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11.
Uravnavanje vsebnosti železa v Zn-fosfatni kopeli med procesom Zn-fosfatiranja
Matej Stupan, 2015, undergraduate thesis

Abstract: Namen diplomskega dela je bil uravnavati vsebnost železa med procesom cink-fosfatiranja v cink-fosfatni kopeli s temperaturo 55°C in pH 2. Cink-fosfatna prevleka se uporablja kot porozen medij in na surovcu služi kot podlaga, na katero se nanese milo. Milo deluje kot mazalno sredstvo pri hladnem preoblikovanju na stiskalnici, saj olja zaradi svojih fizikalnih lastnostih niso primerna in bi v najslabšem primeru lahko prišlo do zvara med orodjem in obdelovalcem. Prevleka ima značilno sivo barvo, po kateri se lahko tudi piše. Zaradi prevelike vsebnosti železa prihaja do napak pri nadaljnjih postopkih hladnega preoblikovanja na stiskalnicah. Obdelovanci imajo optimalne lastnosti pri koncentraciji železa okoli 4 g/L. Pri koncentracijah višjih od 7 g/L je potrebno fosfatno kopel izprazniti in nastaviti novo. Pri tem se pojavijo dodatni stroški, saj se celoten proces zaustavi, potreben je nakup novih kemikalij in obdelava odpadnih voda na čistilni napravi. Namen dela je bil uravnati koncentracijo železa na želen nivo. S tem bi dosegli višjo kvaliteto polizdelkov in znižali stroške za nakup kemikalij. Proces proizvodnje bi potekal brez večjih prekinitev, saj je pri previsoki koncentraciji potrebno fosfatno kopel prečrpati v čistilno napravo in nastaviti novo. S predlagano metodo bi se zmanjšal strošek čistilne naprave za obdelovanje težkih kovin, hkrati bi doseli nižjo stopnjo onesnaženosti reke z izpusti.
Keywords: cink-fosfat, železo, površinska zaščita, fosfatiranje
Published: 29.10.2015; Views: 793; Downloads: 102
.pdf Full text (1,96 MB)

12.
INHIBICIJSKA UČINKOVITOST NEIONSKEGA SURFAKTANTA TRITON-X-100 V KLOROVODIKOVI KISLINI
Tamara Zadravec, 2015, undergraduate thesis

Abstract: Namen diplomskega dela je bil s pomočjo gravimetrijske metode določiti inhibicijske lastnosti neionskega surfaktanta TRITON-X-100 v primeru točkaste korozije na nerjavnem jeklu PROKRON 11sp v klorovodikovi kislini. Izbrali smo si raztopino kisline HCl štirih različnih koncentracij: c = 1,0 mol L-1, 0,5 mol L-1, 0,1 mol L-1 ter 0,05 mol L-1. Koncentracije dodanega inhibitorja TRITON-X-100 so bile sledeče; c = 5×10-3, 10-3, 5×10-4, 10-4 ter 5×10-5 mol L-1. Pri raztopini kisline s koncentracijo c = 1,0 mol L-1 ter 0,5 mol L-1 so bile uporabljene koncentracije TRITON-X-100 c = 5×10-3 mol L-1, 5×10-4 mol L-1 in 5×10-5 mol L-1. Pri raztopini kisline s koncentracijo c = 0,1 mol L-1 smo zraven teh koncentracij TRITON-X-100 dodali še koncentracijo c = 10-3 mol L-1, medtem ko smo pri raztopini kisline koncentracije c = 0,05 mol L-1 uporabili še koncentracijo TRITON-X-100 c = 10-4 mol L-1. Podrobneje smo obdelali raztopino klorovodikove kisline HCl s koncentracijo c = 0,05 mol L-1, kateri smo dodali pet različnih koncentracij neionskega surfaktanta TRITON-X-100. Zanimal nas je predvsem pojav prirastka mase, ki se pojavi prav v primeru pri že prej omenjeni koncentraciji klorovodikove kisline. Ugotovili smo, da ta pojav ni naključje, saj se pojavi pri vseh dodanih koncentracijah neionskega surfaktanta TRITON-X-100, kar nakazuje na uspešno inhibicijo zaradi nastale adsorbirane plasti. Proučevali smo korozijsko dogajanje v mirujočem korodirnem mediju v časovnih razmakih dveh, osmih in štiriindvajsetih ur. Uporabili smo gravimetrično metodo ter slikanje površin jekla z uporabo optičnega mikroskopa. Ugotovili smo, da inhibitor TRITON-X-100 že pri nizkih koncentracijah zadovoljivo inhibira korozijske procese v raztopinah klorovodikove kisline.
Keywords: korozija, točkasta kroozija, surfaktanti, učinkovitost inhibitorjev, gravimetrična metoda
Published: 29.10.2015; Views: 1000; Downloads: 64
.pdf Full text (1,59 MB)

13.
Impedance measurements on the passive layers of stainless different heat treated steels
Mojca Slemnik, Valter Doleček, Miran Gaberšček, 2002, short scientific article

Abstract: The behavior of differently heat-treated X20Cr13 steels in 0.1 M H2SO4, was studied using the electrochemical impedance spectroscopy. Impedance spectra were recorded at constant passsive potentials of 0.2, 0.4 and 0.6 V vs. SCE, respectively. At low passive potential, 0.2 V vs. SCE, impedance spectra typical for an active - passive transition were observed. The assumption has been made, that they are the result of the adsorption process, caused by boundwater, which blocks the passive layer of steel and leads to corrosion rate reduction. The process is the most significant at the oil and the air-quenched, but less at the tempered steel. When more noble potentials are approached the impedance spectra become typical for passive metals and the value of resistance and capacitance differ from each other with respect to the heat treatment.
Keywords: korozija, nerjavna jekla, impedanca
Published: 10.07.2015; Views: 982; Downloads: 23
URL Link to full text

14.
Electrochemical impedance spectroscopy as a tool in the plate making process optimization
Tomislav Cigula, Regina Fuchs-Godec, Miroslav Gojo, Mojca Slemnik, 2012, original scientific article

Abstract: The structure of the porous aluminium-oxide layer, which builds non-image areas, has the most significant influence on the quality of final graphical product. This paper presents the results of the application of EIS in the characterisation and detection of changes on the aluminium-oxide layer caused by chemical processing in highly alkaline solution. The Al2O3 layer was characterised using SEM, fractal dimension and surface free energy calculationand EIS analysis. The results of the investigation showed that chemical processing has a significant influence on the structure of aluminiumoxide which could lead to a decrease in the quality of the printing plate. EIS enables the detection of changes on the aluminium- oxide layer. Thetwo equivalent circuits are proposed. Based on modelling with the obtained EIS spectra, precise evaluation of developing time in which complete removal of the photoactive layer is achieved. This makes EIS a powerful tool in optimizing chemical processing of lithographic printing plates.
Keywords: printing plate, chemical processing, SEM, surface free energy, EIS
Published: 10.07.2015; Views: 756; Downloads: 66
.pdf Full text (266,51 KB)
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15.
Poskusi v fizikalni kemiji : zbrano gradivo, zbirka vaj
Mojca Slemnik, 2014, other educational material

Abstract:
Keywords: fizikalna kemija, laboratorijski poskusi, učbeniki
Published: 01.07.2014; Views: 1271; Downloads: 117
.pdf Full text (1,14 MB)

16.
Pojavi na površinah : zbrano gradivo, zbirka vaj
Mojca Slemnik, Regina Fuchs-Godec, 2014, other educational material

Abstract:
Keywords: površinski pojavi, površinska kemija, učbeniki
Published: 24.06.2014; Views: 820; Downloads: 54
.pdf Full text (572,21 KB)

17.
SISTEM ZAGOTAVLJANJA KAKOVOSTI V CENTRU ZA TRANSFUZIJSKO DEJAVNOST NOVO MESTO
Silva Kotar, 2012, undergraduate thesis

Abstract: V diplomski nalogi sem predstavila sistem zagotavljanja kakovosti v Centru za transfuzijsko dejavnost Novo mesto (CTD NM). CTD NM je ena izmed dislociranih enot Zavoda Republike Slovenije za transfuzijsko medicino (ZTM). ZTM vodi politiko celovitega sistema kakovosti. V gospodarstvu poznajo sisteme kakovosti že desetletja, saj so podjetja s pridobljenimi certifikati kakovosti lažje prodirala na trg. Na področju zdravstva, pa tako v svetu kot tudi pri nas, uvajajo sisteme kakovosti šele v zadnjih desetletjih. Glavni cilj sistemov kakovosti v zdravstvu je zagotavljanje večje varnosti za pacienta. Na CTD NM imamo tak sistem zagotavljanja kakovosti, da spremljamo vse ključne parametre, ki bi lahko vplivali na kakovost krvnih komponent in laboratorijskih storitev. Pri tem smo morali upoštevati Zakon o preskrbi s krvjo in pravilnike, ki se nanašajo na transfuzijsko dejavnost. V diplomski nalogi sem opisala zakonske normative in način vpeljave normativov v sistem zagotavljanja kakovosti na CTD NM. Na CTD NM nadzorujemo vse postopke, od sprejema krvodajalca do izdaje krvi, in vse postopke pri laboratorijskih storitvah. Le z doslednim izvajanjem in nadgrajevanjem sistema zagotavljanja kakovosti lahko pacientom zagotovimo kakovostne laboratorijske storitve in varne komponente krvi.
Keywords: sistem kakovosti, transfuzijska dejavnost, krvne komponente, krvodajalec
Published: 21.06.2012; Views: 1747; Downloads: 184
.pdf Full text (1,68 MB)

18.
Substitution of the constant phase element by Warburg impedance for protective coatings
Saša Skale, Valter Doleček, Mojca Slemnik, 2007, original scientific article

Abstract: This paper proposes an alternative model for fitting electrochemical impedance spectra of protective coatings. It describes broadening of the semicircle in the complex plane, in the absence of corrosion reactions. In addition the infinite Warburg impedance circuit element is represented, which bridges existing parallel elements of the plate capacitor and resistor of a classical equivalent electrical circuit. The Warburg impedance element is the result of the Fick's second law on partial differential equation solution. The proposed model and, for comparison the model with the CPE element, are used on our epoxy protective system to describe EIS measurements. The proposed model shows a better quality of fitting for our EIS data in comparison to the model with CPE.
Keywords: metal-coatings, electrochemical impedance spectroscopy, Nyquist charts, constant phase element, Warburg impedance
Published: 01.06.2012; Views: 1683; Downloads: 93
URL Link to full text

19.
Effect of testing temperature on corrosion behaviour of different heat treated stainless steels in the active-passive region
Mojca Slemnik, 2008, original scientific article

Abstract: Purpose - This paper aims to focus on the effects of temperature of the immersion media on the corrosion behaviour of differently heat-treated X20Cr13 stainless steel. Design/methodology/approach - Specimens, quenched on air, quenched in oil and quenched in oil and then tempered, were tested during exposure in 0.1?M H2SO4 at 30, 40 and 50°C. The results were interpreted on the base of potentiodynamic and impedance measurements. Findings - From the impedance spectra a reaction mechanism can be determined: after samples had reached and passed the active peak, expressed as the highestpeak on the potentiodynamic curve, corrosion products at interfaces, which were adsorbed at metal surface, led to an increase in the charge transfer resistance. Elevated temperature of immersion media has had appreciable influence on the corrosion rate and adsorption of products, but atthis temperature level did not affect the principle of corrosion reactions. Activation energies were calculated to exhibit temperature dependence of current density, which was the highest for the oil- and the lowest for the air-quenched sample. Originality/value - The paper provides further research on stainless steel, the corrosion behaviour of which can be controlled already by heat treatment.
Keywords: corrosion, stainless steel, heat treatment, temperature
Published: 01.06.2012; Views: 1151; Downloads: 89
URL Link to full text

20.
Experiments in physical chemistry : zbrano gradivo za tuje študente
Mojca Slemnik, 2011, other educational material

Published: 01.06.2012; Views: 899; Downloads: 35
URL Link to full text

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