No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

The aim of this study was to compare the barrier properties of organic coatings with the same polymer matrix but different types of iron oxide particles, commercial and recycled. The work was carried out for the company SSAB with the aim of investigating whether the pigment Merox ferric oxide, which is produced in-house at the company during the pickling process, can be used and replace commercial iron oxide pigment. Evaluation of the barrier properties was done using electrochemical impedance spectroscopy where the capacitance of the coatings is calculated and reflects the water absorption of the coating over a period of exposure to the electrolyte. By comparing the capacitance of the different coatings, an estimation of the water transport through the different coatings was made. Complementary methods used were digital optical microscopy and scanning electron microscopy.  In this project, 6 lab samples were evaluated. In common, the samples consisted of the same metal substrate, hot-dip galvanized steel, and the binder in the coatings was polyester-melamine. Sample 1 consisted of the binder only, sample 2 contained the commercial iron oxide pigment, samples 3 and 4 consisted of Merox pigments but different levels of chlorine in the pigment. The thickness of the coatings of the 4 samples was 6 m. Sample 5 had a thicker coating of 20 m and contained Merox pigment. The last sample evaluated was a reference sample with anti-corrosive pigment with a thickness of 20 m. Furthermore, exposure tests were carried out with sample 5 to test how different electrolyte solutions affected the samples. The electrolytes tested were 1 M Na2SO4 (for reference), 1 M NaNO3 and 0.1 M NaCl.  The impedance measurements were performed in 3 parallel measurements on the samples with thinner coating (6 m) and an average of the capacitance was used to analyze how the capacitance changes over time. The results showed that sample 1 had much better barrier properties than the samples containing iron oxide pigments, although the exposure time to electrolyte was longer for this sample, the capacitance was lower. Both samples 2 and 4 increased rapidly in capacitance over a short period of time. Sample 3 had a rapid increase at the beginning which later decreased, the sample showed better barrier properties compared to samples 2 and 4. Cross-sectional studies carried out by scanning electron microscopy detected corrosion formation between the zinc and the coating on all samples with thinner coatings. Only one impedance measurement was made on samples 5 and 6, hence multiple measurements need to be performed to calculate the capacitance over time and provide complete and reliable results for these samples.  The results of the exposure tests indicated that the electrolyte used for the electrochemical impedance measurements, 1 M Na2SO4 is more corrosive than the other electrolytes tested, 1 M NaNO3 and 0.1 M NaCl. / Syftet med denna studie var att jämföra barriärsegenskaper hos organiska beläggningar med samma polymer matris men olika typer av järnoxidpartiklar, kommersiella och återvunna. Arbetet utfördes åt företaget SSAB med målet att undersöka om pigmentet Merox ferric oxide, vilket produceras internt på företaget under betningsprocessen, kan användas och ersätta kommersiellt järnoxidpigment. Utvärdering av barriärsegenskaperna gjordes med elektrokemisk impedansspektroskopi där beläggningarnas kapacitans beräknas och avspeglar vattenabsorption av beläggningen över en tidsperiod av exponering till elektrolyt. Genom att jämföra kapacitansen för de olika beläggningarna, har en estimering av vattentransporten genom de olika beläggningarna gjorts. Kompletterande metoder som användes var digitalt optiskt mikroskop och svepelektronmikroskopi.  I detta projekt utvärderades 6 labb-prover. Gemensamt bestod proverna av samma metallsubstrat, varmförzinkat stål och bindaren i beläggningarna var polyester-melamine. Prov 1 bestod endast av bindaren, prov 2 innehöll kommersiellt järnoxidpigmentet. Prov 3 och 4 bestod av Merox pigment men olika halter av klor i pigmentet. Tjockleken på beläggningarna hos de 4 proverna var 6 m. Prov 5 hade en tjockare beläggning på 20 m och innehöll Merox pigment. Det sista provet som utvärderades var ett referensprov med anti-korrosivt pigment med en tjocklek på 20 m. Vidare gjordes exponeringstester med prov 5 för att testa hur olika elektrolytlösningar påverkade proverna. Elektrolyterna som testades var 1 M Na2SO4 (som referens), 1 M NaNO3 och 0,1 M NaCl.  Impendansmätningarna utfördes i 3 parallella mätningar på proverna med tunnare beläggning (6 m) och ett medelvärde av kapacitansen användes för att analysera hur kapacitansen förändras över tiden. Resultatet visade att prov 1 hade mycket bättre barriärsegenskaper än proverna som innehöll järnoxid pigment, även fast exponeringstiden gentemot elektrolyt var längre för detta prov så var kapacitansen lägre. Både prov 2 och 4 ökade snabbt i kapacitans under en kort tidsperiod. Prov 3 hade en snabb ökning i början som senare avtog, provet visade bättre barriärsegenskaper jämfört med prov 2 och 4. Tvärsnittsstudier som genomfördes med svepelektronmikroskopi detekterade korrosionsbildning mellan zink och beläggningen på alla prover med tunnare beläggning. Endast en impedansmätning på prov 5 och 6 utfördes, därav behövs flera mätningar genomföras för att kunna beräkna kapacitansen över tid och ge fullständiga och pålitliga resultat för dessa prover.  Resultaten från exponeringstesterna visade på att elektrolyten som använts för elektrokemiska impedansmätningarna, 1 M Na2SO4 är mer korrosiv än de andra elektrolyterna som testades, 1 M NaNO3 och 0,1 M NaCl.

<p>This thesis presents an investigation into the structure and composition of the surface film formed on Mg in aqueous solutions and describes the influence of film stability on corrosion resistance. The composition and structure of the surface film formed on pure Mg in pure H₂O exposed at E_corr for 48 h was investigated using plan-view SEM-EDS imaging and STEM–EDS analysis of a FIB cross-section. The film formed was duplex in nature, consisting of a thinner, more-porous, nano-crystalline MgO-rich inner layer (50-100 nm), and a thicker, less-porous, Mg(OH)₂-rich outer platelet layer (700 nm). The results were consistent with the theory that a chemical breakdown (hydration) of the bulk inner MgO layer (native oxide) is a necessary precursor step to the corrosion process resulting in a significant thickening of the partially protective outer Mg(OH)₂ layer.</p> <p>The surface film formed on pure Mg exposed in 0.01 M NaCl for 24 h at E_corr was found to be a diffuse bilayer structure similar to pure H₂O, including a thin and porous nano-crystalline MgO-rich inner layer (50-100 nm), and a thicker, more porous Mg(OH)₂-rich outer layer (300-600 nm). The un-pitted film region formed in 0.01 M NaCl solution at +0.1 V above E_b for 0.5 h after 24 h aging at E_corr exhibited a similar duplex structure. However, the thickness of both Mg(OH)₂-rich (~450 nm) and MgO-rich layers (~30-60 nm) appeared to be decreased. Furthermore, the pitted region film formed on an anodically polarized Mg sample exhibited thinner MgO-rich layer (~20-30 nm), decorated with macro-pores (~50 nm), and Mg(OH)₂ rich middle layer (~200-300 nm) buried under a thick, more porous needle-like Mg(OH)₂-rich top layer (~0.2-1 µm). EDS analysis confirmed the presence of Cl within the films formed in 0.01 M NaCl, and Fe containing particles within the pitted region anodic film. These results were consistent with an accelerated hydration of MgO to Mg(OH)₂ at lower pH and in presence of Cl^-, formation of more soluble Mg-hydroxy-chlorides, enhanced Mg dissolution due to Cl^- ingress via increased film porosity, and influence of more noble impurities on the pit initiation and growth.</p> <p>The ~50-150 nm film formed spontaneously on Mg exposed to 1 M NaOH was found to consist mainly of a crystalline MgO layer that has been hydrated to Mg(OH)₂ to a variable degree. Although the film exhibited excellent corrosion resistance, it was not stable. The film tended to experience an irregular breakdown/repair process, which was characterized by large irregular potential drops (about 1 V) under E_corr conditions. The breakdown/repair process is believed to involve the hydration-induced stress-rupture of the MgO film at discrete sites and the subsequent formation of a Mg(OH)₂ self-healing corrosion product nodule (~ 500 nm).</p> <p>To understand the corrosion mechanisms and propose surface film evolution models, EIS behavior of Mg in all environments was investigated. The EIS spectra were compared with the proposed Nyquist behavior based on the film structure results. It was confirmed that the diffuse bilayer films formed in pure H₂O and 0.01 M NaCl possessed porosity, in which the electrolyte ingressed, forming the double layer and facilitating Mg faradic dissolution reaction across the Mg/film interface. Decreased porosity and R_ct along with the absence of a C_film/R_por loop, were respectively consistent with lower corrosion resistance of Mg in 0.01 M NaCl and a severely damaged pitted region film. Furthermore, the film compactness and increased R_ct in 1 M NaOH were consistent with a more stable film with excellent corrosion resistance in alkaline environments. In this film, liberated Mg²⁺ ions at the Mg/film interface have to diffuse through the film to facilitate the Mg(OH)₂ precipitation, thus a thicker Mg(OH)₂ film forms.</p> / Doctor of Philosophy (PhD)

Polyimides are frequently used as insulating layers in the microelectronics industry. These polymers are tough, have high thermal stability, and have favorable dielectric properties; consequently, polyimides are excellent materials for insulating layers in microelectronic devices. In this research, self-assembled monolayers are investigated for use as an adhesion promoter for metal substrates, and for corrosion protectors of the metal surface. Gold substrates modified by adsorption of 3- and 4-aminothiophenol monolayers, 3- and (4-mercaptophenyl) phthalimide (MPP) monolayers, and by reaction of the 3- and 4-aminothiophenol monolayers with the phthalic anhydride were studied using reflection absorption infrared spectroscopy, contact angle measurement, ellipsometry, and electrochemical measurements. Reactions on the monolayers are used to model the attachment of an insulating polyimide to the substrate. The covalent attachment of the anhydride is confirmed, and the efficiency of the reaction of the aminothiolphenol monolayers is investigated. The reactivity of the aminothiolphenol monolayers is found to depend on the position of the amino-group around the phenyl ring. Impedance spectroscopy is used to investigate the ionic insulating properties of these systems. The 4-mercaptophthalimide monolayer is found to have the highest monolayer resistance to ion transport. This result suggests that it forms the most densely packed monolayer. The monolayer resistance of the surfaces prepared by adsorption of the aminothiolphenol isomers followed by reaction with phthalic anhydride is much lower than the corresponding deposited mercaptophthalimide monolayers. These results suggest that the reaction efficiency is low. Impedance spectroscopy and polarization measurements suggests a higher protection efficiency for 3-mercaptophenylphthalimide. These results will be discussed in the context of the ability of the isomeric mercaptophthalimide monolayers to serve as protectors against substrate corrosion. / Ph. D.

Yes / Rapid point of care tests for bacterial infection diagnosis are of great importance to reduce the misuse of antibiotics and burden of antimicrobial resistance. Here, we have successfully combined a new class of non-biological binder molecules with electrochemical impedance spectroscopy (EIS)-based sensor detection for direct, label-free detection of Gram-positive bacteria making use of the specific coil-to-globule conformation change of the vancomycin-modified highly branched polymers immobilized on the surface of gold screen-printed electrodes upon binding to Gram-positive bacteria. Staphylococcus carnosus was detected after just 20 min incubation of the sample solution with the polymer-functionalized electrodes. The polymer conformation change was quantified with two simple 1 min EIS tests before and after incubation with the sample. Tests revealed a concentration dependent signal change within an OD600 range of Staphylococcus carnosus from 0.002 to 0.1 and a clear discrimination between Gram-positive Staphylococcus carnosus and Gram-negative Escherichia coli bacteria. This exhibits a clear advancement in terms of simplified test complexity compared to existing bacteria detection tests. In addition, the polymer-functionalized electrodes showed good storage and operational stability.