<p>The main objective for the work described in this PhD thesiswas to formulate a friction model to characterize thefrictional behavior of paper. More specifically, the modelshould explain a phenomenon that is typical for paper grades,viz.: that the level of paper-to-paper friction is dependent onthe direction and the number of previous slides. The modelshould also explain the lubricating effect oflow-molecular-mass lipophilic compounds (LLC) that occur inpaper on paper-to-paper friction. Furthermore, the model shoulddescribe the types of forces that influence paper-to-paperfiction and explain the mechanism by which the LLC decreasepaper-to-paper friction.</p><p>This thesis consists of a literature review of the basicconcepts of tribology and a summary of the main results andconclusions from four studies on the frictional characteristicsof paper and a study on the friction and adhesion of cellulosesurfaces together with some unpublished material.</p><p>The purpose of the investigation described in the firstpaper was to explain a phenomenon that is typical for papergrades, viz.: the level of paper-to-paper friction is dependenton the direction and the number of previous slides. Thisbehavior is called“friction hysteresis”by theauthors, and it has its origin in the reorientation of thefibers on the surface of a paper and their alignment relativeto the sliding direction.</p><p>The second paper describes a study that was aimed atidentifying lubricants that occur natively in paper. Filterpapers were impregnated with model compounds representing woodextractives, i.e. low-molecular-weight lipophilic compounds,which are present in wood, pulp and paper, and thepaper-to-paper friction was determined. The results of thatstudy show that a wood extractive must fulfill severalstructural criteria in order to lubricate a paper surface: Itmust have a hydrophilic group that can attach to the papersurface and a linear hydrocarbon backbone of sufficientlength.</p><p>Although it is not specifically stated in the second paper,the authors proposed a type of lubrication by which woodextractives decrease paper-to-paper friction that is, ineffect, boundary lubrication. The purpose of the investigationdescribed in the third paper was to clarify whether woodextractives and other low-molecular-mass lipophilic compoundsthat occur in paper can act as boundary lubricants on papersurfaces. The main objective of that study was to investigatethe role of chemical structure of LLC for their orientationrelative to the paper surface, which is an important criterionfor boundary lubrication. Filter papers were impregnated withmagnesium salts of different lipophilic acids, which were usedfor model compounds for the LLC. The deposited layers ofmagnesium salts were characterized by X-ray photoelectronspectroscopy (XPS) and contact angle goniometry and thefriction of the impregnated paper sheets was determined. Theresults show that the degree of lubrication and the resistanceto wear of the layers of a magnesium salt increased withincreasing chain length and increasing degree of linearity ofthe lipophilic acid. Based on the results of that study and ofearlier studies, it is concluded that boundary lubrication isthe type of lubrication by which low-molecular-mass lipophiliccompounds that occur natively in paper decreasepaper-to-paper-friction.</p><p>In boundary lubrication, surfaces are covered withmonolayers of lubricant molecules that comprise an active headgroup that can attach to the surface, e.g. a carboxyl group,and an inert linear backbone, such as a long saturatedhydrocarbon chain. Such compounds form ordered monolayers onsurfaces, so that the backbone points vertically out of planeof the surface. The friction is then determined by theinteractions between the monolayers, which are weaker than theinteractions between the clean surfaces and this gives a lowerfriction.</p><p>The fourth paper describes a study on the origin of thedifferences in friction levels between different linerboardsbased on recycled fiber (old corrugated container, OCC). Thesheets were subjected to two extraction stages and analyzedwith respect to surface roughness and their content oflow-molecular-mass lipophilic compounds (LLC). The resultsshowed that a high amount of LLC in the sheets lead to lowfriction, due to lubrication.</p><p>The fifth paper describes a study that was aimed atdetermining the types of forces that influence the frictionbetween the surfaces of hydrophilic polymers and explaining themechanism by which boundary lubricants decrease the friction.The adhesion and the friction of model systems was measuredwith atomic force microscopy (AFM) using regenerated cellulosefilms and functionalised AFM tips and the effect of fatty acidsand humidity was investigated. The friction significantlyincreased with increasing humidity and that there was a strongcorrelation between the ability of a fatty acid to form ahydrophobic surface and its lubricating performance. Measuredadhesion forces at high humidity were well predicted bytheoretical models that took into account the effect of theLaplace pressure acting in a water meniscus formed aroundcontact regions due to capillary condensation. The resultsindicated that the degree of capillary condensation may beeffectively suppressed by increasing the hydrophobicity of thecontacting surfaces, causing adhesion and friction to decrease.These results suggest that friction between paper surfacesunder ambient conditions is greatly influenced by the degree ofcapillary condensation. Furthermore, lubrication by fatty acidsis achieved by the formation of a vertically oriented,hydrophobic monolayer that can withstand the stresses duringsliding and increase the hydrophobicity of the paper surfaceand thereby suppress capillary condensation.</p><p><b>Keywords:</b>Friction, paper-to-paper friction, frictionhysteresis, fibers, orientation, sliding direction, woodextractives, low-molecular-mass lipophilic compounds, boundarylubrication, adhesion, capillary condensation, Laplacepressure, surface forces, JKR theory, gas chromatography-massspectroscopy, X-ray photoelectron spectroscopy, contact angle,atomic force microscopy</p>

No description available.

Advances in Vacuum Ultraviolet and X-ray Physics The 37th International Conference on Vacuum Ultraviolet and X-ray Physics (VUVX2010)

The surface behavior of biologically or atmospherically relevant chemical compounds in aqueous solution has been studied using surface-sensitive X-ray photoelectron spectroscopy (XPS). The aim is to provide information on the molecular-scale composition and distribution of solutes in the surface region of aqueous solutions. In the first part, the distribution of solutes in the surface region is discussed, where in particular single molecular species are studied. Concentration-dependent studies on succinic acid and various alkyl-alcohols, where also parameters such as pH and branching are varied, are analyzed using different approaches that allow the quantification of surface concentrations. Furthermore, due to the sensitivity of XPS to the chemical state, reorientation of linear and branched alkyl-alcohols at the aqueous surface as a function of concentration is observed. The results are further discussed in terms of hydrophilic and hydrophobic interactions in the interfacial region, where the three-dimensional hydrogen bonded water structure terminates. In the second part, mixed solutions of compounds, both ionic and molecular, are inspected. Again concentration, but also co-dissolution of other chemical compounds, are varied and differences in the spatial distribution and composition of the surface region are discussed. It is found that the guanidinium ion has an increased propensity to reside at the surface, which is explained by strong hydration in only two dimensions and only weak interactions between the aromatic π-system and water. Ammonium ions, on the other hand, which require hydration in three dimensions, are depleted from the surface region. The presence of strongly hydrated electrolytes out-competes neutral molecules for hydrating water molecules leading to an enhanced abundance of molecules, such as succinic acid, in the interfacial region. The partitioning is quantified and discussed in the context of atmospheric science, where the impact of the presented results on organic loading of aerosol particles is emphasized.

Ce travail de thèse est focalisé sur la détermination, de manière non-destructive, d'interfaces profondément enterrées dans des empilements multi-couches utilisés dans les conditions de technologie réelles au travers d'une méthode innovante basée sur la photoémission avec utilisation de rayons-x de haute énergie (HAXPES) et l'analyse du fond continu inélastique. Au cours de cette thèse, une procédure numérique a été développée pour quantifier la correspondance entre la mesure du fond continu faite par HAXPES et la simulation du fond continu représentative d'une distribution en profondeur donnée. Cette méthode permet de trouver la distribution en profondeur d'un élément grâce à une procédure semi automatisée. Dans un premier temps cette méthode a été testée en étudiant une couche ultra fine de lanthane enterrée à une profondeur >50 nm dans un dispositif de grille métallique high-k. L'influence des paramètres utilisés lors de l'analyse y est étudiée et révèle l'importance principale d'un paramètre en particulier, la section efficace de diffusion inélastique. La combinaison de mesures HAXPES avec l'analyse du fond continu inélastique utilisant cette nouvelle méthode permet d'augmenter la profondeur de sonde jusqu'à un niveau sans précédent. Ainsi l'échantillon peut être sondé jusqu'à 65 nm sous la surface avec une haute sensibilité à une couche nanométrique. Dans un second temps, la méthode précédemment validée d'analyse de fond continu inélastique est combinée avec une étude haute résolution des niveaux de cœur dans un échantillon servant de source dans un transistor à haute mobilité. Les deux analyses sont complémentaires puisqu'elles permettent d'obtenir la distribution en profondeur des éléments ainsi que leur environnement chimique. Le résultat donne une description complète des diffusions élémentaires dans l'échantillon suivant les différentes conditions de recuit. / This thesis tackles the challenge of probing in a non-destructive way deeply buried interfaces in multilayer stacks used in technologically-relevant devices with an innovative photoemission method based on Hard X-ray PhotoElectron Spectroscopy (HAXPES) and inelastic background analysis. In this thesis, a numerical procedure has been implemented to quantify the matching between a HAXPES measured inelastic background and a simulated inelastic background that is representative of a given depth distribution of the chemical elements. The method allows retrieving depth distributions at large depths via a semi-automated procedure. First, this method has been tested by studying an ultra-thin layer of lanthanum buried at depth >50 nm in a high-k metal gate sample. The influence of the parameters involved in the analysis is studied unraveling the primary importance of the inelastic scattering cross section. The combination of HAXPES with inelastic background analysis using this novel method maximizes the probing depth to an unprecedented level, allowing to probe the sample up to 65 nm below the surface with a high sensitivity to a nm-thick layer. Second, the previously-checked inelastic background analysis is combined with that of high resolution core-level spectra in the case of the source part of a high electron mobility transistor. The two analyses are complementary as they allow retrieving the elemental depth distribution and the chemical state, respectively. The result gives a complete picture of the elemental intermixing within the sample when it is annealed at various temperatures. / Denne afhandling omhandler problemet med at probe dybt begravede grænseflader i multilags stacks, som bruges i teknologisk relevante devices, med en innovativ fotoemissions metode, der er baseret på Hard X-ray PhotoElectron Spectroscopy (HAXPES) og analyse af den uelastiske baggrund. I afhandlingen er en numerisk procedure blevet implementeret til at kvantificere forskellen mellem en HAXPES målt uelastisk baggrund og en modelleret baggrund, som svarer til en given dybdefordeling af atomerne. Metoden muliggør, med en halv-automatisk procedure, at bestemme dybdefordelingen i store dybder. Metoden er først blevet testet ved at studere et ultra-tyndt lag af lanthan, som er begravet i en dybde > 50 nm i en high-k-metal-gate prøve. Indflydelsen af parametrene der ingår i analysen er blevet studeret for at opklare den primære betydning af det anvendte uelastiske spredningstværsnit. Kombinationen af HAXPES med analyse af den uelastiske baggrund og brug af den nye numeriske metode giver en hidtil uset probe-dybde, som giver mulighed for at probe den atomare sammens ætning i op til 65 nm dybde under overfladen og med høj følsomhed af et kun nm tykt lag. Dernæst er den uelastiske baggrundsanalyse blevet kombineret med højopløst core-level spektroskopi for at studere de aktive dele i en høj-elektronmobilitets transistor. De to analyser er komplementære, idet de henholdsvis bestemmer den atomare fordeling og atomernes kemiske bindingstilstand. Resultatet giver et fuldstændigt billede af atomernes omfordeling i prøven når denne opvarmes til forskellige temperaturer.

Electron cloud is an unwanted effect limiting the performance of particle accelerators with positively charged particle beams of high-intensity and short bunch spacing. However, electron cloud caused by beam induced multipacting can be sufficiently suppressed if the secondary electron yield (SEY) of accelerator chamber surface is lower than unity. Usually, the SEY is reduced by two ways: modification of surface chemistry and engineering the surface roughness. The objective of this PhD project is a systematic study of SEY as a function of various surface related parameters such as surface chemistry and surface morphology, as well as an effect of such common treatments for particle accelerators as beam pipe bakeout and surface conditioning with a beam, ultimately aiming to engineer the surfaces with low SEY for the electron cloud mitigation. In this work, transition metals and their coatings and laser treated surface were studied as a function of annealing treatment and electron bombardment. The transition metal thin films have been prepared by DC magnetron sputtering for further test. In the first two Chapter of this thesis, the literature review on electron emission effect is introduced, which includes the process of the electron emission, the influence factor and examples of low SEY materials. In the third Chapter, the experimental methods for SEY measurements and surface investigation used in this work are described. In Chapter 4, the SEY measurement setup which is built by myself are introduced in detail. In Chapter 5 transition metals and their coatings and non-evaporable getter (NEG) coatings have been studied. All the samples have been characterized by SEY measurements, their surface morphology was analysed with Scanning Electron Microscopy (SEM) and their chemistry was studied with X-ray Photoelectron Spectroscopy (XPS). Different surface treatments such as conditioning by electron beam, thermal treatment under vacuum on the sample surfaces have been investigated. For example, the maximum SEY (δmax) of as-received Ti, Zr, V and Hf were 2.30, 2.31, 1.72 and 2.45, respectively. After a dose of 7.9x10-3 C mm-2, δmax of Ti drops to 1.19. δmax for Zr, V and Hf drop to 1.27, 1.48 and 1.40 after doses of 6.4x10-3 C mm-2, 1.3x10-3 and 5.2x10-3 C mm-2, respectively. After heating to 350 °C for 2.5 hours, the SEY of bulk Ti has dropped to 1.21 and 1.40, respectively. As the all bulk samples have a flat surface, there are no difference of morphology. So this reduction of SEY is believed to be a consequence of the growth of a thin graphitic film on the surface after electron bombardment and the removal of the contaminations on the surface after annealing. Chapter 6 of this thesis is about the laser treated surface. Laser irradiation can transform highly reflective metals to black or dark coloured metal. From SEM results, metal surfaces modified by a nanosecond pulsed laser irradiation form a highly organised pyramid surface microstructures, which increase the surface roughness. Due to this reason, δmax of as-received laser treated surface could be lower than 1, which can avoid the electron cloud phenomenon. In this Chapter, the influence of different laser treatment parameters, such as power, hatch distance, different atmospheres on SEY has been investigated. Meanwhile, different surface treatments such as electron conditioning and thermal treatments are studied on the laser treated surface with the investigation of XPS. For example, the δmax of as-received type I with hatch distance 50, 60 and 80 μm in Air are 0.75, 0.75 and 0.80, respectively. After heating to 250 °C for 2 hours, in all case the δmax drop to 0.59, 0.60, 0.62, respectively. The SEYs of all as-received samples are lower than 1 due to the increasing the roughness on the surface by the special pyramid structure. After thermal treatment, the SEY reduces even further. This is caused by removing the contaminations on the surfaces. In conclusion, the present study has largely improved the knowledge of the electron cloud mitigation techniques by surface engineering of vacuum chambers. On the one hand, the surface treatments can modify the surface chemistry, such as the produce the graphic carbon layer on the surface by electron condition and the removal the contamination layer on the top of the surface by thermal treatment. On the other hand, the SEY could be critically low by engineering the surface roughness. Both methods allow reaching δmax less than unity. The efficiency of laser treated surface for e-cloud was demonstrated for a first time leading to a great interest to this new technology application for existing and future particle accelerators.

This thesis presents work based on the interactions of water soluble caboxylated zinc phthalocyanines (Pcs) and coreshell quantum dots (QDs). The Pcs are ZnPc(COOH)₈ and ZnPc(COOH)₄ and coreshell QDs are CdTe@ZnS-GSH. GSH = L-glutathione. Characterization and photophysical studies of conjugates were carried out. The approach of coordinating Pcs to QDs was achieved using an organic cross linker, N-N’-dicyclohexylcarbodiimide (DCC) at pH 10 at room temperature. Employing atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, infrared and X-ray photoelectron spectroscopies, the formation of the conjugates was confirmed. Upon conjugation with Pc derivatives, the fluorescence quantum yield of CdTe@ZnS-GSH decreased due to energy transfer from the QDs to the Pc. The average fluorescence lifetime of the CdTe@ZnS-GSH QD also decreased upon conjugation. The föster resonance energy transfer (FRET) behaviour of CdTe@ZnS-GSH-ZnPc(COOH)₄ conjugates was compared to that of CdTe@ZnS-GSH-ZnPc(COOH)₈. Higher FRET efficiencies were observed for CdTe@ZnS-GSH-ZnPc(COOH)₄-mixed or CdTe@ZnS-GSH-ZnPc(COOH)₄-linked compared to the corresponding CdTe@ZnS-GSH-ZnPc(COOH)₈-mixed or CdTe@ZnS-GSH-ZnPc(COOH)₈-linked. Triplet quantum yield (ΦT) and lifetime (ΤT) of ZnPc(COOH)₈ were found to increase in the presence of coreshell QDs. Though the singlet quantum yield (ΦΔ) value of ZnPc(COOH)8 was lower than ΦT , there was a slight upsurge in the ΦT in the presence of QDs. / Microsoft� Word 2010 / Adobe Acrobat 9.53 Paper Capture Plug-in

Doctor of Philosophy / Department of Chemistry / Peter M.A. Sherwood / This dissertation will examine the fabrication of different phosphorus containing films and their use as corrosion preventative films and adhesion materials between polymers and metal and metal alloys. Orthophosphate films are used in several metals and metal alloys to prevent corrosion and promote adhesion between paints or polymers and metal substrates. One key component is to examine the use of different phosphorus containing acids that might lead to phosphorus containing films which would compliment the mainly orthophosphate films currently in use. The objectives of this study are to see if it is possible to fabricate different phosphorus containing films, use them to adhere polymers to metal and metal alloys, and test the phosphorus containing films’ and polymer films’ corrosion protection properties. The thermoplastic resin, Poly(ether ketone ketone), or PEKK was found to adhere well to different phosphorus containing films and protect the underlying layers from oxidation in 4-D water. The phosphorus containing films were created by electrochemical deposition in different 5 M phosphorus containing acids. The metal or metal alloy was abraded to remove the native oxide and treated in the electrochemical cell. The second, separate polymer films were created by dip coating the metal or metal alloy in a polymer solution. The film thickness in both cases was controlled to be less than 100Å to ensure that the underlying metal or metal alloy could be detected. The surface chemical analysis was collected using X-ray photoelectron spectroscopy, or XPS. Core level and valence band XPS were used to distinguish the differences in the chemistry at the surfaces. The valence band XPS spectra were interpreted using spectra generated by multiple scattered wave calculations and band structure calculations. In the cases were more than one film was present subtraction and addition spectrum were used to interpret the chemistry in the interface region of the films.

Different approaches to surface modification were investigated in this work on gold, glassy carbon, multi-walled carbon nanotube paper and on single-walled carbon nanotubes adsorbed on glassy carbon. These approaches include electrochemical grafting, electropolymerisation, click chemistry, axial ligation, adsorption and self-assembled monolayers. The modified surfaces were characterised using a variety of techniques; predominantly electrochemistry, scanning electrochemical microscopy and X-ray photoelectron spectroscopy. For the formation of self-assembled monolayers on gold, four new manganese(III) phthalocyanines (1a-d), octa-substituted at the peripheral position with pentylthio, decylthio, benzylthio, and phenylthio groups were synthesized and characterised. X-ray photoelectron spectroscopy was used to show the formation of a sulphur-gold bond. A number of approaches using 4-azidoaniline (2a) combined with azide-alkyne click chemistry and electrochemistry were also used to anchor ferrocene and pyridine moieties on to the carbon surfaces, including direct in situ diazotation and grafting, electropolymerisation, and the synthesis of the diazonium salt followed by grafting. Iron phthalocyanine was linked to the pyridine-clicked surfaces through axial ligation, where the strong axial bond formed by the interaction between the central metal and the lone pair of the nitrogen in the pyridine group resulted in stable modified electrodes. The potential of these surfaces for the detection of analytes such as thiocyanate, hydrazine and sulphite are briefly shown as well. This work also describes for the first time the possibility of performing local micro-electrochemical grafting of a gold substrate by 4-azidobenzenediazonium (2b) using scanning electrochemical microscopy in a single and simple one step approach, without complications from adsorption.

No description available.