas like automotive, aircraft and space industries. Because of the fact that it is bio-compatible, PEEK is also used for medical implants that are usually made by milling a block of the material. The article presents the results of an investigation of processing PEEK on a 3D printer for thermoplastic modelling. The used procedure is one of the additive manufacturing procedures and, as such, it builds a product by adding material layer by layer to get the finished product. Commercially available machines are unable to achieve the required melting and environment temperatures, so a new machine was developed. The machine was designed and built at the company Ortotip d.o.o. and it is able to produce the parts of up to 130 mm Ž 130 mm Ž 150 mm. After the initial testing, test specimens, according to standards EN ISO 527-2: 2012 and EN ISO 178: 2011, were produced and tested at the facilities of the PEEK manufacturer Invibio (from the UK). The article presents the steps taken when developing the PEEK modelling machine, the test methods to verify the mechanical properties of manufactured products and the results of the material testing. The machine was developed to produce medical implants (specific maxillofacial prosthesis), but with additional testing (that will help to improve the mechanical properties of produced parts) practically all bone-replacement implants can be made.
Ključne besede: PEEK, 3D printer, implant, medical application, thermoplastic, FDM, biocompatible, additive technology
Objavljeno: 17.03.2017; Ogledov: 44; Prenosov: 0
.pdf Polno besedilo (2,10 MB)

8.
Pressing of partially oxide-dispersion-strengthened Copper using the ECAP process
Matija Kos, Janko Ferčec, Mihael Brunčko, Rebeka Rudolf, Ivan Anžel, 2014, izvirni znanstveni članek

Opis: A combination of internal oxidation (IO) and equal channel angular pressing (ECAP) was used to explore the possibility of uniting the mechanisms of dispersion and deformation strengthening to improve the properties of a Cu-Al alloy with 0.4 % Al. The IO of Cu-Al billets served in the first step of the experiment as a means for dispersion, strengthening the mantle of the billets with a fine dispersion of nanosized oxide particles. The experimental procedure continued with deformation strengthening performed by ECAP, which allowed an intense plastic strain through simple shear. Material flow in a partly internally oxidized Cu-0.4 % Al billet and in a homogenous reference sample made of modelling mass was also studied to analyse, on the macroscale, the influence of the internal oxidation zone (IOZ) on the material flow behaviour during the ECAP process. The analysis was performed with the aim of revealing the uniformity of the strain distribution and to obtain information about the deformation strengthening across the volume of the billet. We found that the oxide particles have a minor influence on the material flow on the macroscopic scale during the ECAP process. However, the degree of deformation strengthening in the IOZ was much lower than in the unoxidized core region. The combination of IO and ECAP allows us to produce a Cu composite composed of a hardened oxidized mantle region with good electrical and thermal conductivity and a high- hardened core region. This combination represents a new technological route for the production of high-hardness Cu composites, which could also be used at higher temperatures.
Ključne besede: ECAP, Cu-Al alloys, strengthening mechanisms, internal oxidation
Objavljeno: 17.03.2017; Ogledov: 43; Prenosov: 0
.pdf Polno besedilo (955,64 KB)

9.
Neutralization of waste filter dust with CO[sub]2
Lidija Fras, Ivan Anžel, Andrej Stergaršek, Ana Kračun, 2015, strokovni članek

Opis: In this paper we report on the possibility of neutralizing filter dust from Talum Livarna d.o.o. The filter dust that remains after cleaning flue gas with the classification number of waste 10 10 09* is alkaline and contains heavy metals, non-metals, organic pollutants, and, therefore, has the properties of hazardous waste. The possibility of neutralizing this dust with CO2 was studied. The results showed that the treatment successfully lowered the pH value between the limits 6 and 9, which is within the legal constraints of pollution for strong acidic or alkaline waste. The contents of the hazardous substances were lowered, i.e., As, Cu, Ba, Zn, Cd, Cr, Ni, Pb, Sn, Mn and V, with percolation values that are below the level of the prescribed threshold-limit values for substances that allows their disposal in non-hazardous waste landfills. Only the percolation values of Sb, Cd, Mo and Se exceed the prescribed threshold limit values of substances that allow their disposal in inert waste landfills. The XRD analysis after the neutralization of the filter dust using CO2 showed no presence of CaO. The neutralized filter dust can be land filled as a stabilized and unreactive waste in landfills for nonhazardous wastes. Their properties also offer the possibility for incorporating them into some other material or product, such as the production of new composite materials, their use in construction products and perhaps cements or usage in backfills.
Ključne besede: hazardous waste, filter dust, neutralization, stabilization, chemical properties
Objavljeno: 17.03.2017; Ogledov: 24; Prenosov: 0
.pdf Polno besedilo (438,33 KB)

10.
Morphology and corrosion properties PVD Cr-N coatings deposited on aluminium alloys
Darja Kek-Merl, Ingrid Milošev, Peter Panjan, Franc Zupanič, 2011, izvirni znanstveni članek

Opis: The attempt to find an alternative coating for corrosion protection of Al- alloys was made. PVD coatings are one of the possible alternatives for replacement of ecological unfriendly chromate coatings. Chromium-nitride (Cr-N) and Ni/Cr-N coatings were sputtered on aluminium substrates (AA7075 and cladded AA2024). Surface and sub-surface characterizations were performed by AFM and SEM. Special attention was given to defects incorporated into coatings, since they play important role in the corrosion protection of the coating/substrate systems. The cross-sections through the typical defects were performed by ion beam milling incorporated into the SEM. The Vickers hardness of the Cr-N with and without layer of Ni on both substrates was determined. After the coatings deposition, the values of Vickers hardness (10 mN load) increase for 10 to 100-fold compared to the substrates. The corrosion behaviour of Cr-N and Ni/Cr-N thin films was investigated in near neutral 0.1 M solution of NaCl using potentiodynamics electrochemical measurement. Cr-N and Ni/Cr-N coatings shift the corrosion potentials to more positive values. The best corrosion resistance among the tested coating/substrate systems were found for Ni/Cr-N on AA7075 substrate.
Ključne besede: Al-alloys, corrosion properties, CrN films, FIB, PVD coatings
Objavljeno: 17.03.2017; Ogledov: 23; Prenosov: 0
.pdf Polno besedilo (735,62 KB)

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