Print quality demands for coated papers are steadily growing, and achieving coating uniformity is crucial for high image sharpness, colour fidelity, and print uniformity. Coating uniformity may be divided into two scales: coating thickness uniformity and coating microstructure uniformity, the latter of which includes pigment, pore and binder distributions within the coating layer. This thesis concerns the investigation of both types of coating uniformity by using an approach of quantitative microscopy.First, coating thickness uniformity was analysed by using scanning electron microscope (SEM) images of paper cross sections, and the relationships between local coating thickness variations and the variations of underlying base sheet structures were determined. Special attention was given to the effect of length scales on the coating thickness vs. base sheet structure relationships.The experimental results showed that coating thickness had a strong correlation with surface height (profile) of base sheet at a small length scale. However, at a large length scale, it was mass density of base sheet (formation) that had the strongest correlation with coating thickness. This result explains well the discrepancies found in the literature for the relationship between coating thickness variation and base sheet structure variations. The total variance of coating thickness, however, was dominated by the surface height variation in the small scale, which explained around 50% of the variation. Autocorrelation analyses were further performed for the same data set. The autocorrelation functions showed a close resemblance of the one for a random shot process with a correlation length in the order of fibre width. All these results suggest that coating thickness variations are the result of random deposition of particles with the correlation length determined by the base sheet surface textures, such as fibre width.In order to obtain fundamental understandings of the random deposition processes on a rough surface, such as in paper, a generic particle deposition model was developed, and systematic analyses were performed for the effects of particle size, coat weight (average number of particles), levelling, and system size on coating thickness variation. The results showed that coating thickness variation3grows with coat weight, but beyond a certain coat weight, it reaches a plateau value. A scaling analysis yielded a universal relationship between coating thickness variation and the above mentioned variables. The correlation length of coating thickness was found to be determined by average coat weight and the state of underlying surfaces. For a rough surface at relatively low coat weight, the correlation length was typically in the range of fibre width, as was also observed experimentally.Non-uniformities within the coating layer, such as porosity variations and binder distributions, are investigated by using a newly developed method: field emission scanning electron microscopy (FESEM) in combination with argon ion beam milling technique. The combination of these two techniques produced extremely high quality images with very few artefacts, which are particularly suited for quantitative analyses of coating structures. A new evaluation method was also developed by using marker-controlled watershed segmentation (MCWS) of the secondary electron images (SEI).The high resolution imaging revealed that binder enrichment, a long disputed subject in the area, is present in a thin layer of a 500 nm thickness both at the coating surface and at the base sheet/coating interface. It was also found that the binders almost exclusively fill up the small pores, whereas the larger pores are mainly empty or depleted of binder.

<p>The spectroscopic, SEM and Raman measurements on carbon nanotubes under the exact conditions of which OES analysis were made showed that at<br /> a pressure of 400 Torr and a flow rate of 200 sccm, the quality and quantity of single-walled carbon nanotubes was the highest.</p>

<p>The main hypothesis in this study is the development of a nanocomposite mediated amperometric biosensor for detection of hydrogen peroxide. The aim is to combine the electrochemical properties of both polyaniline and ferrocenium hexafluorophosphate into highly conductive nano composites capable of exhibiting electrochemistry in non acidic media / shuttling electrons between HRP and GCE for biosensor applications.</p>

A study was done to determine the temperature and load interaction effects on the fatigue crack growth rate of polycrystalline superalloy IN100. Temperature interaction testing was performed by cycling between 316°C and 649°C in blocks of 1, 10 and 100 cycles. Load interaction testing in the form of single overloads was performed at 316°C and 649°C. After compiling a database of constant temperature, constant amplitude FCGR data for IN100, fatigue crack growth predictions assuming no load or temperature interactions were made. Experimental fatigue crack propagation data was then compared and contrasted with these predictions. Through the aid of scanning electron microscopy the fracture mechanisms observed during interaction testing were compared with the mechanisms present during constant temperature, constant amplitude testing. One block alternating temperature interaction testing grew significantly faster than the non-interaction prediction, while ten block alternating temperature interaction testing also grew faster but not to the same extent. One hundred block alternating testing grew slower than non-interaction predictions. It was found that as the number of alternating temperature cycles increased, changes in the gamma prime morphology (and hence deformation mode) caused changes in the environmental interactions thus demonstrating the sensitivity of the environmental interaction on the details of the deformation mode. SEM fractography was used to show that at low alternating cycles, 316°C crack growth was accelerated due to crack tip embrittlement caused by 649°C cycling. At higher alternating cycles the 316°C cycling quickly grew through the embrittled crack tip but then grew slower than expected due to the possible formation of Kear-Wilsdorf locks at 649°C. Overload interaction testing led to full crack retardation at 2.0x overloads for both 316°C and 649°C testing. 1.6x overloading at both temperatures led to retarded crack growth whereas 1.3x overloads at 649°C created accelerated crack growth and at 316°C the crack growth was retarded.

Myringotomy plays an important role in otological therapy. The procedure requires an efficient anesthesia, which can be obtained without general anesthesia. However, the use of local anesthetics on the tympanic membrane (TM) has been abandoned in many places, as general anesthesia has been readily available. In the present study the effects of some commonly used topical anesthetics on the TM structure and inner ear were tested in an animal model (rat and guinea pig).Four different anesthetic compounds—Xylocaine®, Bonain's liquid, phenol and Emla®—were applied to the TMs of the animals, which were sacrificed 10 minutes to 5 months after application. Morphological effects regarding time after treatment and number of applications were elucidated. At sacrifice the tissue was fixed and the TMs analysed by light microscopy (LM) and transmission electron microscopy (TEM). In nine animals phenol, Xylocaine® Spray or Emla® was applied to the round window niche and ABR recordings were made at 24 h to 6 months after exposure. After the final ABR evaluation the animals were sacrificed and the cochleae prepared for LM and scanning electron microscopy (SEM).On the TM phenol and Bonain's liquid caused instant destruction of the keratinizing stratified squamous epithelium followed by long-lasting hyperplasia of this epithelium and the underlying connective tissue. A pronounced hyperplasia of these two layers was also noted for the Xylocaine® Spray group, but without immediate destruction of the keratinizing epithelium. The extent of structural changes differed in relation to the extent of spreading of the agent. Emla® showed little, if any, sign of epithelial reaction and had no effect on the connective tissue. Regarding the inner ear Emla®, Xylocaine® Spray and phenol induced significantly impaired ABR thresholds mainly affecting the higher frequencies. However, the impaired ABR thresholds were reversible and at the end of the experiment there was no significant impairment compared to the control data. All agents, except Xylocaine®, damaged the hair cells in the basal part of the cochlea as shown by cytocochleogram and SEM analysis.Instant destruction of the epidermis seems to be necessary for an instant anesthetic effect. All agents caused profound connective tissue reactions. The manner of application, depending on the physical properties of the agent, determined the extent of the structural changes. The changes of the connective tissue were concentrated to the submucosal layer, which seems to be the area for reconstruction of the damaged TM. All agents caused functional inner ear changes. With the exception of Xylocaine® they also caused morphological alterations of the cochlea. The functional changes were partly reversible. Topical anesthetics applied to the TM should be used with caution and when used in an appropriate manner they can be considered safe, especially in an inflamed middle ear, with a thickened round window membrane, which should prevent the agents from reaching the inner ear structures. / digitalisering@umu

Imitation of archeological artifacts or replacing the authentic ones with fake replicates is a universal problem / it is particularly important in Turkey for historical metal objects. Traditionally used visual inspection methods alone are not sufficient for the solution of contemporary problems. In this study, chemical characterization has been used to determine the differences between the authentic and fake objects. The non-destructive analyses were carried out by Portable X-ray Fluorescence Spectrometry (P-XRF). Silver Roman Coins (27 B.C. to 244 A.D.) were the objects handled in this research. In particular the concentrations of Zr, Pt, Pb and Bi were used for differentiation / it has been observed that the concentrations have different trends in the authentic and fake silver coins. In authentic coins the average Pb concentration was found to be 0.77%, while this value was 0.055% for the fake ones. Bi could be determined in 86% of the authentic coins while it could not be detected in any fake coin. It has been generally observed that the silver and copper concentrations could not be utilized in authenticity tests. Another approach was the use of Line Scanning Electron Microscopy-Energy Dispersive X-Ray Fluorescence Spectrometry (LSEM-EDX). Using LSEM-EDX technique, it was observed that the concentration changes near the interface between the matrix and the copper-rich locations exhibits difference behaviors for the authentic and fake objects. This difference is originated by the fact that a newly formed copper amalgam contains copper-rich phases while with extended time concentration changes at interfaces become more gradual or not detectable. Pearson correlation was used in order to elucidate the relations between the element concentrations determined by P-XRF. In order to see whether the authentic and silver fake coins can form separate groups, dendograms have been constructed utilizing SPSS 16.0 software and Euclidian Square Distance method. It has been observed that the authentic and fake coins can be successfully grouped when the proper statistical choices are used. It has been observed that these groups have significant differences using t-test. The selected and used technology is proposed for use by museums and entities keeping archaeological collections in order to prevent forgeries.

Cycling of the relative humidity (RH) levels in the reactant streams of polymer electrolyte membrane (PEM) fuel cells has been reported to decay fuel cell performance. This study focuses on the accelerated durability testing to examine different modes of membrane failure via RH cycling. A single PEM fuel cell with an active area of 42.25 cm2 was tested. A Greenlight G50 test station was used to establish baseline cell (Run 1) performance with 840 hours of degradation under high-humidity idle conditions at a constant current density of 10 mA cm-2. Under the same conditions, two other experiments were conducted by varying the RH. For the H2-air RH cycling test (Run 2), anode and cathode inlet gases were provided as dry and humidified gases. Another RH cycling experiment was the H2 RH cycling test (Run 3): the anode inlet gas was cycled whereas keeping the other side constantly at full humidification. These two RH cycling experiments were alternated in dry and 100% humidified conditions every 10 and 40 minutes, respectively. In the experiments, the fuel cells contained a GoreTM 57 catalyst coated membrane (CCM) and 35 BC SGL gas diffusion layers (GDLs). The fuel cell test station had been performed under idle conditions at a constant current density of 10 mA cm-2. Under the idle conditions, operating at very low current density, a low chemical degradation rate and minimal electrical load stress were anticipated. However, the membrane was expected to degrade due to additional stress from the membrane swelling/contraction cycle controlled by the RH. In this work the performance of the 100% RH humidified cell (Run 1) was compared with that of RH cycling cells (Run 2 and Run 3). Chemical and mechanical degradation of the membrane were investigated using in-situ and ex-situ diagnostic methods. The results of each measurement during and after fuel cell operation are consistent. They clearly show that changing in RH lead to an overall PEM fuel cell degradation due to the increase in membrane degradation rate from membrane resistance, fluoride ion release concentration, hydrogen crossover current, membrane thinning, and hot-spot/pin-hole formation.

Land disposal of solid waste is a vital component of any solid waste management system. Design, operation and closure of municipal solid waste (MSW) landfills are required by regulations to control leachate and gases generated during the life, closure,and post-closure of the facility. Clogging of leachate drainage and removal systems in landfills is a common phenomenon and has been acknowledged in several landfills throughout the United States and abroad. This project was conducted in two phases. Phase I was completed in February of 2005 and Phase II was completed in August of 2006. Leachate characteristics data obtained in Phase I was processed and analyzed, along with supplementary data obtained in Phase II on liquid and solid phase testing. Leachate samples from the landfill and lysimeters indicated the presence of iron and sulfate-reducing bacteria. These bacteria are known to facilitate biologically induced precipitate formation.The mechanism by which biologically ind uced precipitate may form begins with oxidizing acetate by iron and sulfate-reducing bacteria, reducing sulfate to sulfide and ferric iron to ferrous, and then forming calcium carbonate, iron sulfate, and possibly dolomite and other minerals.The results show that the clogging mechanism is driven by two major processes: transformation of volatile acids to substrates by iron and sulfate-reducing bacteria causing local pH and total carbonate to increase, which accelerate calcium carbonate precipitation, and thermodynamically favored reactions in supersaturated conditions based on saturation indices of calcium, sulfide, iron, and other species with respect to minerals. For each 1 mg of consumed volatile acids there were 1.7 mg of calcium, 0.28 mg of sulfate, and 0.03 mg of iron removed. Field and lysimeter precipitate samples were analyzed (using X-Ray Diffraction, Scanning Electron microscopy, and Electron Dispersive Spectroscopy) and correlated with geochemical modeling of leachate const ituents. Precipitate analyses showed the presence of calcium carbonate, brushite (calcium phosphate),and dolomite, where as geochemical modeling showed that calcium carbonate, hydroxyapatite (complex of calcium phosphate), dolomite, pyrite, and siderite may be formed from field and lysimeter leachate constituents. The results also showed that submerged and stagnant conditions in the leachate collction systems accelerate the precipitation process.

Το οξείδιο του ψευδαργύρου (ZnO) ανήκει στην κατηγορία των διάφανων αγώγιμων οξειδίων και θεωρείται ως το ανόργανο υλικό που επιδεικνύει τη μεγαλύτερη ποικιλία χαμηλοδιάστατων νανοδομών. Νανοδομές διαφόρων μορφολογιών του ZnO αναπτύσσονται με πλήθος μεθόδων – με κυριότερες την αέρια μεταφορά σε υψηλή θερμοκρασία (VLS) και τη χημεία διαλυμάτων – και παρουσιάζουν μεγάλο εύρος πιθανών εφαρμογών σε τομείς όπως η οπτική, η οπτικοηλεκτρονική, οι αισθητήρες, η παραγωγή ενέργειας, οι βιοϊατρικές επιστήμες, κ.α. Παρά τη συστηματική έρευνα σχετικά με την ανάπτυξη των νανοδομών αυτών για πάνω από μια δεκαετία, η καθιέρωση μιας πειραματικής μεθοδολογίας ικανής να παρέχει με επαναλήψιμο τρόπο συγκεκριμένες μορφολογίες νανοδομών του ZnO είναι ακόμα ένα ανοικτό ερώτημα. Αυτό αποτελεί και μια από τις τρέχουσες ερευνητικές προκλήσεις αφού οι παραγόμενες μορφολογίες χαρακτηρίζονται από διαφορετικές φυσικές ιδιότητες ενώ είναι αρκετά ευαίσθητες σε μικρές μεταβολές των πειραματικών συνθηκών. Στόχος της παρούσας εργασίας είναι η συστηματική μελέτη του ρόλου διαφόρων παραμέτρων της σύνθεσης στα μορφολογικά χαρακτηριστικά και τις οπτικές ιδιότητες των νανοδομών του ZnO. Η ανάπτυξη των νανοδομών πραγματοποιήθηκε τόσο με αέρια μεταφορά σε υψηλή θερμοκρασία (VLS) όσο και με τη μέθοδο της κρυστάλλωσης σε υδατικά διαλύματα (CBD). Σκοπός είναι να κατανοηθεί πως συγκεκριμένες παράμετροι επηρεάζουν τη μορφολογία των νανοδομών, το μέγεθος, τις κατανομές των διαμέτρων των μονοδιάστατων νανονημάτων και τον προσανατολισμό αυτών στο υπόστρωμα. Στην πρώτη περίπτωση δόθηκε έμφαση στο ρόλο του πάχους του υμενίου του καταλύτη (Au), αλλά και στον τρόπο ανόπτησης αυτού ώστε να δημιουργηθεί η κατάλληλη μορφολογία του καταλύτη η οποία μέσω της ανάπτυξης με τη μέθοδο VLS επηρεάζει κατ’ επέκταση και τη μορφολογία των νανοδομών του ZnO. Έτσι, επιχρυσωμένα υποστρώματα πυριτίου (Si) με πάχος καταλύτη (h) από 2 nm έως 15 nm χρησιμοποιήθηκαν μετά από ανόπτησή τους σε διάφορες θερμοκρασίες και για διαφορετικούς χρόνους για την ανάπτυξη νανονημάτων ZnO. Διαπιστώθηκε ότι για πολύ λεπτά υμένια Au (h ≤ 3 nm) δημιουργούνται σφαιρικά νανοσωματίδια χρυσού και ο χρόνος ανόπτησης δεν επηρεάζει τη μορφολογία και την κατανομή μεγεθών. Για παχύτερα υμένια (h ≥ 5 nm), ανόπτηση για σύντομο χρόνο δεν επαρκεί για την ανάπτυξη νανοσωματιδίων αντίστοιχα με αυτά των λεπτών υμενίων. Στην περίπτωση αυτή, η αύξηση του χρόνου ανόπτησης ή/και αύξηση της θερμοκρασίας ανόπτησης είναι επιβεβλημένη για την ελάττωση του μέσου μεγέθους. Εν γένει, ανόπτηση σε χαμηλότερη θερμοκρασία (400 °C) για μεγάλο χρονικό διάστημα (30 λεπτά) μετατρέπει τα υμένια του Au σε νανοσωματίδια με ευρείες κατανομές μεγεθών και υψηλές μέσες τιμές. Η ανάπτυξη νανονημάτων ZnO εξαρτάται από το μέσο μέγεθος των νανοσωματιδίων του Au. Η ανάπτυξη παρεμποδίζεται στα μεγάλα μεγέθη νανοσωματιδίων Au αφού ο υπερκορεσμός τους με Zn και O είναι αργός. Ως εκ τούτου, για τα υμένια Au με πάχος μεγαλύτερο από ~10 nm η ανάπτυξη νανονημάτων του ZnO είναι εξαιρετικά περιορισμένη. Στη δεύτερη περίπτωση, εξετάστηκε διεξοδικά ένα πλήθος παραμέτρων όπως η συγκέντρωση των αντιδρώντων στο διάλυμα, η παρουσία οργανικών ενώσεων για τον έλεγχο της διαμέτρου, οι ιδιότητες του πρόδρομου υμενίου κρυστάλλωσης στο υπόστρωμα, ο χρόνος κρυστάλλωσης, κ.α. Γυάλινα αγώγιμα υποστρώματα (FTO) στα οποία είχε εναποτεθεί πρόδρομο υμένιο πυρηνοποίησης, χρησιμοποιήθηκαν σε αυτή την περίπτωση για την ανάπτυξη νανονημάτων. Καλά προσανατολισμένες δομές κάθετες στο υπόστρωμα με διάμετρο ~30 nm και μήκος μέχρι ~7 μm δημιουργήθηκαν με χρήση 0.04 Μ ZnAc, 0.02 M HMTA, 0.16 M PEI και 0.04 M NH4OH σε υδατικό διάλυμα στους 95 οC. H χρονική διάρκεια των πειραμάτων κυμάνθηκε στο διάστημα 1 – 24 h. Η τιμή του pH του διαλύματος ήταν περίπου 7. Ο προσανατολισμός των νανοδομών χειροτέρευε με αύξηση του μήκους τους καθώς κάμπτονταν και ενώνονταν με τα γειτονικά τους. Επομένως, για την βελτίωση της δομής τους βρέθηκε ότι είναι απαραίτητη η ανανέωση του διαλύματος κάθε ~2.30 h. Οι παραχθείσες νανοδομές εξετάστηκαν με ηλεκτρονική μικροσκοπία σάρωσης (SEM) και περίθλαση ακτίνων – Χ (XRD). Για την μελέτη των ατελειών στους κρυστάλλους του ZnO χρησιμοποιήθηκε η φασματοσκοπία Raman και η φασματοσκοπία φωτοφωταύγειας (Photoluminescence). Με την φασματοσκοπία Raman μελετήθηκαν οι τρόποι δόνησης των μορίων του υλικού, ενώ με τη φασματοσκοπία φωτοφωταύγειας η ύπαρξη ατελειών στον κρύσταλλο, όπως έλλειψη οξυγόνου, αντικατάσταση ψευδαργύρου με οξυγόνο, κλπ. / Zinc oxide (ZnO) is one of the most important low dimensional semiconducting oxides owing to the amazing variety of the nanostructures it can form by means of various synthesis routes. The most important methods are the vapor deposition and the chemical bath deposition. ZnO nanostructures have attracted considerable attention in view of several applications they encounter such as optics – optoelectronics, sensors, energy production, biomedical sciences, etc. Despite systematic research concerning the rational growth of ZnO nanostructures for over a decade, the establishment of an experimental methodology capable of providing specific morphologies of ZnO nanostructures in a reproducible way is still an open question. This is also one of the current research challenges because the resulting morphologies are characterized by different physical properties and are quite sensitive to small changes in experimental conditions. The current work is aimed at providing a systematic study of the role of various growth parameters on the morphological features and the optical properties of ZnO nanostructures. Growth was achieved by catalyst-assisted (Au) vapor transport at high temperature (VLS) and by solution chemistry (CBD). It is important to gain understanding about how certain parameters affect the morphology of the nanostructures, the size distributions of the diameters and their orientation relative to the substrate. High temperature evaporation methods, such as the vapor-liquid-solid mechanism, have been exploited for the controlled growth of ZnO nanostructures on various substrates. While Au is the most frequently used catalyst for growing ZnO nanowires, its morphological features on the substrate, which determine the size and shape of the nanostructures grown, are not yet methodically explored. In the current work, we investigated the details of thermal dewetting of Au films into nanoparticles on Si substrates. Au films of various thicknesses, h, ranging from 2 to 15 nm, were annealed under slow and fast rates at various temperatures and the morphological details of the nanoparticles formed were investigated. The vapor-liquid-solid method was employed to investigate the role of the Au nanoparticles on the growth details of ZnO nanowires. Efficient and high throughput growth of ZnO nanowires, for a given growth time, is realized in cases of thin Au films, i.e. when the thickness is lower than 10 nm. In the second case, the influence of a number of parameters such as the thickness of the seed layer, the reactants concentration, the existence of organic compounds, the growth time, etc. on the growth of ZnO nanowires on conducting glass substrates (FTO) was examined. After parameter optimization it was found that ZnO nanowires grown have excellent orientation, perpendicular to the substrate, while their diameter and length were found to be ~30 nm and ~7 μm, respectively. The best growth conditions were achieved using 0.04 Μ ZnAc, 0.02 M HMTA, 0.16 M PEI and 0.04 M NH4OH. The reaction temperature was kept at 95 οC for 1 h to 24 h. The pH value was ~ 7. The alignment of ZnO nanowires deteriorates when their length increases; therefore neighboring nanowires bend forming bundles. This shortcoming has been overcome by employing the renewal of the solution every 2.30 h. The structure of ZnO nanowires was investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Raman scattering was used to study defects of ZnO nanostructures. New Raman modes, in comparison to the bulk crystal, have been assigned to finite size effects and phonon confinement in the nanostructures. Photoluminescence spectroscopy provides evidence for the type of the defects such as oxygen vacancies, zinc interstitials etc.

Cycling of the relative humidity (RH) levels in the reactant streams of polymer electrolyte membrane (PEM) fuel cells has been reported to decay fuel cell performance. This study focuses on the accelerated durability testing to examine different modes of membrane failure via RH cycling. A single PEM fuel cell with an active area of 42.25 cm2 was tested. A Greenlight G50 test station was used to establish baseline cell (Run 1) performance with 840 hours of degradation under high-humidity idle conditions at a constant current density of 10 mA cm-2. Under the same conditions, two other experiments were conducted by varying the RH. For the H2-air RH cycling test (Run 2), anode and cathode inlet gases were provided as dry and humidified gases. Another RH cycling experiment was the H2 RH cycling test (Run 3): the anode inlet gas was cycled whereas keeping the other side constantly at full humidification. These two RH cycling experiments were alternated in dry and 100% humidified conditions every 10 and 40 minutes, respectively. In the experiments, the fuel cells contained a GoreTM 57 catalyst coated membrane (CCM) and 35 BC SGL gas diffusion layers (GDLs). The fuel cell test station had been performed under idle conditions at a constant current density of 10 mA cm-2. Under the idle conditions, operating at very low current density, a low chemical degradation rate and minimal electrical load stress were anticipated. However, the membrane was expected to degrade due to additional stress from the membrane swelling/contraction cycle controlled by the RH. In this work the performance of the 100% RH humidified cell (Run 1) was compared with that of RH cycling cells (Run 2 and Run 3). Chemical and mechanical degradation of the membrane were investigated using in-situ and ex-situ diagnostic methods. The results of each measurement during and after fuel cell operation are consistent. They clearly show that changing in RH lead to an overall PEM fuel cell degradation due to the increase in membrane degradation rate from membrane resistance, fluoride ion release concentration, hydrogen crossover current, membrane thinning, and hot-spot/pin-hole formation.