| | SLO | ENG | Piškotki in zasebnost

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


1 - 9 / 9
Na začetekNa prejšnjo stran1Na naslednjo stranNa konec
Membranes from polysulfone/N,N-dimethylacetamide/water system : structure and water flux
Vladimir Kaiser, Črtomir Stropnik, 2000, izvirni znanstveni članek

Opis: Polymeric membranes were prepared by the wet-phase separation method from solutions of different contents of polysulfone in N,N-dimethylacetamide; solutions were cast in different thickness before immersion into the pure water coagulation bath. Two main processes take place during the formation of membranes: nucleation and growth of the polymer lean phase with subsequent solidification of the polymer rich phase, and the formation of channels, macrovoids and mega-macrovoids. By the first process a cellular structure is formed whilst the second process connects the cells by opening the space between them. The degree of interconnectedness is an additional factor that affects the pure water flux. By changing the cast solution compositions and/or their cast thickness the interconnectedness of the cells can be controlled.
Ključne besede: chemical technology, organic technology, polymer membranes, membrane preparation, wet phase inversion, polymers, polysulphon
Objavljeno v DKUM: 18.08.2017; Ogledov: 1501; Prenosov: 119
.pdf Celotno besedilo (112,47 KB)
Gradivo ima več datotek! Več...

A silver/silver sulphide selective electrode prepared by means of chemical treatments of silver wire
Danilo Dobčnik, Igor Gros, Mitja Kolar, 1998, izvirni znanstveni članek

Opis: The preparation and usability of a sulphide ion selective electrode, prepared by means of chemical pretreatment of silver wire with an ammonium perdisulphate solution, and the sulphidization in an alkaline sulphide solution are described. The electrode is suitable for direct potentiometric measuring of sulphide in alkaline solutions of concentrations down to ▫$1 X 10^{-6} mol/L$▫. The 45 min required for each chemical treatment are enough for the preparation of the described electrode.
Ključne besede: analytical chemistry, ion selective electrode, preparation, silver wire, potentiometric measurements, sulphide ions
Objavljeno v DKUM: 17.08.2017; Ogledov: 1228; Prenosov: 120
.pdf Celotno besedilo (80,69 KB)
Gradivo ima več datotek! Več...

Preparation of WO[sub]3 aerogel catalysts using supercritical CO[sub]2
Zoran Novak, Petra Kotnik, Željko Knez, 2004, izvirni znanstveni članek

Opis: Single tungsten oxide aerogels (WO3), binary oxide aerogels (WO3-Al2O3) and ternary oxide aerogels (WO3-SiO2-Al2O3) were prepared using standard sol-gel route. Tungsten oxide tetraethoxide (WO(OCH2CH3)4) was used as the sol-gel precursor. The excellent properties of the gels obtained by the sol-gel synthesis were preserved upon supercritical drying with CO2. After supercritical drying at 40 °C and 100 bar, all aerogels were calcined to 800 °C. The influence of the synthesis parameters on the catalytic activity of WO3as supported on silica andžor alumina aerogels was investigated through thetransformation of N-(phosphonomethyl)iminodiacetic acid to N-(phosphonomethyl)glycine. Despite including WO3 into single and mixed silicaand alumina aerogels, high specific surface areas (284-653 m2 g-1) were preserved. Higher conversion was obtained for catalysts with higher ratios of WO3 in the mixed silica-alumina aerogels that were calcined at 800 °C.
Ključne besede: chemical processing, aerogels, catalysts, tungsten oxides, preparation of aerogels, characterisation of aerogels, supercritical CO2, supercritical drying, high pressure technology
Objavljeno v DKUM: 01.06.2012; Ogledov: 1971; Prenosov: 44
URL Povezava na celotno besedilo

Preparation and characterization of poly(high internal phase emulsion) methacrylate monoliths and their application as separation media
Peter Krajnc, Nermina Leber, Dejan Štefanec, Sandra Kontrec, Aleš Podgornik, 2005, izvirni znanstveni članek

Opis: Poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) monolithic supports were prepared by radical polymerisation of the continuous phase of water in oil high internal phase emulsions. Morphology of monolithic materialswas studied by scanning electron microscopy and mercury intrusion porosimetry. The ratio of phase volume and the degree of crosslinking influenced the void size and pore size distribution of resulting polymers. Void sizes between 1 and 10 m were observed and average pore sizes around 100nm. Polymers with 60, 75, 80 and 90% pore volume were prepared and even samples with highest pore volume showed good mechanical stability. They were modified to bear weak-anion exchange groups and tested on the separation of standard protein mixture containing myoglobin, conalbumine and trypsin inhibitor. Good separation was obtained in a very short time similar to the separation obtained by commercial methacrylate monoliths. However, higher dispersion was observed. Bovine serum albumin dynamic binding capacity for monolith with 90% porosity was close to 9 mg/ml.
Ključne besede: organic chemistry, methacrylate monoliths, preparation, emulsion polymerization, high porosity, high mechanical stability, polymer chromatographic supports, monolithic methacrylate supports, protein separation
Objavljeno v DKUM: 01.06.2012; Ogledov: 2389; Prenosov: 61
URL Povezava na celotno besedilo

Oil-in-water high internal phase emulsions for porous monolithic polymers
Peter Krajnc, Dejan Štefanec, 2005, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Porous monolithic polymers are objects of many studies recently due to their wide applicability. Especially in separation methods use of monoliths is growing. Usually, porous monoliths are prepared by bulk polymerisation with the use of porogenic solvents. An alternative way of preparation is to polymerise the continuous phase of an emulsion. When the volume fraction of the internal phase exceeds 74%, the emulsion is called a HIPE (high internal phase emulsion), and a polymer derived from it, a PolyHIPE. PolyHIPEs of styrene, vinylbenzyl chloride and acrylate chemistry have been prepared from awater in oil emulsion system, where monomers are dissolved in the organic phase. We describe the reversed procedure, an oil in water high internal phaseemulsion, where monomers are water soluble. Porous polymers based on acrylic acid and crosslinked with methylenebisacrylamide were prepared by using a high internal phase emulsion with toluene as the oil phase. The influence of initiator and surfactant on the morphology was studied.
Ključne besede: organic chemistry, porous monolith polymers, polymer supports, preparation, emulsion polymerization, HIPE
Objavljeno v DKUM: 01.06.2012; Ogledov: 3289; Prenosov: 86
URL Povezava na celotno besedilo

Wet-phase-separation membranes from the polysulfone/N,N-dimethylacetamide/water ternary system: the formation and elements of their structure and properties
Črtomir Stropnik, Vladimir Kaiser, Vojko Musil, Milan Brumen, 2005, izvirni znanstveni članek

Opis: Asymmetric and porous polysulfone (PSf) membranes were prepared by wet phase separation. Binary (PSf)/N,N-dimethylacetamide (DMA) solutions with polymer concentrations of 12.5-30 wt % were cast in thicknesses of 80-700 m and immersed in a coagulation bath of pure water. The morphology of the formed membranesć cross sections consisted of a cellular structure and macrovoidsč the cellular structure density was highest when the cast solution contained about 21 wt % PSf, regardless of the cast thickness. The membranesć pure waterpermeability decreased as the cast thickness increased. The instantaneousonset of the turbidity, regardless of the PSf content and cast thickness, its steep growth, and relatively high end value were the main characteristics of the turbidity phenomena taking place during the formation of the protomembranes. Again, the membrane-forming system with a PSf/DMA solution with about 21 wt % polymer, regardless of the cast thickness, had thehighest turbidity end value. The shrinkage of the cast solutions into the corresponding protomembrane was also examined quantitatively. Inverse experiments showed that the direction of the gravitation field had no influence on the shrinkage of the membrane-forming ternary system or the membranesć morphology and its water permeability.
Ključne besede: polymeric membranes, polysulfone asymmetric porous membranes, wet-phase separation, membrane preparation, morphology
Objavljeno v DKUM: 01.06.2012; Ogledov: 1928; Prenosov: 87
URL Povezava na celotno besedilo

Metallographic sample preparation of orthodontic Ni-Ti wire
Lidija Zorko, Rebeka Rudolf, 2009, izvirni znanstveni članek

Opis: Shape memory alloys (SMA) has been at the forefront of research for the last several decades. In this field especially, Nickel-Titanium (Ni-Ti) alloys have been found to be the most useful of all SMA. The most important applications of SMA Ni-Ti alloys are namely in medicine and dentistry, where they are used as orthodontic wires. In this paper we describe the procedure of preparing metallographic samples of typical orthodontic Ni-Ti wires which are nowadays used in dentistry praxis. We prepared the samples for microstructure observation using a light microscope. Special attention is given to the metallographic preparation, which could result in damages and deformations of the sample surfaces if the procedure is incorrect. Finally, we illustrated the typical metallographic recipe for Ni-Ti SMA alloys for optical observation.
Ključne besede: shape memory alloys, Ni-Ti wire, metallographic preparation, microstructure
Objavljeno v DKUM: 31.05.2012; Ogledov: 2052; Prenosov: 54
URL Povezava na celotno besedilo

Iskanje izvedeno v 13.49 sek.
Na vrh
Logotipi partnerjev Univerza v Mariboru Univerza v Ljubljani Univerza na Primorskem Univerza v Novi Gorici