SLO | ENG

Večja pisava | Manjša pisava

Iskanje po katalogu digitalne knjižnice Pomoč

Iskalni niz: išči po
išči po
išči po
išči po
* po starem in bolonjskem študiju

Opcije:
  Ponastavi


Iskanje brez iskalnega niza vrača največ 100 zadetkov!

1 - 10 / 100
Na začetekNa prejšnjo stran12345678910Na naslednjo stranNa konec
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 nanocrystalline nickel-zinc ferrites within reverse micelles
Vuk Uskoković, Mihael Drofenik, izvirni znanstveni članek

Opis: Nanocrystalline nickel-zinc ferrites were synthesized via a reverse micelle microemulsion route. The precursor cations were precipitated in the microemulsion system CTAB/1-hexanol/water. A subsequent oxidizing reaction was used to synthesize the nickel-zinc ferrite. The obtained nanoparticles were less than 20 nm in size.
Ključne besede: nanomaterials, ferrite, powders synthesis, microemulsion, reverse micelle
Objavljeno: 23.03.2017; Ogledov: 21; Prenosov: 0
.pdf Polno besedilo (109,33 KB)

4.
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)

5.
Sinteza magnetnih nanodelcev, funkcionaliziranih s tanko plastjo silike
Stanislav Čampelj, Darko Makovec, Marjan Bele, Mihael Drofenik, Janko Jamnik, izvirni znanstveni članek

Opis: V prispevku opisujemo pripravo maghemitnih nanodelcev prevlečenih s siliko. Postopek je potekal v treh ločenih stopnjah. V prvi smo delce sintetizirali s koprecipitacijo ionov Fe[na]{2+} in Fe[na]{3+}. V drugi smo delce prevlekli s citronsko kislino, da bi preprečili aglomeracijo, in jih dispergirali v vodi. Uspešnost dispergiranja smo spremljali z ugotavljanjem masnega deleža delcev, dispergiranih v vodi. Vsebnost delcev je odvisna od pH-vrednosti pri kateri secitronska kislina adsorbira na površini in koncentracije raztopljene citronske kisline. Tretja stopnja postopka je vsebovala prevlačenje nanodelcev s siliko, ki je potekalo v vodni suspenziji. Ključnega pomena za uspešno prevlačenje nanodelcev s siliko je stabilnost suspenzije nanodelcev oblečenih s citronsko kislino.
Ključne besede: maghemit, nanodelci, citronska kislina, silika, vodna suspenzija
Objavljeno: 23.03.2017; Ogledov: 19; Prenosov: 0
.pdf Polno besedilo (731,75 KB)

6.
Synthesis comparison and characterization of chitosan-coated magnetic nanoparticles prepared with different methods
Gordana Hojnik Podrepšek, Željko Knez, Maja Habulin, 2014, izvirni znanstveni članek

Opis: In this study, magnetic maghemite nanoparticles were prepared with the coprecipitation method, due to its simplicity and productivity. Thereafter, chitosan-coated magnetic nanoparticles were synthesized with three different methods, the micro-emulsion process, the suspension cross-linking technique and the covalent binding. Subsequently, a comparison of the used methods was done using various analyses such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetry (TGA), differential scanning calorimetry (DSC), vibrating-sample magnetometry (VSM) and dynamic light scattering (DLS). The characterization results from Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) indicated a successful binding of chitosan on the magnetic nanoparticles. SEM pictures showed that spherical structured particles with an increased particle size were obtained as the chitosan layer around the particles was increased. Considering that the magnetic-separation technique has the advantages of rapidity, high efficiency, cost-effectiveness and lack of negative effect on the biological activity, these carriers may be applied in enzyme immobilization.
Ključne besede: magnetic nanoparticles, chitosan, surface functionalization
Objavljeno: 23.03.2017; Ogledov: 18; Prenosov: 0
.pdf Polno besedilo (1022,83 KB)

7.
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)

8.
Efekt PTKU v močno donorsko dopirani keramiki BaTiO[spodaj]3
Nina Ule, Darko Makovec, Mihael Drofenik, 2000, izvirni znanstveni članek

Opis: Navadno izdelujejo upore s pozitivnim temperaturnim koeficientom upornosti (PTK-upore) s sintranjem nizko donorsko dopiranega BaTiO3 na zraku. Koncentracija donorja ne sme preseči kritične velikosti (-0,3 mol.% med sintranjem na zraku), ki povzroči zaustavitev pretirane rasti zrn med sintranjem. S sintranjem v redukcijski atmosferi lahko povišamo kritično koncentracijo donorja, in tako dobimo močno donorsko dopiran BaTiO3 z grobo zrnato mikrostrukturo. V grobo zrnatem BaTiO3 lahko s poznejšo reoksidacijo z žganjem na zraku uravnavamo PTKU-efekt. V tem delu so predstavljeni rezultati raziskave PTKU-efekta v keramikah BaTiO3, dopiranih s koncentracijami La od o do 20 ml.%. Vzorci so bili sintrani v redukcijski mešanici N2 z 1 % H2 in pozneje reoksidirani z žganjem na zraku.
Ključne besede: polprevodni BaTiO3, donorsko dopiranje, električne lastnosti, PTKU-efekt, mikrostruktura
Objavljeno: 17.03.2017; Ogledov: 47; Prenosov: 1
.pdf Polno besedilo (344,81 KB)

9.
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)

10.
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)

Iskanje izvedeno v 1.05 sek.
Na vrh
Logotipi partnerjev Univerza v Mariboru Univerza v Ljubljani Univerza na Primorskem Univerza v Novi Gorici