No description available.

In this study, we want to realize the influence of temperature and mechanical rubbing on the surface free energy and wettability of liquid crystal(LC) of polyimide(PI) thin films. In different surface conditions, we use the LC that was dropped on to the surface of the sample and become stable to explore the wettability of the surface. We also observe the phenomenon and influence of the LC on the PI with increasing surface temperature. We utilize hot stage and contact angle measuring system to obtain the surface free energy to realize the surface of the PI and measure the contact angle of LC in different temperature to realize the wettability of the PI. We found that the increase of the surface temperature leads to the decrease in the surface free energy of the PI and the contact angle of the FLC on the PI. The increase of the surface temperature causes the stabilization in the surface polar energy and the LC contact angle of the unrubbed PI. But the increase of the surface temperature causes the increase in the surface polar energy and the decrease of the LC contact angle of the rubbed PI. In the anti-parallel-direction to the rubbing direction the rubbed PI exhibits better wettability.

In this study we use PDMS thin films to fabricate of multi-domain surface. PDMS gets the characteristic of good physical properties and chemical, not only low surface free energy, flexible, also has low toxicity, low cost and can protect our environment. We used the DI water that was dropped on the PDMS thin film surface and became stable to explore the wettability of the surface, and we had a discussion about when liquid crystal dropped on the PDMS thin film surface. Then we also observe the phenomenon that was liquid crystal will shift a little distance and we used the optical image to analyze our device.

Mechanical Rubbing still is an useful alignment method in this time. In this study, we investigated the surface wettability of rubbed polyimide(PI) thin film. By using contact angle measurements, we found the surface free energy have strong connection with surface roughness in different rubbing times. We also discussed the wettability of rubbed PI thin film in parallel and anti-parallel of rubbing direction. We found that if we rubbed PI thin film 3 times in 0.3mm depth then the structure of SSFLC is more uniform than the alignment effect of other rubbing times and we found that the values of polar energy in parallel and anti-parallel of rubbing direction are very close. In the other part of study, we degenerated the polyimide before coating. We found that the reflection anisotropic spectrum(RAS) have a blueshift and the rubbing strength will be more influential in the wettability of PI thin film than the film with no degenerate process.

There are many heavy oil reservoirs with thin pay zones (less than 10 m) in the world and in Turkey. Conventional steam injection techniques are not costeffective for such reservoirs, due to excessive heat loss through the overburden. Heat losses can be minimized through controlled heating of the pay zone. One such way is to introduce heat to the reservoir in a controlled manner is microwave heating. Laboratory studies on microwave heating of a scaled model of a heavy oil reservoir with a thin pay zone are presented with an economical feasibility of the method. In this thesis, three different conceptual oil reservoirs from south east Turkey are evaluated: Bati Raman (9.5 API) and &Ccedil / amurlu (12 API) heavy crude oils and paraffinic Garzan (26 API)crude oil. Using a graphite core holder packed with crushed limestone with crude oil and water microwave effects of operational parameters like heating time and waiting period as well as rock and fluid properties like permeability, porosity, wettability, salinity, and initial water saturation are studied. The main recovery mechanisms for the experiments are viscosity reduction and gravity drainage. An analytical model is developed by coupling heat equation with the electromagnetic dissipated power per unit of volume based in Maxwell&#039 / s equation successfully models the experiments for temperatures less than the pyrolysis temperature is presented. Also the experiments are scaled to the model by geometric similarity concept. In economic evaluation, the cost of oil is calculated based on domestic electricity prices.

Carbonate rocks contain most of the world&rsquo / s proven hydrocarbon reserves. It is essential to predict flow properties and understand flow mechanisms in carbonates for estimating hydrocarbon recovery accurately. Pore network modeling is an effective tool in determination of flow properties and investigation of flow mechanisms. Topologically equivalent pore network models yield accurate results for flow properties. Due to their simple pore structure, sandstones are generally considered in pore scale studies and studies involving carbonates are limited. In this study, in order to understand flow mechanisms and wettability effects in heterogeneous carbonate rocks, a novel pore network model was developed for simulating two-phase flow. The constructed model was composed of matrix, fissure and vug sub domains and the sequence of fluid displacements was simulated typical by primary drainage followed by water flooding. Main mechanisms of imbibition, snap-off, piston like advance and pore body filling, were also considered. All the physically possible fluid configurations in the pores, vugs and fissures for all wettability types were examined. For configurations with a fluid layer sandwiched between other phases, the range of capillary pressures for the existence of such a layer was also evaluated. Then, results of the proposed model were compared with data available in literature. Finally, effects of wettability and pore structure on flow properties were examined by assigning different wettability conditions and porosity features. It was concluded that the proposed pore network model successfully represented two phase flow in fissured and vuggy carbonate rocks.

The current thesis was designed to examine the welding characteristics of laser and electron beam welding of the superplastic metal matrix composites (MMCs) reinforced with 1~20% SiC and to differentiate the difference between the 6061 aluminum alloy and 6061/SiC composites. The 6061/20%SiCw MMC was found to exhibit poor welding characteristics under electron beam welding. This was because that the SiC whiskers would induce poor fluidity of molten Al matrix and the electron beam continuously bombared the MMC resulting in material loss through sputtering, and this effect induced an "V" groove formed at the center of the fusion zone. The laser beam welding of the 20% SiCw MMCs caused the decomposition of the SiCw into Al4C3 platelets at the center region of the fusion zone, as well as cavities along the outer region due to thermal expansion differences. The post-weld tensile test results showed that the brittle weld zone lead to the degradation of strength, and the 6061/20%SiCw MMC after welding would lose superplastic properties. There were some differences between the 6061 alloy and MMC upon subjected to laser beam welding. The absorption of laser energy by the MMC was better than that by the alloy; the absorption of laser energy increased with increasing SiC content. The shape of the reinforced material could also influence the quantity of Al4C3 formed. The total surface area of SiC particles was smaller than that of the SiC whiskers under equal volume fraction, therefore more SiC whiskers were decomposed. In the wetting experiment, the wettability and fluidity of molten material was observed to decrease with increasing SiC volume fraction at the same temperature. The wettability could be improved at higher temperatures. For the 20%SiCw MMC, the wettability and fluidity could not be sufficiently improved even at a high temperature of 1300¢J, which appeared to be the cause for the lack of feeding in the central fusion zone.

In the present studies we investigated the effects of mechanical rubbing on the surface characteristics of polymer liquid crystal alignment layers. Contact angles of water droplets in contacted with the rubbed polyimide were measured using a surface tension meter, and the surface free energy of the polymer thin films were evaluated. We found that the contact angle of water and surface free energy on rubbed polyimide is anisotropic, and rubbing caused decrease in surface free energy and wettability of the polyimide surface. It was also seen that the contact angle hysteresis and the surface free energy measured in the direction parallel to the rubbing direction is smaller than that in the direction anti-parallel to the rubbing direction. We found that when the pile impression of the velvet fibers is 0.3 mm and the cumulative number of rub is 3 times, the contact angle hysteresis in direction parallel or anti-parallel to the rubbing direction will to be close. Be suitable choosing rubbing conditions, the SSFLCs without zigzag defects was produced. The pretilt angle and the response time of liquid crystal increased with the cumulative number.

Cellulose is a biodegradable, renewable, flexible, inexpensive, biopolymer which is abundantly present in nature. In spite of these inherent advantages, cellulose fibers cannot be used directly in a number of potential industrial applications because of their hydrophilic nature; a surface modification is often required to alter the surface properties of cellulose. This thesis work reports a fabrication method that results in superhydrophobic properties (contact angle (CA) > 150°) on cellulose (paper) surfaces. Superhydrophobicity was obtained by domain-selective etching of amorphous portions of the cellulose fiber in an oxygen plasma, and by subsequently coating the etched surface with a thin fluorocarbon film deposited via plasma enhanced chemical vapor deposition from a pentafluoroethane precursor. Two forms of superhydrophobicity with vastly different degrees of adhesion were obtained by varying the plasma treatment conditions, in particular the duration of oxygen etching: "roll-off" (contact angle (CA): 166.7° ± 0.9° and CA hysteresis: 3.4° ± 0.1°) and "sticky" (CA: 153.4° ± 4.7° and CA hysteresis: 149.8±5.8°) superhydrophobicity. The CA hysteresis could be tuned between the two extremes by adjusting the oxygen etching time to control the formation of nano-scale features on the cellulose fibers. The effects of fiber types (soft vs. hard wood) and paper making parameters on fabricating superhydrophobic paper were also investigated. There were no significant differences in the formation of the nano-scale features created via oxygen etching on paper substrates obtained from different fiber types and paper making parameters. Because "roll-off" superhydrophobicity is primarily determined by the nano-scale roughness, this property is therefore not significantly affected by the fiber types or paper making parameters. While the fiber type does not affect "roll-off" or "sticky" superhydrophobicity, paper making process parameters affect the structure of the paper web on the micro-scale and thus lead to variations in "sticky" superhydrophobicity. Superhydrophobic paper substrates were patterned with high surface energy ink deposited using a commercial desktop printer. The patterns could be used to manipulate the drag and extensional adhesion of water drops on the substrates. Classic 'drag' and 'extensional' adhesion expressions were used to model the behavior of water drops on basic dot and line patterns of variable dimensions. A fundamental understanding of the adhesive forces of water drops as a function of pattern shape and size was thus obtained. Based on this knowledge, patterned paper substrates were then designed and fabricated to perform simple unit operations, such as storage, transfer, mixing and merging of water drops. These basic functionalities were combined in the design of a simple two-dimensional lab-on-paper (LOP) device. Further studies of more complicated pattern shapes led to the generation of patterns that allowed directional mobility and tunable adhesion of water drops. These developments are critical for designing novel components for two-dimensional LOP devices such as flow paths, gates/diodes, junctions and drop size filters.

In this thesis detailed investigations of the phase behavior of poly(n-alkyl methacrylate-b-methyl methacrylate) diblock copolymers and its influence on the wettability of the polymer surfaces were carried out. For this investigation two polymethacrylic systems differing only in the alkyl rest of one block: poly(pentyl methacrylate-b-methyl methacrylate) and poly(propyl methacrylate-b-methyl methacrylate) have been chosen in order to prove how this substituent affects the phase behavior of whole system. The PnAlkMA-b-PMMA diblock copolymers in a wide range of molar masses, and with varied block length ratios were synthesized by living anionic polymerization. The syntheses were carried out in tetrahydrofuran (THF), at –78 °C, by using sec-buthyllithium as initiator, in the presence of lithium chloride (LiCl). Under these conditions highly syndiotactic products, rr ~ 0.82, with very narrow molar mass distribution, Mw/Mn ~ 1.1, were obtained. The phase behavior of PnAlkMA-b-PMMA diblock copolymers in bulk was investigated by means of DSC and SAXS measurements. The DSC analysis revealed that the PPMA-b-PMMA with weight fractions of PPMA, fPPMA, from 0.28 up to 0.86 showed two separate Tg’s, indicative of a phase separated system. However, by comparing the Tg’s of the diblock copolymers with the Tg’s of the corresponding homopolymers we found that in a few cases, mostly for samples with the high molar masses, they were slightly shifted. This finding pointed out the existence of two mixed phases, and hence partial miscibility between the both blocks was assumed. The SAXS patterns reflected for most diblock copolymers lamellae morphologies even in the case of very asymmetric composition, for instance with volume fraction of PPMA, 0.86 It was assumed that this behavior is caused by the chemical similarity of both blocks as well as by the differences in their molar volumes. The SAXS findings were further confirmed by the AFM measurements on the cutted “bulk” samples. From the solubility concept of Van Krevelen we obtained that the interaction parameter of PPMA-b-PMMA is rather low, 0.065, compared to the other well-known diblock copolymers. The calculated spinodals are characterized by a high asymmetry. The investigation of the phase behavior of PPMA-b-PMMA in thin films showed that the morphology as well as the topography of the thin films were strongly affected by the film thickness, when the films were prepared from a non-selective solvent (THF) onto silicon wafers. Well-recognizable nanostructures with long-range order were mainly found in thin films of diblock copolymers with high molar masses, above 100,000 g/mol, and with a high amount of PPMA. The lateral domain spacing obtained for these films from AFM corresponded well with that found in bulk. The study of the influence of the thermal as well as vapor annealing on the morphology and topography of the thin films provided additional information about the phase behavior of PPMA-b-PMMA diblock copolymers in thin films. Finally, the wettability of the investigated PPMA-b-PMMA surfaces was established by means of contact angle measurements. The measured contact angles were in most cases even on nicely nanostructured surfaces very similar to the contact angle of PPMA, indicating preferential segregation of PPMA to the film surface. Additional XPS measurements also showed an enrichment of the PPMA at the surface, independent of the morphology observed by AFM, and thereby confirmed the ADSA finding. In the next part of this work, investigations of the phase behavior of PPrMA-b-PMMA diblock copolymers were presented. In the contrary to the previous system the PPrMA-b-PMMA showed mostly a single Tg, which was further found to be depend on the weight fraction of PPrMA, fPPrMA. The SAXS data revealed that the PPrMA-b-PMMA diblock copolymers were phase separated in bulk, however the obtained scattering patterns exhibited mostly broad, not-well discernible higher-order peaks. Nevertheless, it was possible to identify the formed morphologies and depending on the volume fraction of PPrMA, hexagonally packed cylinders and lamellae were detected. The PPrMA-b-PMMA is characterized by a significantly lower value of the interaction parameter, 0.022, than the PPMA-b-PMMA system. This difference clearly reflects the weakening of the interactions between the components with decrease of the length of the alkyl side chain. The thin films of PPrMA-b-PMMA diblock copolymers appeared mostly smooth and featureless, independent of the film thickness. From the contact angle and XPS measurements we obtained, that unlike the PPMA-b-PMMA, both components were always present on the top of the surface. / In der vorliegenden Arbeit wurden Untersuchungen zum Entmischungsverhalten von Poly(n-alkylmethacrylat-b-methylmethacrylat) Diblockcopolymeren und deren Einfluss auf die Benetzbarkeit der Polymeroberflächen dargestellt. Diese Untersuchungen wurden anhand der Poly(pentylmethacrylat-b-methylmethacrylat) und Poly(propylmethacrylat-b-methylmethacrylat) durchgeführt. Die Diblockcopolymere in einem weiten Molmassenbereich, mit enger Molmassenverteilung, abgestuften Zusammensetzung wurden erfolgreich mittels anionischer Polymerization synthetisiert. Die Synthese erfolgte in THF bei (-78 °C) in Gegenwart von Lithiumchlorid. Als Initiator wurde sec. Butyllithium genutzt. Das Phasenverhalten der Diblockcopolymere im Festkörper wurde mittels DSC und SAXS untersucht. Für die meiste PPMA-b-PMMA Diblockcopolymere wurden mittels DSC zwei getrennte Tg gefunden, die aber im Vergleich zu den Tg von den entsprechenden Homopolymeren leicht verschoben waren. Es wurde also eine partielle Mischbarkeit der Blöcke festgestellt. Mittels SAXS-Untersuchungen wurde für die Mehrzahl der Diblckcopolymere in einem weiten Zusammensetzungsbereich bis zum 0.86 Volumenanteil von PPMA, eine lamellare Anordnung beobachten. Diese Befunde wurden nachfolgend mit AFM–Untersuchungen an dünnen Polymerfolien bestätigt. Das mit der Mean-Filed-Methode berechnete Phasendiagramm zeigte eine Asymmetrie, die durch die Unterschiede in den molaren Volumina des Blöckes verursacht war. Es wurde aber eine gute Übereinstimmung mit der experimentell erhaltenen Daten gefunden. Der berechnete für das System Wechselwirkungsparameter beträgt 0,065. Die AFM-Untersuchungen zum Entmischungsverhalten in dünnen Filmen haben gezeigt, dass die Topographie als auch Morphologie des Films war von der Filmdicke beeinflusst. Die Polymerfilme wurden mittels dipcoating der Si-Wafer präpariert. Dazu wurden Polymerlösungen in THF verwendet. Reguläre Nanostrukturen, deren Abstände mit dem im Festkörper gefundenen sehr gut übereinstimmten, wurden bei den Proben mit höherem Anteil von PPMA erhalten. Es wurden auch der Einfluss der Temperatur und der Dampfbehandlung auf die Morphologie und Topographie des Films untersucht. Die Benetzbarkeit der untersuchte PPMA-b-PMMA Filme wurde mit der Kontaktwinkelmessungen (ADSA) bestimmt. Als Messflüssigkeit wurde Milipore Wasser genutzt. Für die Mehrzahl der Diblockcopolymere wurden Kontaktwinkel im Bereich um 95° ermitteln, unabhängig von der Zusammensetzung der Diblockcopolymere und der vorhandenen Nanostruktur. Dies entspricht dem Kontaktwinkel von PPMA Homopolymer. Die Benetzbarkeit der PPMA-b-PMMA Filme wurde also durch die Oberflächensegregation des Niedrigenergieblocks (PPMA) bestimmt. Dies wurde danach durch zusätzliche XPS Messungen bestätigt. Im Vergleich zu PPMA-b-PMMA, die nachfolgend untersuchte PPrMA-b-PMMA Diblockcopolymere wiesen eine höhere Tendenz zur Mischbarkeit auf. Anhand der DSC–Untersuchungen wurde hier vorübergehend eine Misch-Tg gefunden. Nur bei der Probe mit symmetrischer Zusammensetzung wurden zwei getrennte Tg beobachtet. Die Streukurven von diesem System waren sehr schwach ausgeprägt. Dadurch die Indizierung der vorhandenen Morphologien war nicht eindeutlich. Der berechnete Wechselwirkungsparameter beträgt 0,022. Bei den AFM-Untersuchungen zum Entmischungsverhalten in dünnen PPrMA-b-PMMA Filmen wurden entweder keine oder sehr schwach geordnete Nanostruktur gefunden. Im Gegensatz zu dem vorherigen System, die Benetzbarkeit der PPrMA-b-PMMA Filme war durch die Zusammensetzung der Diblockcopolymere bedingt.