The automotive industry is constantly being challenged by customers and authorities to enhance the efficiency of the internal combustion engine (ICE) in order to achieve improved fuel consumption and reduced emissions. There are several interfaces within the design of an ICE that causes frictional losses, one of them is the valvetrain. An approach to reducing the friction in the valvetrain of modern engines is to implement cam-follower rollers, resulting in a rolling rather than sliding contact when interacting with the camshaft. The prominent type of wear in rolling contacts is surface fatigue, and specifically a phenomenon called micropitting. The company in collaboration with this project is Applied Nano Surfaces Sweden AB (ANS), located in Uppsala, Sweden. The company have specialized in surface treatment methods of mechanical components. ANS has developed a mechano-chemical treatment method called ANS Triboconditioning, which have shown beneficial friction and wear reducing properties when applied to metal surfaces. This thesis was conducted to investigate how the ANS Triboconditioning would affect the frictional behaviour compared to established surface treatment methods and the occurrence of micropitting in rolling contact configurations. Two types of test programs was implemented into a Wazau UTM 2000 Twin-Disc Tribometer. No clear trend could be established from the micropitting tests and therefore no conclusion regarding if ANS Triboconditioning affects the occurrence of micropitting damage in a positive or negative manner could be stated. The results from the friction test indicated an overall reduction in friction for the test specimens that had been treated with ANS Triboconditioning when compared to specimens that only had been treated with already established surface treatment methods. Summarized, additional tests and analyses are necessary in order to statistically confirm the observed results and determine their respective trends.

The papermaking industry uses a large amount of starch each year, both as a wet-end additive and as a rheological modifier in surface sizing and coating colors. It is important to be able to reduce the amount of chemicals used in the papermaking and surface treatment process, to reduce costs and to make the process even more efficient. Interest in new high-performance starches is great. By using these new types of starches, improved recycling of barrier products may be obtained as well as a reduction in the use of synthetic sizing agents. The objectives of this work were to understand the behavior of temperature-responsive hydrophobically modified starches, where the solubility in water simply can be adjusted by temperature or by polymer charge, to improve the barrier properties, like the water vapor permeability, mechanical properties and water resistance (Cobb and contact angle) of papers surface sized by starch-containing solutions, and to investigate the potential for industrial use of these temperature-responsive starches. It was demonstrated that the temperature-responsive starches phase separate upon cooling and, depending on the charge density of the starch, a particulate precipitation or a gel-like structure was obtained. The starch with zero net charge showed a larger increase in turbidity than the starch with a cationic net charge, indicating that particulate precipitation is favored by a zero net charge and that the formation of a gel network is favored by charged starch molecules. Further, the starches formed inclusion complexes with surfactants, giving stabilization to the starches in the presence of surfactants. The net charge density of the starch and the charge of the surfactant determined whether or not an inclusion complex would form between them. Important mechanisms for the stability of the starch seemed to be formation of mixed micellar-like structures between the hydrophobic chain of the starch and the surfactant along the starch backbone in addition to formation of inclusion complexes between the starch and the surfactant. The hydrophobically modified starches showed higher hydrophobic surface character when applied to the paper surface above the critical phase separation temperature than with application at room temperature. Free films of the temperature-responsive starches showed good barrier against oxygen, but no barrier against water vapor. The mechanical properties decreased with addition of glycerol to the films.

It is well known that thin coatings can provide increased lifetime and reduced energy consumption for tools and components. During use, e.g. in sliding contact, mechanical and chemical reactions often lead to the formation of new surface layers, tribofilms, possessing different properties compared to the original surface, hence affecting the overall performance. In this work, analytical electron microscopy was applied to investigate the structure and composition of tribofilms. Concerning coatings, deposition parameter dependencies, stability and tribology were investigated. The carbon content of hydrogen-free TiCx coatings was shown to significantly influence the morphology. Low carbon content resulted in columnar grains with a strong texture while high carbon content led to the formation of randomly ordered TiCx crystals. The application of positive bias to the substrate as opposed to the normally used negative bias gave a fibrous structure of sputtered TiB2 and low residual stress with maintained hardness. Further, oxidation stability was examined on a (Ta,Al)C:C coating where oxidation led to partial oxidation and formation of AlTaO4 with an 8 nm interface. A focused ion beam instrument was used to extract samples from certain areas of worn specimens. Tribological contact was observed to result in phase changes and intermixing of materials present in the contact. Sliding contact involving a Co-alloy led to a phase change from fcc to hcp. A 30 nm Co-rich tribofilm was observed with basal planes parallel to the surface. Fully formulated oil was found to inflict considerable wear to a metal doped carbon film through chemical reaction with the metal dopant. WC/Co cemented carbide used for rock drilling exhibited intermixing of rock and Co binder phase after field tests. Chemical vapour deposited diamond worn in nitrogen and argon showed formation of wear debris with amorphous structure containing nitrogen and graphitic like structure, respectively.

Bacteria primarily exist in robust, surface-associated communities known as biofilms, ubiquitous in both natural and anthropogenic environments. Mature biofilms resist a wide range of biocidal treatments and pose persistent pathogenic threats. Treatment of adherent biofilm is difficult, costly, and, in medical systems such as catheters, frequently impossible. Adding to the challenge, we have discovered that biofilm can be both impenetrable to vapors and extremely nonwetting, repelling even low surface tension commercial antimicrobials. Our study shows multiple contributing factors, including biochemical components and multiscale reentrant topography. Reliant on surface chemistry, conventional strategies for preventing biofilm only transiently affect attachment and/or are environmentally toxic. In this work, we look to Nature’s antifouling solutions, such as the dynamic spiny skin of the echinoderm, and we develop a versatile surface nanofabrication platform. Our benchtop approach unites soft lithography, electrodeposition, mold deformation, and material selection to enable many degrees of freedom—material, geometric, mechanical, dynamic—that can be programmed starting from a single master structure. The mechanical properties of the bio-inspired nanostructures, verified by AFM, are precisely and rationally tunable. We examine how synthetic dynamic nanostructured surfaces control the attachment of pathogenic biofilms. The parameters governing long-range patterning of bacteria on high-aspect-ratio (HAR) nanoarrays are combinatorially elucidated, and we discover that sufficiently low effective stiffness of these HAR arrays mechanoselectively inhibits ~40% of Pseudomonas aeruginosa biofilm attachment. Inspired by the active echinoderm skin, we design and fabricate externally actuated dynamic elastomer surfaces with active surface microtopography. We extract from a large parameter space the critical topographic length scales and actuation time scales for achieving nearly ~80% attachment reduction. We furthermore investigate an atomically mobile, slippery liquid infused porous surface (SLIPS) inspired by the pitcher plant. We show up to 99.6% reduction of multiple pathogenic biofilms over a 7-day period under both static and physiologically realistic flow conditions—a ~35x improvement over state-of-the-art surface chemistry, and over a far longer timeframe. Moreover, SLIPS is shown to be nontoxic: bacteria simply cannot attach to the smooth liquid interface. These bio-inspired strategies significantly advance biofilm attachment prevention and promise a tremendous range of industrial, clinical, and consumer applications. / Engineering and Applied Sciences

AISI 316L est un acier inoxydable couramment utilisé comme biomatériau grâce à des propriétés telles qu'une résistance à la corrosion élevée. Cependant, en cas d'attaque corrosive, ils sont susceptibles de libérer des ions métalliques qui peuvent provoquer des allergies. En outre, plusieurs défaillances d'implants ont été rapportées et reliées au fait que leur résistance à la corrosion localisée est néanmoins limitée. Dans ce sens, cette thèse vise à évaluer différentes approches visant à améliorer la résistance à la corrosion de l'acier inoxydable 316L pour des applications biomédicales à l'aide de deux stratégies: (1) la modification de la composition au sein de l'alliage et (2) la modification de la surface.La composition globale de l'acier inoxydable 316L a été modifiée avec l'addition d'azote. Des coulées ‘laboratoire' avec des compositions contrôlées ont été testées dans des milieux chloruré ainsi que dans des solutions physiologiques. L'effet de la combinaison de Mo et N sur le potentiel de piqûre s'est avéré supérieur à la somme de leurs effets individuels, ce qui indique une synergie. Cet effet, cependant, s'est montré dépendent du pH, étant fortement présent pour des milieux acides et neutres, tout en diminuant de façon importante avec l'augmentation du pH. Lors des essais dans des conditions physiologiques, cet effet était encore plus bénéfique avec le vieillissement. L'azote semble avoir amélioré la tendance à la répassivation de l'acier inoxydable avec Mo, déplaçant ainsi le potentiel de rupture du film passif vers des valeurs plus élevées.La surface de AISI 316L a aussi été revêtue avec de verres métalliques à basede fer à l'aide de laser cladding. Les revêtements ont donné des résultats différents en fonction de l'alliage. Les revêtements de Fe43.2Co28.8B19.2Si4.8Nb4 et Fe60Cr8Nb8B24 ont montré une matrice avec des ségrégations, en particulier de Nb, ce qui réduit leur résistance à la corrosion. D'autre part, le revêtement de Fe48.6Mo13.9Cr15.2C14.4Y1.8B6 s'est avéré être effectivement amorphe mais avec une résistance à la corrosion inférieure à celle du substrat, en raison de la présence de défauts.Ti et TiN ont également été revêtus sur les fils AISI 316L en utilisant un prototype de pulvérisation magnétron en mode défilé. Dans cette étude, les modesstatiques et semi-continus ont été utilisés. Globalement, la résistance à la corrosion des revêtements étaient plus faibles que celle du substrat, ce surtout avec l'augmentation de l'épaisseur du revêtement. La présence d'hétérogénéités de revêtement a permis l'interaction substrat-électrolyte, diminuant la résistance à la corrosion la corrosion et entrainant la délamination des revêtements avec le vieillissement. Des dépôts de phosphate de calcium ont été trouvés sur la surface du revêtement après 14 jours d'immersion, ce qui semble indiquer la possibilité de la croissance favorable de la matière osseuse. / AISI 316L stainless steel is commonly used as biomaterial because of its desirable properties such as high corrosion resistance. They have, however, the problem of releasing metal ions upon corrosion that may cause allergies to both humans and animals. In addition, implant failures have been reported due to their limited resistance to localised corrosion. There is thus a need to find ways to improve their corrosion resistance. This thesis aims to evaluate different approaches intending to improve the corrosion resistance of AISI 316L stainless steel for biomedical applications using two strategies: (1) modification of the bulk composition and (2) surface modification.The bulk composition of 316L-type stainless steel was modified by adding nitrogen. Laboratory grades with controlled compositions were tested in chloride conditions at a wide range of pH and in simulated physiological conditions. The combination of Mo and N on the pitting potential was found to be beyond the sum of their individual effects, indicating synergy. The effect, however, was found to be pH-dependent, being largely present in acid to neutral chloride conditions and in physiological solutions, while diminishing in high pH. When tested in physiological conditions, this effect was even more beneficial with ageing. Nitrogen was found to enhance the repassivation of the Mo-containing stainless steel grade, driving the potential for passive film breakdown to higher values.The surface of AISI 316L was coated with Fe-based metallic glasses using laser cladding. The resulting coatings had different results depending on the alloy. The coatings of Fe43.2Co28.8B19.2Si4.8Nb4 and Fe60Cr8Nb8B24 showed a matrix with segregations, particularly of Nb, thereby lowering their corrosion resistance. On the other hand, the Fe48.6Mo13.9Cr15.2C14.4Y1.8B6 coating was found to be amorphous but with lower corrosion resistance than the substrate, due to the presence of defects.Ti and TiN were also coated on AISI 316L wires using a prototype for magnetron sputtering in moving deposition mode. In this study, static and semi-continuous modes of motion were used. Overall, the corrosion resistance of the coatings were lower than the substrate, increasing further with coating thickness. The presence of coating heterogeneity allowed for substrate-electrolyte interaction, driving forward corrosion and delamination with further immersion. Deposits of calcium phosphate were found on the coating surface after 14 days of immersion, indicating the possible favourability of bone material growth.

Filmes de diamond like carbon (DLC) apresentam uma combinação única de propriedades, como alta resistência ao desgaste e ultra-baixo coeficiente de atrito. Porém, sua aplicação de forma mais difundida para melhorar a eficiência energética na indústria automobilística ainda é negligenciada devido à baixa adesão desse material em aço e também porque o mercado ainda não aceita o patamar atual de preço das tecnologias para solucionar esse problema. Adesão satisfatória do DLC em aço pode ser alcançada por meio de intercamadas nanométricas contendo silício, que são particularmente benéficas para a diminuição do alto stress compressivo que contribui para a delaminação do filme no substrato. A intercamada viabiliza a adesão do DLC em aço devido à formação de duas interfaces com ligações químicas diferentes e complementares. Intercamadas de Si foram depositadas em diferentes temperaturas, de 50 °C a 500 °C a partir de uma mistura hexametildisiloxano (HMDSO)/Ar e o filme de DLC foi depositado a 80 °C a partir de C2H2 por uma técnica DC-PECVD de baixo custo assistida por confinamento eletrostático. As análises da microestrutura e o mapeamento químico foram realizados por MEV e EDS, respectivemante. O perfil químico em função da profundidade realizado por GD-OES. Dureza e cargas críticas foram determinadas por ensaios de nanoindentação e nanoscratch. Resultados mostram melhor adesão à medida que se aumenta a temperatura de deposição da intercamada de SiCx:H. Com o aumento da temperatura ocorre a remoção de H e O, tornando a intercamada cada vez mais inomogênea, com C concentrado na interface externa, a-C:H/SiCx:H e Si na interface interna, SiCx:H/Aço. Essa reestruturação permite a formação de maior quantidade de ligações C-C, mais fortes do que Si-C, na interface externa, a-C:H/SiCx:H. No interior da intercamada, a remoção de H e O permite que ocorra difusão de C para dentro da intercamada durante a deposição do filme de a-C:H. Consequentemente se formam mais ligações Si-C, o que reduz o stress compressivo da intercamada, beneficiando a adesão. Finalmente, um modelo atomístico é proposto para explicar os mecanismos de ligação e descolamento do DLC. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-08-09T18:04:20Z No. of bitstreams: 1 Dissertacao Eigor Renato Petry.pdf: 6013116 bytes, checksum: 42c28a22f9a9b6c47e9593893f0e5ca1 (MD5) / Made available in DSpace on 2016-08-09T18:04:20Z (GMT). No. of bitstreams: 1 Dissertacao Eigor Renato Petry.pdf: 6013116 bytes, checksum: 42c28a22f9a9b6c47e9593893f0e5ca1 (MD5) Previous issue date: 2016-08-09 / Instituto Nacional de Engenharia de Superfícies / Diamond-like carbon thin films (DLC) show a unique combination of properties such as high wear resistance and ultra-low friction. However, a widespread use regarding energy efficiency issues in the automobile industry is neglected due to the poor adhesion of DLC on steel and/or expensive technologies. DLC adhesion on steel can be achieved by nanometric bonding interlayers containing silicon, which are particularly beneficial to mitigate the high compressive stress and the thin film mismatching, promoting stronger chemical bonds between the interfaces. The Si interlayers were deposited at different temperatures from 50 °C to 500 °C from a hexamethyldisiloxane (HMDSO)/Ar mixture and the DLC was deposited at 80 °C by a low-cost pulsed DC-PECVD technique assisted by electrostatic confinement. The microstructure and chemical mapping was analyzed by SEM and EDS. The chemical depth profiling was performed by GD-OES. Hardness and critical loads were analyzed by nanoindentation and nanoscratch tests. Results show better adhesion as substrate temperature is raised during the SiCx:H interlayer deposition process. As the deposition temperature is raised, H and O are removed from the structure, making the interlayer more inhomogeneous, with C concentrated on the outermost interface, a- C:H/SiCx:H and Si on the innermost interface, SiCx:H/Steel. This restructuring allows the formation of a higher quantity of C-C bonds at the outermost interface, which are stronger than Si-C bonds. Also, the removal of H and O allows C atoms to diffuse into the interlayer during the a-C:H coating deposition process. Consequently, more Si-C bond are formed on the bulk of the interlayer, reducing compressive stress and, thus, improving the adhesion of the a-C:H film. Finally, an atomistic model is proposed in order to explain the DLC bonding and debonding mechanisms.

No description available.

Filmes de diamond like carbon (DLC) apresentam uma combinação única de propriedades, como alta resistência ao desgaste e ultra-baixo coeficiente de atrito. Porém, sua aplicação de forma mais difundida para melhorar a eficiência energética na indústria automobilística ainda é negligenciada devido à baixa adesão desse material em aço e também porque o mercado ainda não aceita o patamar atual de preço das tecnologias para solucionar esse problema. Adesão satisfatória do DLC em aço pode ser alcançada por meio de intercamadas nanométricas contendo silício, que são particularmente benéficas para a diminuição do alto stress compressivo que contribui para a delaminação do filme no substrato. A intercamada viabiliza a adesão do DLC em aço devido à formação de duas interfaces com ligações químicas diferentes e complementares. Intercamadas de Si foram depositadas em diferentes temperaturas, de 50 °C a 500 °C a partir de uma mistura hexametildisiloxano (HMDSO)/Ar e o filme de DLC foi depositado a 80 °C a partir de C2H2 por uma técnica DC-PECVD de baixo custo assistida por confinamento eletrostático. As análises da microestrutura e o mapeamento químico foram realizados por MEV e EDS, respectivemante. O perfil químico em função da profundidade realizado por GD-OES. Dureza e cargas críticas foram determinadas por ensaios de nanoindentação e nanoscratch. Resultados mostram melhor adesão à medida que se aumenta a temperatura de deposição da intercamada de SiCx:H. Com o aumento da temperatura ocorre a remoção de H e O, tornando a intercamada cada vez mais inomogênea, com C concentrado na interface externa, a-C:H/SiCx:H e Si na interface interna, SiCx:H/Aço. Essa reestruturação permite a formação de maior quantidade de ligações C-C, mais fortes do que Si-C, na interface externa, a-C:H/SiCx:H. No interior da intercamada, a remoção de H e O permite que ocorra difusão de C para dentro da intercamada durante a deposição do filme de a-C:H. Consequentemente se formam mais ligações Si-C, o que reduz o stress compressivo da intercamada, beneficiando a adesão. Finalmente, um modelo atomístico é proposto para explicar os mecanismos de ligação e descolamento do DLC. / Instituto Nacional de Engenharia de Superfícies / Diamond-like carbon thin films (DLC) show a unique combination of properties such as high wear resistance and ultra-low friction. However, a widespread use regarding energy efficiency issues in the automobile industry is neglected due to the poor adhesion of DLC on steel and/or expensive technologies. DLC adhesion on steel can be achieved by nanometric bonding interlayers containing silicon, which are particularly beneficial to mitigate the high compressive stress and the thin film mismatching, promoting stronger chemical bonds between the interfaces. The Si interlayers were deposited at different temperatures from 50 °C to 500 °C from a hexamethyldisiloxane (HMDSO)/Ar mixture and the DLC was deposited at 80 °C by a low-cost pulsed DC-PECVD technique assisted by electrostatic confinement. The microstructure and chemical mapping was analyzed by SEM and EDS. The chemical depth profiling was performed by GD-OES. Hardness and critical loads were analyzed by nanoindentation and nanoscratch tests. Results show better adhesion as substrate temperature is raised during the SiCx:H interlayer deposition process. As the deposition temperature is raised, H and O are removed from the structure, making the interlayer more inhomogeneous, with C concentrated on the outermost interface, a- C:H/SiCx:H and Si on the innermost interface, SiCx:H/Steel. This restructuring allows the formation of a higher quantity of C-C bonds at the outermost interface, which are stronger than Si-C bonds. Also, the removal of H and O allows C atoms to diffuse into the interlayer during the a-C:H coating deposition process. Consequently, more Si-C bond are formed on the bulk of the interlayer, reducing compressive stress and, thus, improving the adhesion of the a-C:H film. Finally, an atomistic model is proposed in order to explain the DLC bonding and debonding mechanisms.

Cancer vaccines represent a promising treatment modality for a world-wide health problem. Whether as an adjuvant or as a stand-alone therapy, cancer vaccines represent a tumor-specific and systemic treatment potentially capable of eliminating metastatic lesions without the severe side-effects often associated with chemotherapy. Specifically, whole cell tumor vaccines have shown promise in preclinical and clinical settings and the studies presented here represent the beginnings of an approach to improve the antitumor potency of these vaccines. This project demonstrates as "proof of concept" the feasibility of manufacturing tumor cell-particle hybrids. The coupled use of these two components, whole tumor cells and cargo-carrying biodegradable particles, as one entity in a cancer vaccine system is a new line of research. Stable cell-particle hybrids were assembled using avidin-biotin chemistry where cargo-carrying PLGA particles (500 nm diameter) were coated with streptavidin and allowed to bind to tumor cells that had been indirectly labeled with biotin (using an integrin-specific biotinylated antibody). That successful cell-particle hybrids were assembled was determined by multiple means, including flow cytometry, laser scanning confocal microscopy and scanning electron microscopy. Two murine tumor cell lines (representing melanoma and prostate cancer) were investigated in this study and successfully demonstrated the general applicability of the assembly method. Particles appeared to be localized on the cell surface (rather than endocytosed) as determined by microscopic imaging. The cell-particle hybrid was shown to be stable to irradiation, an important consideration since whole tumor cells need to be treated with ionizing radiation prior to being used as vaccines in order to render them nonproliferative and immunogenic. We also characterized loading and release profiles of CpG, a prospective vaccine adjuvant, into PLGA particles. We conclude that we have developed a method for manufacturing cell-particle hybrids comprising PLGA nanoparticles and irradiated tumor cells. The next step would be to use CpG-loaded particles in the assembled hybrid and test the anti-tumor immune efficiency of this cancer vaccine formulation in either a melanoma or prostate cancer model.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19041号 / 農博第2119号 / 新制||農||1032(附属図書館) / 学位論文||H27||N4923(農学部図書室) / 31992 / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 植田 充美, 教授 渡邊 隆司, 教授 梅澤 俊明 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM